The measurement value drifts due to changes in the position of the current probe lead. How to ensure measurement accuracy?
When measuring large currents, use a flexible current probe or Rogowski current probe. Its current loop is relatively large, and a slight movement of the passing wire will affect the measured value. In this case, it is recommended to fix the current flowing through the wire in the middle of the current loop. If you want to reduce the error caused by position, you can use a current probe with a small current loop diameter. It is recommended to use a multimeter or picoammeter to measure small currents.
Can ordinary passive high-impedance probes measure mains power?
The mains power waveform is a 220Vrms sine wave, which can be measured with a passive high-impedance probe at 10X level. Its maximum input voltage is generally 300Vrms, which is greater than the mains rms voltage.
However, please note that the CAT II level of the 1X level of the passive probe is only 150Vrms, which means that the maximum voltage allowed in the environment used on an indoor socket can only be 150Vrms, which does not meet the withstand voltage limit of 220Vrms for measuring the mains power. Although the 1X level The voltage fed into the oscilloscope at 1X position is 220Vrms. Using the 1X position to directly measure the mains power will damage the probe.
If you use a coaxial wire to directly introduce mains power into the oscilloscope, although this will avoid damage to the 1X probe, it can be seen from the maximum input voltage indicator of the oscilloscope that the safety level is reduced to CAT I level at this time, and in principle it is not suitable for testing in the laboratory. Such measurements. Therefore, it is recommended to use a high-voltage probe to measure mains power, which is relatively safe.
I only have an ordinary oscilloscope at hand. How can I measure floating signals?
The principle of floating signal testing is to ensure that the signal is not short-circuited to ground. If you have a non-floating oscilloscope or a battery-powered oscilloscope, you can use a differential probe to perform floating measurements. The test is safe and direct and has good common mode rejection (similar power frequency interference). For simple measurements, you can connect a single-ended probe to the two channels of the oscilloscope, use the positive terminal of the probe to measure both ends of the floating signal, and the alligator clips of both probes are grounded. Then use the internal channel operation function CH1-CH2 of the oscilloscope to obtain the potential difference waveform of the floating signal.
Does any probe require probe compensation?
Probe compensation is mainly for necessary measurement preparations for internal impedance matching of passive probes. Probe compensation is performed by rotating the reserved capacitance knob Ccomp to eliminate distortion and ensure accurate measurement, such as passive high-impedance probes, passive high-voltage probes, etc. General active probes require internal zeroing and calibration to achieve accurate measurements, such as differential probes and current probes.
