How to Evaluate Oscilloscope Noise for Low-Level Measurements



Although the oscilloscope is a very useful device, it has some disadvantages. One of these disadvantages is the noise experienced in the oscilloscope measurement system. Noises experienced especially in low level measurements cause the sensitivity of the measurement to decrease. So, what does oscilloscope measure? How does the oscilloscope measurement? How does the oscilloscope work? How does oscilloscope noise occur at low level measurements? Let's examine together.

What does an oscilloscope measure? 

The oscilloscope can basically be described as a graphical imaging device. Devices that measure the current electrical signals by classifying them according to time and amplitude on their screen are called an oscilloscope. The oscilloscope basically measures two things. 

  • Voltage
  • Time


Oscilloscopes are primarily set up to measure the voltage of an electrical signal. These voltages are then presented graphically in waveforms. Apart from voltage, the oscilloscope can also measure time values. Especially in digital oscilloscopes, oscilloscope measurement proceeds much more comprehensively and effectively. Frequency reading is also done while measuring the voltage. It is very easy to reach such factors as the frequency of the signal tried to examine, the standard deviation ratio and average frequency values. While certain frequency adjustments must be made to make oscilloscope measurement in analog oscilloscopes, there is no such situation in digital oscilloscopes. The values ​​that the oscilloscope can measure in more detail are as follows.

  • AC ve DC voltage values measurements
  • Time measurements
  • Phase difference measurements
  • Circuit frequency measurements
  • Current measurements passing through the circuit
  • Waveform measurements of variable electrical quantities
  • Pulse width and rise time measurements


How to use an oscilloscope?

Although the oscilloscope is divided into 4 different types, the working practice is basically the same. The oscilloscope is a test equipment item that can be used for testing and troubleshooting various electronic circuits, from analog circuits to radio circuits, from radio circuits to electronic devices. To be able to use it in the best way, it is necessary to know how to use an oscilloscope correctly. Knowing the basics of using an oscilloscope helps to better analyze signals, find errors more quickly, and use the oscilloscope in a much more useful way.

While oscilloscopes are more expensive than some other testing equipment, including multimeters, they are often found in electronics enthusiasts' homes and workshops. As a result, it is very important to know how to use an oscilloscope. The first step of using the oscilloscope is to make some adjustments. These steps are; vertical gain is vertical position, time base, trigger, trigger holding and beam detection. After these adjustments, the power of the oscilloscope must be opened. In this way, the oscilloscope screen becomes visible. The horizontal gain control needs to be adjusted when forms begin to appear.

After adjusting the waveforms, the speed of the time base should be adjusted. The necessary image will be obtained with the application of the signal and the trigger. The last step is to carry out the controls to reach the best according to the signal captured. As a result, using an oscilloscope is not as difficult as it is thought. It has many advantages in the oscilloscope, but in some cases it can occur in undesirable situations. One of them is the noise level.




How to Evaluate Oscilloscope Noise for Low-Level Measurements?

Oscilloscopes can cause noise, especially at low level measurements. These noises can cause amplitude measurement errors, cause waveform uncertainty, visually generate undesired waveforms, or detect input signals incorrectly. This is actually a matter of considerable attention, as it leads to complete misunderstanding of the signals. Extra care must be taken to reduce oscilloscope measurement noise, especially if the observed signal is small.

There are two types of noise occurring in oscilloscopes. These; 

  • Constant noise from the front end of the oscilloscope
  • Lower noise due to the dynamic range of the oscilloscope

The most known noise specified in the oscilloscope data is the noise from the base and related to the vertical scale settings. There are a few things that can be done to solve this situation. The first is to adjust the bandwidth. It can be determined how noise is affected in different bandwidths. While increasing bandwidth in general is beneficial for oscilloscope measurement, it can increase noise.

Therefore, it would be reasonable to limit bandwidth. In addition, using the oscilloscope as a 1: 1 probe can help reduce noise. It is better to use differential active probes for oscilloscope measurement using wider band gaps. In order to obtain the results of the signal in a better way, the oscilloscope measurement system noise can be recovered and the square root formula of the sum of squares can be used.

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