subject: How To Use Digital Oscilloscopes To Measure Special Signals part Two [print this page] In the last article, I have introduced two ways of special use for digital storage oscilloscope. Now, I will introduce other two ways of measuring special signals.
3. Test the jitters in periodic signal
Some high-end digital storage oscilloscopes have a specialize software which is for testing jitter, so they can use this function go with comprehensive jitter measurements.However, the digital storage oscilloscope which has no jitter software only through the infinite persistence to test signals for cumulative time. In addition, we can use cursors to measure the jitter from peak to peak, so that the measurement results will be more reliable. For example, the following steps to set the measurement for a common one:
(1) Press the CURSOR button;
(2) Press the Function button in the screen;
(3) Select V Bars cursors;
(4) Press Bring Both Cursors On Screen button to quickly locate the screen cursor;
(5) Place a cursor in the edge of the first down, and place another cursor in the edge of the last down.
(6) Read jitter time from the peak to peak
4. Capture real signals by correct using the probe
The people who is design or test in any measurement, always needs the realistic signals by the oscilloscope. Application of the digital oscilloscopes should not affect the signal itself in any way, but almost any test will has an impact on the signal. It is very important by using probe correctly, so the probe can make the signal more realistic. When you connect a probe to any input channel first, it should compensate the probe till the oscilloscope has input. It can come true a best measurement as the probe and input channel have matched. When you use the probes which are random match with the digital oscilloscope should not to set the impedance to 50, because the impedance of probe in parallel with the one of input will cause the impedance of test circuit input less than 50, so test the high resistance of the electrical signal will lead to a false appearance which is can not capture any signals.
In addition, probe in a common digital oscilloscope has a ground wire. With the measured points form a loop antenna similar to the path interference, it will lead to a relatively large interference. The way to reduce the interference is to remove the cap of the probe, and not to use the ground wire which is connected the probe but directly use the tip and internal of the probe to test.
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