How To Measure Gain On An Oscilloscope (2024)
Oscilloscopes are essential tools for engineers to observe changes in voltage in electrical signals.
They are among the most important devices engineers use, especially when it comes to measuring gain.
In this blog post, we’ll explain how oscilloscopes measure gain and offer tips on how to use your oscilloscope for this purpose.
If you want to know more about oscilloscopes and their functions, check out our blog post comparing signal analyzers and oscilloscopes.
What Is Gain?
Gain refers to how much an amplifier increases the strength of a signal. It’s usually shown as a ratio of the input to output voltage or current and is sometimes called amplification.
For example, if an amplifier’s output voltage is 1 V and the input voltage is 0.5 V, the gain is 2 because the amplifier doubled the voltage.
In simple terms, the gain is how much the signal is boosted. Understanding gain is crucial in electronics because it affects how much an amplifier changes the input signal.
For instance, if you have a 0.5 V signal and use an amplifier with a gain of 2, the output will be 1 V, which is the desired result.
However, if you start with a 1 V signal, the output will be 2 V. If a signal is amplified too much, it can lead to issues like distortion and noise.
How Do Oscilloscopes Measure Gain?
Before we talk about measuring gain with an oscilloscope, it’s important to know how the oscilloscope does it. You can measure gain in two ways: manually or automatically.
Manual Gain Measurement
With manual gain measurement, you manually set the gain (or amplification) of the amplifier, and then use the oscilloscope to measure the voltage drop across an input capacitor.
This method can be useful in certain cases, but it’s generally not recommended because it can be inaccurate.
Manual gain measurement is a fast way to check gain and can be handy for quick comparisons between signals.
However, it’s not ideal for regular use due to its lack of accuracy.
Automatic Gain Measurement
Automatic gain measurement is more accurate. It involves sending a known voltage signal through the amplifier and using the oscilloscope to measure the output voltage.
Keep in mind that automatic gain measurement isn’t instant—it takes a few milliseconds. So, when you measure gain this way, you need to run the signal for a few milliseconds and then measure the output with the oscilloscope.
Automatic gain measurement is a reliable and precise method, and it’s recommended for regular use.
Tips On How To Measure Gain With An Oscilloscope
A. When measuring gain with an oscilloscope, it’s important to use a clear signal. If the signal has too much noise, the oscilloscope may not accurately measure the amplifier’s gain. If you’re struggling to get a clear signal, you can use a signal source to generate one or try lowering the amplifier’s gain to reduce the noise.
B. The oscilloscope’s scale affects how gain is measured, so it’s crucial to set the oscilloscope to the right scale. If you’re measuring AC voltage, the oscilloscope should be set to AC volts. For DC voltage, set it to DC volts. Also, choose the right range. For example, if you’re measuring voltage between 0 and 10 V, set the scale to 10 V.
C. Different amplifiers are made for different purposes, so it’s important to use the right one for your application. If you’re measuring gain in a low-level application, use a low-level amplifier. For a high-level application, use a high-level amplifier.
Limitations Of Oscilloscope Based Measurement Of Gain
Oscilloscopes are useful tools, but they have some limits when it comes to measuring gain.
A. Measuring gain manually is not very accurate. It’s better to use automatic gain measurement with an oscilloscope because it’s more precise.
However, automatic gain measurement takes time, so if you need quick results, an oscilloscope might not be the best choice.
B. Oscilloscopes also have limited bandwidth, which means they might not measure high-frequency signals accurately. To get better results, you should use a low-frequency signal, like something between 50 Hz and 500 Hz when measuring gain.
C. It’s important to set up the oscilloscope correctly for measuring gain. If you’re measuring AC gain, use an AC coupling capacitor, and if you’re measuring DC gain, use a DC coupling capacitor. Also, make sure to adjust the trigger type and level, vertical and horizontal sensitivity, and the time base correctly.
Final Thoughts
Gain is an important measurement when working with any kind of amplifier. You can use an oscilloscope to measure gain, but there are some limitations to keep in mind.
To get accurate results, it’s crucial to use a clean signal, adjust the scale correctly, choose the right amplifier, and set up the oscilloscope properly.