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Alt test range: Alcoholic hepatitis – Symptoms and causes


Alanine Aminotransferase (ALT, or SGPT)

What Is a Blood Test?

A blood test is when a sample of blood is taken from the body to be tested in a lab. Doctors order blood tests to check things such as the levels of glucose, hemoglobin, or white blood cells. This can help them detect problems like a disease or medical condition. Sometimes, blood tests can help them see how well an organ (such as the liver or kidneys) is working.

What Is an ALT Test?

An ALT test measures the level of alanine aminotransferase, also called ALT or SGPT. ALT is one of the enzymes that help the liver convert food into energy. High levels of these enzymes can be a sign that the liver is injured or irritated, and the enzymes are leaking out of the liver cells.

Why Are ALT Tests Done?

An ALT test may be done if a child has signs of a possible problem with the liver, such as jaundice (yellowish skin or eyes), dark urine, nausea, vomiting, or belly pain. It also might be done if a child is on medicine that makes high liver enzyme levels more likely.

How Should We Prepare for an ALT Test?

Your child may be asked to stop eating and drinking for 8 to 12 hours before the ALT test. Tell your doctor about any medicines your child takes because some drugs might affect the test results.

Wearing a T-shirt or short-sleeved shirt for the test can make things easier for your child, and you also can bring along a toy or book as a distraction.

How Is an ALT Test Done?

Most blood tests take a small amount of blood from a vein. To do that, a health professional will:

  • clean the skin 
  • put an elastic band (tourniquet) above the area to get the veins to swell with blood
  • insert a needle into a vein (usually in the arm inside of the elbow or on the back of the hand) 
  • pull the blood sample into a vial or syringe
  • take off the elastic band and remove the needle from the vein

In babies, blood draws are sometimes done as a “heel stick collection.” After cleaning the area, the health professional will prick your baby’s heel with a tiny needle (or lancet) to collect a small sample of blood.

Collecting a sample of blood is only temporarily uncomfortable and can feel like a quick pinprick.

Can I Stay With My Child During an ALT Test?

Parents usually can stay with their child during a blood test. Encourage your child to relax and stay still because tensing muscles can make it harder to draw blood. Your child might want to look away when the needle is inserted and the blood is collected. Help your child to relax by taking slow deep breaths or singing a favorite song.

How Long Does an ALT Test Take?

Most blood tests take just a few minutes. Occasionally, it can be hard to find a vein, so the health professional may need to try more than once.

What Happens After an ALT Test?

The health professional will remove the elastic band and the needle and cover the area with cotton or a bandage to stop the bleeding. Afterward, there may be some mild bruising, which should go away in a few days.

When Are ALT Test Results Ready?

Blood samples are processed by a machine, and it may take a few hours to a day for the results to be available. If the test results show signs of a problem, the doctor might order other tests to figure out what the problem is and how to treat it.

Are There Any Risks From ALT Tests?

An ALT test is a safe procedure with minimal risks. Some kids might feel faint or lightheaded from the test. A few kids and teens have a strong fear of needles. If your child is anxious, talk with the doctor before the test about ways to make the procedure easier.

A small bruise or mild soreness around the blood test site is common and can last for a few days. Get medical care for your child if the discomfort gets worse or lasts longer.

If you have questions about the ALT test, speak with your doctor or the health professional doing the blood draw.

Alanine Aminotransferase (Alt) – TSMP Medical Blog

Doctors often give the ALT test along with other liver tests.

ALT (Alanine Aminotransferase) Test

An alanine aminotransferase (ALT) test measures the level of the enzyme ALT in your blood. This test can help doctors evaluate liver function or determine the underlying cause of a liver problem.

ALT is an enzyme that is found mostly in the liver. The liver is the body’s largest gland. It has several important functions, including:

  • making proteins
  • storing vitamins and iron
  • removing toxins from your blood
  • producing bile, which aids in digestion

Proteins called enzymes help the liver break down other proteins so your body can absorb them more easily. ALT is one of these enzymes. It plays a crucial role in metabolism, turning food into energy. The ALT test is often part of an initial screening for liver disease.

ALT is normally found inside liver cells. However, when your liver is damaged or inflamed, ALT can be released into your bloodstream. This causes serum ALT levels to rise.

An increase in ALT is often the first sign of a liver problem, and ALT is often elevated before other symptoms appear.

An ALT test is also known as a serum glutamic-pyruvic transaminase (SGPT) test or an alanine transaminase test.

The ALT test is usually used to determine whether someone has liver injury or failure. Your doctor may order an ALT test if you’re having symptoms of liver disease, including:

  • jaundice, which is yellowing of your eyes or skin
  • dark urine
  • nausea
  • vomiting
  • pain in the right upper quadrant of your abdomen

Liver damage generally causes an increase in ALT levels. The ALT test can evaluate the levels of ALT in your bloodstream, but it can’t show how much liver damage there is or how much fibrosis, or scarring, is present.

The test also can’t predict how severe the liver damage will become.

An ALT test is often done with other liver enzyme tests. Checking ALT levels along with levels of other liver enzymes can provide your doctor with more specific information about a liver problem.

An ALT test may be part of a routine checkup or requested if someone has risk factors for liver disease, including:

  • family history
  • heavy alcohol use
  • exposure to hepatitis
  • taking certain medications
  • diabetes

Other reasons to perform an ALT test include:

  • monitoring the progression of liver diseases, such as hepatitis or liver failure
  • assessing whether treatment for liver disease should be started
  • evaluating how well treatment is working

An ALT test doesn’t require any special preparation. However, you should tell your doctor about any prescription or over-the-counter medications you’re taking. Some medications may affect the levels of ALT in your blood.

Your doctor might tell you to avoid taking certain medications for a period of time before the test.

An ALT test involves taking a small sample of blood, as outlined here:

  1. A healthcare professional uses an antiseptic to clean your skin in the area where they will take the sample.
  2. They will tie an elastic band around your upper arm, which stops the flow of blood and makes the veins in your arm more visible.
  3. Once they find a vein, they will insert a needle. This may cause a brief pinching or stinging sensation. The blood is drawn into a tube attached to the end of the needle. In some cases, more than one tube may be required.
  4. After enough blood has been collected, the healthcare professional removes the elastic band and the needle. They place a piece of cotton or gauze over the puncture site and cover that with a bandage or tape to keep it in place.
  5. The blood sample is sent to a laboratory for analysis.
  6. The laboratory sends the test results to your doctor. Your doctor may schedule an appointment with you to explain the results in more detail.

An ALT is a simple blood test with few risks. Bruising can sometimes occur in the area where the needle was inserted. The risk of bruising can be minimized by applying pressure to the injection site for several minutes after the needle is removed.

In very rare cases, the following complications can occur during or after an ALT test:

  • excessive bleeding where the needle was inserted
  • an accumulation of blood beneath your skin, which is called a hematoma
  • lightheadedness or fainting at the sight of blood
  • an infection at the puncture site

Normal results

According to the American College of Gastroenterology, the normal value for ALT in blood for people without risk factors for liver disease ranges from 29 to 33 international units per liter (IU/L) for males and 19 to 25 IU/L for females. This value can vary depending on the lab.

This range can be affected by certain factors, including sex and age. It’s important to discuss your specific results with your doctor.

Abnormal results

Higher-than-normal levels of ALT can indicate liver damage. Increased levels of ALT may be a result of:

  • hepatitis, which is an inflammatory condition of the liver
  • cirrhosis, which is severe scarring of the liver
  • death of liver tissue
  • a tumor or cancer in the liver
  • a lack of blood flow to the liver
  • hemochromatosis, which is a disorder that causes iron to build up in the body
  • mononucleosis, which is an infection usually caused by the Epstein-Barr virus
  • diabetes

Most lower ALT results indicate a healthy liver. However, studies have shown that lower-than-normal results have been related to increased long-term mortality. Discuss your numbers specifically with your doctor if you’re concerned about a low reading.

If your test results indicate liver damage or disease, you may need more testing to determine the underlying cause of the problem and the best way to treat it.

Last medically reviewed on June 7, 2021

What Is an Alanine Aminotransferease (ALT) Test?

The alanine aminotransferase (ALT) test is a blood test that checks for liver damage. Your doctor can use this test to find out if a disease, drug, or injury has damaged your liver.

Your liver does a lot of important things for you:

  • It makes a fluid called bile that helps your body digest food.
  • It removes waste products and other toxins from your blood.
  • It produces proteins and cholesterol.

Diseases such as hepatitis and cirrhosis can damage your liver and prevent it from doing its many jobs.

Why Is ALT Important?

This enzyme is found mainly in your liver. Smaller amounts of ALT are in your kidneys and other organs, too.

Your body uses ALT to break down food into energy. Normally, ALT levels in the blood are low. If your liver is damaged, it will release more ALT into your blood and levels will rise. (ALT used to be called serum glutamic-pyruvic transaminase, or SGPT).

Doctors often give the ALT test along with other liver tests.

Why Would My Doctor Order This Test?

Your doctor might recommend ALT if you have symptoms of liver disease or damage, such as:

  • Stomach pain or swelling
  • Nausea
  • Vomiting
  • Yellow skin or eyes (a condition called jaundice)
  • Weakness
  • Extreme tiredness (fatigue)
  • Dark-colored urine
  • Light-colored poop
  • Itchy skin

Here are some reasons you might get this test:

  • You’ve been exposed to the hepatitis virus.
  • You drink a lot of alcohol.
  • You have a family history of liver disease.
  • You take medicine that’s known to cause liver damage.

The ALT test can be done as part of a blood panel during a regular exam. If you’ve already been diagnosed with liver disease, your doctor can use the ALT test to see how well your treatment is working.

How Do I Prepare?

You don’t need any special preparation for the ALT test. Your doctor might ask you to stop eating or drinking a few hours before the test.

Tell your doctor what prescription drugs or supplements you take. Some medicines can affect the results of this test.

What Happens During the Test?

A nurse or lab tech will take a sample of your blood, usually from a vein in your arm. They will first tie a band around the upper part of your arm to make your vein fill with blood and swell up. Then they will clean the area with an antiseptic and place a needle into your vein. Your blood will collect into a vial or tube.

The blood test should take only a couple of minutes. After your blood is taken, the lab tech will remove the needle and band, then put a piece of gauze and a bandage over the spot the needle went in to stop the bleeding.

What Are the Risks?

The ALT blood test is safe. Risks are usually minor, and can include:

  • Bleeding
  • Bruising
  • Infection
  • Slight pain when the needle is inserted
  • Fainting or feeling dizzy

What Do the Results Mean?

You should get your results in about a day. A normal ALT test result can range from 7 to 55 units per liter (U/L). Levels are normally higher in men.

Slightly high ALT levels may be caused by:

  • Alcohol abuse
  • Cirrhosis (long-term damage and scarring of the liver)
  • Mononucleosis
  • Drugs such as statins, aspirin, and some sleep aids

Moderately high ALT levels may be because of:

  • Chronic (ongoing) liver disease
  • Alcohol abuse
  • Cirrhosis
  • Blockage of the bile ducts
  • Heart attack or heart failure (when your heart can’t pump enough blood to your body)
  • Kidney damage
  • Muscle injury
  • Damage to red blood cells
  • Heat stroke
  • Too much vitamin A

Very high ALT levels can be caused by:

  • Acute viral hepatitis
  • An overdose of drugs such as acetaminophen (Tylenol)
  • Liver cancer
  • Sepsis

What Other Tests Will I Take?

ALT usually is done as part of a group of liver function tests called a liver panel.

This panel also includes an aspartate aminotransferase (AST) test. AST is another liver enzyme. As with ALT, the levels of AST in your blood rise if your liver is damaged.

Comparing ALT with AST levels gives your doctor more information about the health of your liver. The ALT-to-AST ratio can help your doctor figure out how severe the liver damage is and what might have caused it.

To find out what type of liver disease you have, your doctor might also test the levels of other enzymes and proteins found in your liver, including:

  • Albumin
  • Alkaline phosphatase
  • Bilirubin
  • Lactate dehydrogenase (LDH)
  • Total protein

Talk to your doctor to make sure you understand all of your liver test results. Also find out how these results might affect your treatment.

Show Sources

American Association for Clinical Chemistry: “ALT.”

Mayo Clinic: “Liver Disease: Definition.” “Liver function tests.”

Medscape: “Alanine Aminotransferase.

National Heart, Lung, and Blood Institute: “What To Expect With Blood Tests.”

Nemours Foundation: “Blood Test: Alanine Aminotransferase (ALT, or SGPT).”

University of Rochester Medical Center: “ALT.”

Alanine Transaminase (ALT)

Alanine transaminase (ALT) is an enzyme that mainly exists in your liver. An ALT blood test is often included in a liver panel and comprehensive metabolic panel, and healthcare providers use it to help assess your liver health. High levels of ALT in your blood may indicate that you have damage to your liver and/or a liver condition.

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What is alanine transaminase (ALT)?

Alanine transaminase (ALT), also known as alanine aminotransferase, is an enzyme that’s mainly found in your liver, though it exists in other parts of your body.

An enzyme is a type of protein in a cell that acts as a catalyst and allows certain bodily processes to happen. There are thousands of enzymes throughout your body that have important functions.

What is an ALT blood test?

An alanine transaminase (ALT) blood test measures the amount of ALT in your blood. ALT levels in your blood can increase when your liver is damaged, so healthcare providers often use an ALT blood test to help assess the health of your liver.

Since many types of liver problems can cause ALT levels to increase, healthcare providers don’t use the test alone to diagnose conditions. An ALT blood test is most often included in a blood test panel, such as a liver enzyme panel (HFP or LFT) or a comprehensive metabolic panel (CMP). A blood panel measures several aspects of your blood with one sample and can provide more detailed information about your overall health.

Common names for an ALT blood test include:

  • Alanine transaminase (ALT).
  • Alanine aminotransferase.
  • SGPT.
  • Serum glutamic-pyruvic transaminase.
  • GPT.

How is alanine transferase (ALT) different from aspartate transferase (AST)?

Aspartate transferase (AST) is another enzyme that’s commonly measured along with AST in a liver function panel or comprehensive metabolic panel. Both of these enzymes can leak into your bloodstream when certain cells in your body are damaged.

AST and ALT are both commonly considered liver enzymes, but there are greater amounts of AST in other parts of your body, such as your heart, skeletal muscles and pancreas. Because of this, ALT is considered to be more directly tied to your liver health, but healthcare providers use both measurements to assess the health of your liver.

Why do I need an ALT blood test?

The purpose of an ALT blood test is to help evaluate the health of your liver. If cells in your liver are damaged, it can cause ALT to leak into your blood, so an ALT blood test can help find liver issues.

Your healthcare provider may order a blood panel test that includes an ALT test for you to help screen for, monitor or help diagnose liver conditions.


Screening means checking for potential health issues before you experience symptoms. Your healthcare provider will likely recommend screening with a liver panel blood test that includes an ALT test if you have risk factors for liver disease, which include:

  • Heavy alcohol use.
  • Family history of liver disease.
  • Diabetes.
  • Obesity.
  • Injecting drugs using shared needles.

Since ALT tests are often included in routine blood panel tests that assess your general overall health, such as a comprehensive metabolic panel (CMP), you may have an ALT test even if you don’t have risk factors for liver disease.


If you have a liver condition, your provider may order an ALT test, often as part of a panel, to monitor your condition to see if it’s improving, worsening or staying the same with or without treatment. Your provider may also have you undergo an ALT test and liver enzyme panel test if you’re taking a medication that can affect your liver health.


Your provider may use an ALT test for diagnostic purposes when you’re experiencing signs and symptoms of possible liver problems. While providers can’t diagnose a condition based solely on ALT levels, it can be an important part of the diagnostic process.

Signs and symptoms of liver conditions include:

  • Nausea and/or vomiting.
  • Belly (abdominal) pain.
  • Itchy skin.
  • Jaundice (a yellowing of your skin and the whites of your eyes).
  • Tiredness (fatigue).
  • Appetite loss.

Test Details

Who performs an ALT blood test?

A healthcare provider called a phlebotomist usually performs blood draws, including those for an ALT blood test, but any healthcare provider trained in drawing blood can perform this task. The samples are sent to a lab where a medical laboratory scientist prepares the samples and performs the test on machines known as analyzers.

Do I need to fast for an ALT blood test?

If your ALT test is part of a comprehensive metabolic panel (CMP), you’ll likely need to fast for 10 to 12 hours before your CMP blood test. Fasting means not eating or drinking anything other than water.

It’s not as common, but if you’re only getting an ALT blood test, you don’t need to fast.

In any case, your healthcare provider will give you instructions when they order the bloodwork. Be sure to follow their directions.

Do I need to do anything to prepare for an ALT blood test?

Many different types of medications and supplements can affect your ALT levels, so it’s important to tell your healthcare provider about any drugs or dietary supplements you’re taking before you get the test. In some cases, your provider may have you stop taking a medication before the test. Only stop taking medication if your provider tells you to do so.

Intense exercise can also affect your ALT levels, so tell your provider if you frequently do demanding physical workouts before you get the ALT test.

What should I expect during my ALT blood test?

You can expect to experience the following during a blood test, or blood draw:

  • You’ll sit in a chair, and a healthcare provider will check your arms for an easily accessible vein. This is usually in the inner part of your arm on the other side of your elbow.
  • Once they’ve located a vein, they’ll clean and disinfect the area.
  • They’ll then insert a small needle into your vein to take a blood sample. This may feel like a small pinch.
  • After they insert the needle, a small amount of blood will collect in a test tube.
  • Once they have enough blood to test, they’ll remove the needle and hold a cotton ball or gauze on the site to stop any bleeding.
  • They’ll place a bandage over the site, and you’ll be finished.

The entire procedure usually takes less than five minutes.

What should I expect after my ALT blood test?

After a healthcare provider has collected your blood sample, they’ll send it to a laboratory for testing. Once the test results are back, your healthcare provider will share the results with you.

What are the risks of an ALT blood test?

Blood tests are a very common and essential part of medical testing and screening. There’s very little risk to having blood tests. You may have slight tenderness or a bruise at the site of the blood draw, but this usually resolves quickly.

When can I expect the results of my ALT blood test?

In most cases, you should have your test results within one to two business days, though it could take longer.

Results and Follow-Up

What do the results of an ALT blood test mean?

Blood test reports, including alanine transaminase (ALT) test reports, usually provide the following information:

  • The name of the blood test or what was measured in your blood.
  • The number or measurement of your blood test result.
  • The normal measurement range for that test.
  • Information that indicates if your result is normal or abnormal or high or low.

What is the normal range for an ALT blood test?

The normal range for alanine transaminase (ALT) varies from laboratory to laboratory. One common reference range for an ALT blood test is 7 to 56 U/L (units per liter). ALT levels are typically higher in people assigned male at birth than in people assigned female at birth.

Since ranges can vary depending on the laboratory, it’s important to check your test result report to see what your specific lab’s reference range is.

What does it mean if my alanine transaminase (ALT) is high?

High levels of ALT in your blood can be due to damage or injury to the cells in your liver. An increased ALT level may indicate the following conditions:

  • Alcohol-induced liver injury.
  • Fatty liver disease (too much fat in your liver).
  • Hepatitis (liver inflammation).
  • Cirrhosis (scarring of the liver).
  • Taking medications that are toxic to your liver.
  • Liver tumor or liver cancer.
  • Liver ischemia (not enough blood flow to your liver, which leads to death of liver tissue).
  • Hemochromatosis (having too much iron in your body).
  • Mononucleosis (“mono”).
  • Certain genetic conditions can affect your liver.

Although it’s less common, elevated ALT levels can also indicate injury to cells in other parts of your body, since ALT isn’t solely found in your liver.

It’s important to know that having a high ALT test result doesn’t necessarily mean you have a medical condition. Less than 5% of people with elevated ALT levels have severe liver conditions. Other factors can affect your ALT levels. Your provider will take into consideration several factors, including other blood test results and your medical history, when analyzing your results.

What does it mean if my alanine transaminase (ALT) is low?

Having a lower than normal ALT result is uncommon and usually isn’t a cause for concern. However, a lower than normal ALT level could indicate a vitamin B6 deficiency or chronic kidney disease.

If your ALT result is lower than what’s considered normal, your healthcare provider will likely have you retake the test or undergo further testing to make sure nothing is causing your low level.

Should I be worried if I have high or low alanine transaminase (ALT) test results?

If your ALT test result is high or low, it doesn’t necessarily mean that you have a medical condition that needs treatment. Other factors can affect your levels, including:

  • Exercise: Intense or extreme exercise can cause a temporary increase in ALT levels.
  • Medications: Several medications and supplements can affect ALT levels, including over-the-counter pain medications such as acetaminophen.
  • Sex: Scientists believe hormonal differences contribute to sex differences in ALT levels.
  • Menstruation: ALT levels can increase or decrease during your menstrual cycle.
  • Age: ALT levels tend to decrease with older age.
  • Heritage: Research shows that people who have Mexican-American heritage are more likely to have elevated levels of ALT.
  • Body mass index: Several studies have revealed an association between ALT levels and body mass index (BMI), which may change the interpretation of test results in people who have obesity.

In addition to the above factors, when analyzing your ALT results, your healthcare provider will take into consideration many aspects of your health and situation, including:

  • Your medical history.
  • How high or low your ALT results are.
  • Previous ALT results.
  • The results of other tests usually taken alongside ALT.
  • If you’re experiencing symptoms.

Do I need follow-up tests if my ALT results are abnormal?

It’s common for healthcare providers to recommend follow-up tests if you have an abnormal ALT level.

Follow-up testing may include:

  • Repeat ALT blood tests.
  • Other blood tests.
  • Imaging tests.
  • A biopsy.

Additional testing may be immediate if you have significantly elevated ALT levels and/or are experiencing symptoms of a liver condition.

Every person and situation is unique, so there’s no single follow-up testing plan that works for everyone. Together, you and your provider will determine the best plan.

When should I call my doctor?

If you’re experiencing symptoms of liver damage, such as jaundice or belly pain, call your healthcare provider.

If you’ve been diagnosed with a liver condition and are experiencing new or concerning symptoms, contact your provider.

If you have any questions about your alanine transaminase (ALT) results, don’t be afraid to ask your provider questions.

A note from Cleveland Clinic

Seeing an abnormal test result can be stressful. Know that having a high level of alanine transaminase (ALT) doesn’t necessarily mean you have a medical condition and need treatment. Many factors can affect your ALT levels, and 1 in 20 healthy people will have results outside of the normal range. Your healthcare provider will let you know if you need to undergo further tests to determine the cause of the abnormal level. Don’t be afraid to ask your provider questions. They’re there to help you.

how to simplify testing mobile games with a minimum of costs / Sudo Null IT News

Testing is an integral part of game development, and mobile titles are no exception. The market is full of devices of a wide variety of form factors, power and compatibility. Moreover, the more players, the more successful the game and the more income. In order to have as many players as possible, support for the maximum number of smartphones and tablets is needed. To achieve this, you need to “polish the build” to work even on the most budget devices.

Since testing is necessary, the question arises: how to carry it out? The easiest way is to collect a pool of devices and run the game on them, track bugs and fix them. The method is reliable, but it is highly dependent on the number of testers, and requires a larger amount of costs, because. there is a risk of loss or damage to devices. Bug tracking is also difficult in physical testing, as here the information for the developer is determined only by how responsibly the tester approaches the process.

It is possible and necessary to speed up, optimize and automate the process. You can do this by setting up a test farm. My name is Maxim Shagov, I work as a QA lead in mobile game publishing and I will tell you how to do it and what it is.

What is it?

In short, the farm is a test PC, similar to those on which computer games are tested, only there is no video card (not needed), and the rest of the hardware is more budget. The purpose of this installation is to create a place where an employee can get a device to test the game without direct physical access to it.

This is especially useful if the company has a large fleet of devices, and keeping track of them is quite difficult. The more employees, the more difficult, because everyone needs a device. The farm, on the other hand, allows you to keep devices connected all the time, and issue them to employees without unnecessary delays and bureaucracy.

How does it work?

For the user, the operation of the farm is similar to the operation of the remote play functions found on some game consoles. All smartphones and tablets are connected to a farm deployed on Ubuntu. In our case, we based it on source code available for free on GitHub, which was refined and optimized for the needs of the company, and also updated since the original developer stopped supporting 4-5 years ago. At the moment, the farm supports all versions of Android, up to the 12th. Work on iOS support is also underway.

The principle of operation in detail looks like this: on the basis of Ubuntu, a server is deployed that uses Rethink as a database. The choice of Ubuntu is simply explained – it is best suited for work due to its functionality. The user is connected to the devices via the web interface, and the devices themselves are connected to the PC via the Android Debug Bridge. It shows each specific session of each user on that or device at the current time. The administrator has access to the history of all operations. You can even connect to the interface from a smartphone and use it to test another device, for example, log in from an iOS smartphone and work on an Android tablet.

Considering that the work is essentially carried out through a web connection, the question may arise: “Will a weak connection cause difficulties in operation?”. As our tests have shown, such an installation does not require a heavy-duty connection, even quite a budget connection of 100 Mbps is suitable, and up to 120 people can work with it at the same time.

What is the benefit for the developer?

First, as already mentioned, the more devices that support the game, the better. Testing on a large fleet of different devices is the best way to ensure this support. The farm allows you to significantly speed up and simplify the process, including facilitating access to smartphones and tablets.

Secondly, this does not tie testing to the company’s office. The employee does not need to take the device physically, which means there is no need to stay with him at the workplace, in order to avoid loss or violation of non-disclosure agreements. You can connect for testing both from a working PC and from your own device, observing proper security measures.

Third, test devices are easier to control through the farm. It tracks who, where and when takes which smartphone, which helps to optimize the schedule and determine the possible causes of errors and crashes.

Fourth, the farm supports macros, which allows you to simultaneously test the same game session on different devices. This greatly reduces testing time and labor costs for employees. Alternative methods, such as emulation, do not always cover such needs.

Finally, through the farm you can record videos and take screenshots automatically. This helps in case of crashes or some problems immediately attaching confirmations to error reports.

There are, of course, disadvantages, but they are rather individual. For example, for each form factor and devices with different resolutions, you need to record macros individually. The more macros, the more support is required. We are currently working on a solution to this problem.

In the future, we also plan to bring the system to duplication of sessions from one device to the rest via Wi-Fi, and removing logs from all of them at the same time through it. This will allow you to test all devices at once from one device from anywhere in the office.

How to make your own farm?

“Really simple recipe”. The solution is available to both indie developers and large companies. For example, we use an i7-based PC for the farm, with 32 GB of RAM, a 500 GB SSD and a 2 TB hard drive for recording logs, screenshots and videos. In addition, you will need Ubuntu 20.0.4 and docker, where you install a container with a ready server, in order to restart the farm in case of failure. The latter is very easy to do, even a novice specialist can do it. The server can be deployed on less powerful systems, it all depends on the number of devices and frequency of use.

As for individual revision, it can be carried out by any employee with the level of training of a system administrator. Refinement occurs iteratively, and this is a continuous process, but the bulk of the installation and configuration work is carried out in a short time. In our case, the study of the material took 1 month, and the server itself was deployed in 4 working days.

How does it work?

For the user, working with the farm is similar to working on the devices themselves. It looks like running in an emulator, but only using phone resources. At the same time, the farm administrator sees all sessions in real time and can view the logs at any time, which significantly saves time, because. the reason for the “crash” of the application becomes known almost immediately.

All smartphone features are supported, including multiple languages, keyboard input, multi-touch, and gestures. The devices themselves are located in a special box in the immediate vicinity and they can be tracked, including physically.

Won’t this kill devices faster?

Of course, additional load is created, primarily due to the connection in debug bridge mode, which affects the battery. According to manufacturers, the service life of the device in such conditions can be reduced by 20%. However, in practice, this does not play a big role, especially given the speed with which the market updates devices – they need to be replaced more often to avoid falling behind competitors than due to device failure. However, it is still worth having a stock of spare parts and batteries.

Who would be best suited to work on a farm? Which of the developers should take a closer look, and who should not?

Such a solution may not be suitable only for highly targeted teams, but the big question is whether such teams still exist in our time. Android has a large pool of devices and a wide range of concurrently supported OS versions. With iOS, the situation is more or less similar. Therefore, a farm is a much more convenient option. A properly selected fleet of devices will optimize operation for the widest possible range. The company will be able to more quickly identify errors and fix them, reducing time costs, which is especially important in an industry where the game must be in perfect condition before release, otherwise players lost at the start may not return.

Frequency band extension devices

The first part of the article.

When measuring S-parameters from a network analyzer, a test sinusoidal signal of the required frequency is applied to the input port of the device under test (DUT), the reflected signal at the input and the transmitted signal that was transmitted through the device to the output port are measured. These signals differ in amplitude and phase from the test signal.

Network analyzer (AD) is designed to measure the complex transmission and reflection coefficients (S-parameters) of radio engineering devices.

In fact, the AD is a device that measures the characteristics of the signal passing through the device under test and the characteristics of the reflection of the signal from its ports, called S-parameters [2]:

  • reflection coefficient – the ratio of the reflected signal to the incident signal;
  • transmission coefficient – the ratio of the transmitted signal to the incident signal.

For 2-port devices, these specifications are shown in fig. 12:
S11 – reflection characteristic from the first port;
S21 – transmission characteristic in the forward direction;
S12 – transmission characteristic in the opposite direction;
S22 Port 1 reflection.

12. Determination of the main four S-parameters of the device under test

When measuring a pair of parameters S11 and S21, port 1 acts as a signal source. The reflected and incident signal is measured using port 1; the output waveform is measured using port 2. Measurements can be made at one particular frequency or over a given range. For each generated frequency, the VNA measures the incident, reflected, and transmitted signal values ​​and calculates the parameter value. Each S-parameter contains the amplitude-frequency and phase-frequency characteristics (AFC and PFC, respectively) of the device under test in the corresponding direction.

If the applied network analyzer can only measure the amplitude, then it is called scalar . If an analyzer is capable of measuring both amplitude and phase, it is called a vector analyzer.

Most of today’s network analyzers are vector-based, because they allow the most complete measurement of the characteristics of the device under test in a given frequency range.

Using S-parameters, these analyzers can calculate and measure other parameters of RF devices. Network analyzers visualize the received data in different formats: amplitude in a logarithmic or linear scale, phase, group delay time, group delay, voltage standing wave ratio VSWR, real and imaginary parts, polar diagram, Wolpert-Smith diagram.

Network analyzer frequency expanders are designed to extend the operating range of standard low frequency VNAs to higher millimeter frequency ranges. These expanders provide users with an inexpensive alternative way to get their hands on a mmWave network analyzer without losing all the functionality and features found on industry standard models. Expanders of different structure with different number of ports are available for selection. Expanders are usually powered by external DC power supplies.

A typical VNA range extender contains (Figure 13) a scatterometer with two directional couplers and harmonic mixers to transfer the RF signal to the IF using the local oscillator signal.

Fig. 13. Generalized structure of the frequency expander of the vector network analyzer

In fact, the expander consists of a microwave transmitter, at the output of which couplers are installed one after another. In the transmission path, the expander contains an attenuator to control the signal level and reduce its unevenness in the operating frequency band. A receiver is connected to each of the couplers: one for sampling the outgoing signal for the reference (reference) mixer and one for the incoming/reflected (return) signal for the measurement mixer. Two VNA signals, one transmitter and one receiver, are shifted in frequency by a fixed amount to generate IF signals at a constant frequency and then measured by the VNA.

To obtain the most reliable results, correction of systematic measurement errors is necessary, for which the VNA uses a calibration procedure [3].

A fairly common solution used in HDRF to reduce the number of connecting cables used in a test setup, simplify and reduce its cost, is the transmission of different frequency signals over a common cable. In this case, duplexers and diplexers are used for their frequency separation.

Oleson Microwave Labs (OML)’s two-port harmonic mixer-based two-port harmonic mixers range extenders for use with spectrum analyzers that accept external mixers are an example of this solution. . These converters, which are based on millimeter-wave LO mixers, are connected to the input port of the spectrum analyzer, which allows you to extend the original operating range of the analyzers to 50-325 GHz.

Figure 14 shows the use and design of such a two-port 170-260 GHz WR04 extender with a harmonic mixer. To make measurements using existing test equipment, you must connect the DUT output to the waveguide input of an external mixer. The local oscillator signal is fed from the analyzer output (LO OUT) to the mixer in the expander. An external splitter diplexer provides communication between the heterodyne (LO) and IF (IF) ports of the spectrum analyzer over a common cable.

Fig. 14. The principle of use and design of two-port frequency converters based on harmonic converters WR04 (170-260 GHz) from OML

In fig. Figure 15 is an enlarged typical block diagram of a vector network analyzer that performs two-port S-parameter measurements in two directions at once. This design measures all the main four S-parameters without additional connection of the measured device in the opposite direction.

Fig. 15. VNA block diagram for two-port measurements of four S-parameters in two directions

The device under test is connected between ports 1 and 2. two ports. The analyzer typically uses two high quality, low error couplers, two measurement receivers, and one reference receiver.

Connected to a power divider or directional coupler, the reference receiver measures the incident reference (reference) signal. The incident signal through the port 1 connector is fed to the input of the device under test. The other port 1 receiver measures the signal reflected from the DUT input back to port 1. The transmitted signal through the DUT is sent to port 2, where the port 2 receiver is located to measure the transmitted signal. All measurements in the receivers are carried out synchronously on the signal of a common clock generator. In this way direct S-parameters are measured. To measure inverse S-parameters, the DUT is connected so that its input is connected to port 1 and its output is connected to port 2, which is carried out by a built-in switch.

Virginia Diodes (VDI) VNAs provide high quality network analyzer frequency extension in the terahertz range. The models cover the 50-1500 GHz range with additional bands under development.

Different test system configurations (Figure 16) can be used to interface and configure expanders with existing VNA test ports, depending on which S-parameters are being measured.

Fig. 16. Possible VNAX Expander Configurations

In addition to full transceiver modules (Transceiver, TxRx), VDI also offers Transmit-Reference (TxRef) and Receive only (Rx) modules, which provide optimized performance for specific applications and combine high test port signal strength with high dynamic range. They are compatible with most network analyzers and can be integrated into probe stations and antenna test chambers. When used with the PM5 power meter manufactured by this company, power level adjustment and scanning can be performed.

VDI offers two types of waveguide S-parameter calibration kits depending on operating frequency: TRL (Through-Reflect-Line) calibration for WR15‑WR3.4 waveguides and SOLT (Short-Open-Load-Through) calibration for waveguides types WR2.8…WR1.0.

Sage Millimeter manufactures 16 two-port and 14 three-port inexpensive network analyzer expander models. STN series scalar expanders provide full coverage of the waveguide range (Full Band) 26.5-170 GHz.

These expanders provide high performance test systems as they consist of high quality millimeter wave components previously developed by Sage Millimeter and have proven themselves (Figure 17). Such systems include STE series frequency expanders, STF series Faraday isolators, STA series programmable attenuators, SWD series directional couplers, and STD series waveguide detectors. Customers are offered different kit options to solve specific applications, differing in the combination of attenuator and coupler options. In addition, components with specifications different from catalog models are available upon request.

Fig. 17. Test System Using STN VNA Expanders and Sage Millimeter Components

Sage Millimeter currently offers three expander models for the STO series VNAs, the main parameters of which are shown in Table 5.

Expander models are developed by Sage Millimeter for full two-port S-parameter measurements from 60-110 GHz. They are compatible with current Rohde & Schwarz ZVA series and Keysight PNA-X series vector network analyzers. The dynamic range of frequency extenders can reach 100 dB. They are suitable for testing many microwave devices, including passive and active devices. A complete set of S-parameter measurements requires a pair of devices (Figure 18).

Fig. 18. Use of the STO-12203-S1 expander allows for two-port E-band measurements from 60-90 GHz

measuring RF systems, entered into a partnership agreement.

The CobaltFx Series is the first waveguide solution to use Copper Mountain Technologies VNAs up to 9or up to 20 GHz (Fig. 19). The large dynamic range and good directivity of the CobaltFx expanders allow high-precision and stable measurements of S-parameters in three waveguide bands: 50–75; 60-90 and 75-110 GHz. According to the manufacturer, the CobaltFx series products provide the best combination of price, performance, flexibility and size.

Fig. 19. Measuring system using CobaltFx series expanders of the Cobalt series network analyzer and with a connected controller

Used in the measurement system based on the Cobalt series, the C4209 vector analyzers are among the flagship products in the series offered by Copper Mountain Technologies. They provide high sweep speed (up to 10 µs per point) and a dynamic range of up to 160 dB. All these devices are implemented in a compact USB form factor. The C4209 analyzer works with Farran Technology’s FEV microwave frequency expanders (Figure 20).

Fig. 20. Microwave setup using Farran Technology’s FEV 9 expanders0003

Expanders are available in small, versatile cases with convenient port placement relative to the connected waveguides. Waveguide ports are manufactured in accordance with the new IEEE 1785
standard and are claimed to provide industry-leading path element frequency flatness (VSWR), repeatability of connections and results, allowing operation with long calibration intervals. The system comes with a Precision Calibration Kit that provides a full 12 parameter calibration of the device.

Farran Technology’s 10 frequency range extenders (Figure 21) for FEV-series VNAs provide highly accurate S-parameter measurements on 40-500 GHz mmWave products. Different measurement architectures are offered: 1-channel/2-port and fully reversing (reverse) two-port (reversing 2 port). Waveguide calibration kits are available as separate accessories.

Fig. 21. Farran Technology’s FEV

VNA Frequency Range Extender Models The extenders connect directly to the test ports of the VNA with or without an FEC controller. Using the network analyzer’s built-in capabilities, two- and four-port S-parameter measurements can be made. Measuring structures are proposed for network analyzers with one and two receivers of microwave signals.

Farran Technology’s Highest Frequency Model FEV‑2.2 VNA Expander with 10.86-16.67 GHz input frequency and 5-10 dBm input power; LO frequency: 11.61-17.85 GHz; extended operating frequency: 325-500 GHz; output power: -30 dBm.

Farran Technology FEK-15-0006, FEK-12-0006 and FEK-10-0006 Calibration Kits (Figure 22) provide accurate calibration of the WR-15, WR-12 and WR-10 mmWave measuring system, respectively . The kits provide two-port TRL (Thru/Thru, Reflect/Reflection, Line/Line) and full two-port SOLT (Short, Open, Load, Thru) calibration methods. Special waveguide calibration kits are also available to order.

Fig. 22. FEV (FEK) Series Calibration Kit

The FEC‑0x Series Frequency Extension Controllers are part of Farran Technology’s complete microwave measurement instrument solution (Figure 23). Their use ensures that the FEV-XX expanders are fully compatible with Keysight’s PNA-X Vector Network Analyzers and provide the best S-parameter measurement accuracy.

Fig. 23. Farran Technology FEC-02 Frequency Expansion System Controller

The three models of controllers currently offered have similar parameters. RF and LO input frequency ranges: 7-20 GHz; IF: 5-50 MHz; switching speed: less than 1 µs.

3J Microwave offers scalar network analyzer expanders and a complete line of EXTVNA frequency expanders for vector network analyzers in eight waveguide bands. The frequency expanders of the vector network analyzers of the series are characterized by low levels of harmonics and spurious signals. They provide compatibility
with the main models of vector network analyzers. Frequency expanders make it possible to measure circuit parameters at frequencies below 20 GHz up to eight 18-110 GHz millimeter wave bands (in K-… W-bands). Vector analyzer expanders can also be used in equipment bench test applications, for testing in antenna chambers and in instrumentation.

3J Microwave’s highest frequency extender, the EXTSNA-WR‑10, has an extension range of 75-110 GHz. The input frequencies from the VNA should be in the 5-40 GHz range. Expander Conversion Loss: -11 dB; dynamic range: more than 85 dB.

Table 6 lists the main features of 3J Microwave EXTSNA series scalar frequency spreaders. Supply voltage: +12 V.

24. Terahertz component test setup using VivaTech components

VivaTech offers 10 VNA expander models on the market (Fig. 24). The devices cover the frequency range 50-325 GHz in standard waveguide bands. The TR module provides wideband operation with high power output with low power ripple (Figure 25). The TR-TR configuration provides full two-port S-parameter measurement, the TR-R configuration allows cost-effective one-port S-parameter measurement or antenna testing (Tables 7-8).

Fig. 25. VivaTech dynamic range expanders for frequencies:
a) 75-110 GHz;
b) 110-170 GHz

OML’s popular VNA expanders allow technicians to make S-parameter measurements in the millimeter wave range. The DUT is connected using a standard waveguide flange that complies with MIL-DTL‑3922/67D (Figure 26). VNA modules implemented in waveguide bands operate in the frequency range of 50 GHz…0.5 THz and higher.

Fig. 26. OML VNA Frequency Expanders

OML Vector Network Analyzer Expanders are compatible with modern Keysight, Anritsu and Rohde & Schwarz VNAs. OML offers three module configurations for extending the operating range to mmWave: T/R, T, and S. Depending on which S-parameters are being measured, different system configurations can be used to interface and configure expanders with existing VNA test ports. tests shown in Fig. 27.

Fig. 27. Possible structures of test configurations using different expanders from OML

The most popular expander models from OML are the receive/transmit (T/R) modules and the T module, the structure of which is shown in fig. 28.

28. OML

Expander T Module Structures

For measurements, the waveguide test ports (WG test ports) of the expanders are connected to the device under test, while the RF, IF, and local oscillator (LO) inputs are connected to the test system controller or with VNA (VNA).

Figure 29 shows the structure of the most high-frequency expander WR-02.2 from OML, designed to test devices in the range of 325–500 GHz [4].

Fig. 29. OML’s WR-02.2 Expander Architecture and Frequency Plan

According to OML, the 325-500 GHz VNA expander implements the highest frequency that can be achieved with 20 GHz synthesizers. This expander provides the necessary suppression of subharmonic pollution of the spectrum of the generated signal. The use of such practical frequency multiplier structures to reach the next operating band above 500 GHz increases subharmonic pollution within the waveguide band to such an extent that unwanted spurious components cannot be filtered out to the desired levels.

Saluki manufactures five models of SAV364X Series Frequency Expanders (VNA S Parameter Test Module). S-parameter test modules are devices for extending the operating frequency range of high-end network analyzers to 50-325 GHz. These devices, together with vector network analyzers and controllers, allow you to build a system for measuring S-parameters in the millimeter wavelength range (Fig. 30).

Fig. 30. Saluki SAV364X Series Microwave S-Parameter Expanders and Using the Modules in a Controller Test System

A terahertz vector circuit test system can be built using the Saluki suite of S-parameter test modules SAV364X S, frequency extension controller SAV3640 and VNA (Figure 30). The system can be used in the manufacture, development, and testing of mmWave components, antennas, radar systems, and more. . Controller operating frequency range: 8-20 GHz; output power: 10 ±1 dBm. Controller supply voltage: 12 V at a current consumption of 2 A; dimensions: 426×177×460 mm.

Fig. 31. Saluki Technology’s SAV364X Series S-Parameter Test Controller and Frequency Expander

Rohde & Schwarz frequency expanders enable V, E, W, F, D, G millimeter-wave circuit analysis , J and Y at 50-500 GHz with R&S ZVA24/40/50/67 or ZVT20 network analyzers. Rohde & Schwarz’s ZVA-Z and ZCxx series transmitters (Figure 32) extend the operating frequency range to 500 GHz for network analysis. With a high dynamic range, these transducers allow measurements with very high reliability and high accuracy. The devices are easy to mount, easy to use and provide fast measurements.

Fig. 32. Rohde & Schwarz ZVA-Z110 and ZCxxx transmitter models

The ZVA Network Analyzer Expansion Unit (Figure 33) allows for complex measurements when testing devices such as signal amplifiers, for example. The unit is controlled directly using the ZVA GUI. Depending on the measurement task, the installation can be configured using combiners, harmonic filters, pulse modulators, a low noise preamplifier, or high power directional couplers (Fig. 34). The combination of the ZVA analyzer and the ZVAX24 block is a fully integrated single module. If several ZVAs are used for testing, they can share the expansion unit, which reduces the cost of the equipment.

Fig. 33. Frequency expansion unit ZVAX24

34. Block diagram of the ZVAX24 configurable extension unit

Rohde & Schwarz ZVAX-TRM configurable extension unit (Extension Unit) together with ZVA/ZVT network analyzers (ZVA24/40/50/67 and ZVT8/20) allows you to generate signals for conducting complex measurements of the parameters of microwave devices (Fig.