As an "old acquaintance" in the field of electronic engineering, oscilloscopes have always been favored by engineers. Everyone has a unique opinion on how to use it. So how do you use an oscilloscope more efficiently? Based on this problem, let's go deep into the ** together. This article summarizes some of the basic concepts of an oscilloscope and how to use an oscilloscope to make basic measurements.
An oscilloscope is an electronic measuring device that displays a plot of voltage over time. This allows the user to observe the change of voltage and time at the same time. Most oscilloscopes are capable of displaying multiple voltage signals on their screen, and this feature gives us the ability to compare the behavior of these signals. ”
DigiKey oscilloscope].
As can be seen from the graph above, we can see two observations:
The peak-to-peak voltage of the waveform can be measured along the longitudinal axis. It is the five main partitions, and the vertical gain is set to the 200mV partition (yellow arrows can be seen here), which shows the signal amplitude of 1 volt peak-to-peak.
The horizontal axis is the time, and the range is set to divide by 200 s (see the white arrow here). A period of a sine wave spans five major parts, so the period is 1 millisecond, which means that the frequency is 1 kilohertz. (This particular oscilloscope has a counter that shows the frequency of the signal in the upper right corner.) )
Measure voltage, voltage difference, and time interval.
Measure the frequency of repetitive signals.
Compare two or more signals over time and find the relationship between them (e.g., whether a particular feature on one waveform appears before or after a feature on another waveform).
Capture special behaviors such as transients, faults, etc.
Measure the DC and AC portions of the waveform.
Measure various characteristics of the waveform, such as peak-to-peak voltage, rms voltage, period, rise time, fall time, etc.
Check for noise on the signal and modify how the circuit or cable changes the signal noise.
Find distortions in circuits by visually comparing input and output waveforms—or use an oscilloscope to subtract them while seeing mathematical differences.
The meaning of the symbol
Signal vs. Waveform: According to an oscilloscope, the word "signal" refers to a voltage that can change over time. The difference is whether the signal can be periodic. Periodicity means that the signal repeatedly takes the same set of values at different intervals. A sine wave is an example of a periodic waveform. Its characteristics are as follows:
Sine wave].
Non-sinusoidal waveform].
The letters shown in the image above represent the following meanings:
a - square wave.
b - pulsed waves.
c - triangular wave.
d - oblique wave (also called sawtooth wave).
e - rectified sine wave.
f - square root wave (the amplitude is proportional to the square root of the start time of the wave period).
Screen grids: The most primitive measurement technique is to use the grid lines on the screen and calculate the number of grids.
Examples:
Teledyne's HDO4104A].
The diagram below shows a sine wave with five periods:
The sine wave trajectory covers six blocks vertically, multiplied by a vertical scale factor of 50 millivolts (mv) per cell (i.e., the channel 1 descriptor box) to calculate a sine wave amplitude of 300 mV (peak-to-peak). Similarly, the period of the sine wave covers two horizontal grids, and each grid in the timebase descriptor box is 100 nanoseconds (ns), so the period is 200 ns.
The method of calculating the number of lattices may seem primitive, but it is a very quick way to make basic measurements.
There are many types of probes, including: high-impedance passive, low-capacitance, single-ended active, differential active, high voltage, and current probes. Among them, passive probes are very common.
The actual measured signal, which can be very large, will exceed the oscilloscope's input threshold. A probe with an attenuator, such as the common 10x probe, should be used to attenuate the input signal by a factor of 10.
Digilent's 460-004 oscilloscope probe 1x 100x].
There is also a 1x 10x probe that is popular because they include a switch in the probe body that allows the user to switch back and forth between the 1x position, the 10x position and the position where the input wire is connected to the ground wire. But the downside of a 1x 10x probe is that it will likely be left in the 1x position unexpectedly in the event that you need it to be in the 1x position. This results in qualitative and quantitative measurement errors, as the attenuation is not expected in the assay and the frequency response is very different from the frequency response at the 10x position.
Oscilloscopes typically provide 50 or 1 m input ports. The 50 port is typically paired with a matching coaxial cable to connect to a circuit element with a 50 current source.
The source impedance is higher when a 1m input termination is used to connect the circuit. This connection can be done in a variety of ways, including using either the cable directly or the X1 probe, or using a high impedance probe.
Set the switch on the probe to 1x and connect the probe to channel 1 on the oscilloscope. This point requires attention to aligning the slots in the probe connector with the keys on the CH1BNC, pushing the connection while twisting to the right to make it easier for the probe to lock in place. Connect the probe tip to the reference wire to the Probe Comp connector.
Edit the search image.
High-impedance probes utilize a low-frequency compensation process that matches the channel they are connected to. For this process, all oscilloscopes provide a low frequency square wave, typically 1 kHz, which is commonly referred to here as a CAL output. To take advantage of this feature, first connect the probe to the desired channel and then connect the probe tip to the CAL output. Trigger the oscilloscope and view the selected channel trajectory on the screen. Using the adjustment tool, change the compensation adjustment in the probe connector box to obtain the square angle on the square wave trajectory, as shown in the middle trajectory
Whenever the probe is connected to a different channel, it should be compensated, especially before any critical measurements. Most high-impedance probes also offer high-frequency compensation adjustment. Such adjustments are generally not required. The probe manual provides detailed information on this test.
The oscilloscope displays voltage versus time while testing the displayed waveform. Use of different measurement techniques such as scales, cursors and automatic measurement modes. B&K's 2190e is used as an example
This mode will take effect when the measurement is automated. The instrument will display a cursor when the parameters are automatically measured. These cursors show the physical significance of these measurements. To perform an automatic cursor measurement, you should follow these steps:
Press the cursor key to enter the "Cursor Measurement Menu".
Press the Cursor Mode radio button to select Automatic.
Press the "measure" key to enter the "Auto Cursor Measurement Mode Menu" and select the parameters to be measured.
In the case of automatic measurements, the oscilloscope helps the user to complete all the calculations. Measurements are made using all the points recorded in memory, which is more accurate than using raster lines or cursors, as these measurements are limited to using the points on the display, not all the data points recorded by the oscilloscope.
Press the "measure" key to automatically test.
There are three types of automatic measurements: voltage measurement, time measurement, and delay measurement. There are a total of 32 measurement parameters.
Suppose you want to measure the voltage parameters, you can follow the steps described below:
Press the "measure" key to enter the "Automatic Measurement" menu.
Press the first radio key to enter the "Secondary Measurement" menu.
Select the measurement type. Suppose you press the "Voltage" radio button, and the "Voltage Measurement" menu will appear on the screen.
Press the radio button of "Source", and select "CH1" and "CH2" according to the input signal channel.
Press the Type radio button to select the type of parameter you want to measure. Icons and values are displayed below the measurement parameters.
Measure VPP parameters].
Press the "Back" radio key to return to the "Auto Measurement" menu home page. The selected parameters and corresponding values will be displayed at the top of the homepage.
In the same way, the user can display other parameters and their values in the corresponding places. The screen is capable of displaying 5 parameters at the same time.
If you want to measure time parameters using all measurement functions, you can do so by following the steps below:
Press the "measure" key to enter the "Automatic Measurement" menu.
Press the radio button at the top to enter the second page of the "Automatic Measurement Menu".
Press the "All Measure" radio button to enter the "All Measure Menu". Press the Source radio button to select the input signal channel.
Press the "Time" radio button to select "On". All the time parameter values are now displayed on the screen together, as shown in the image below
Measure all time parameters].
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