What is the difference between an oscilloscope and a multimeter?
Oscilloscopes and multimeters are essential equipment for daily development and debugging of electronic engineers. The multimeter is mainly used to test the voltage/current value at a certain time point, etc., and the oscilloscope is used to draw the waveform of voltage/current changing with time. Do you know how to apply the two correctly?
Measured selection
So how to judge under what test conditions to choose an oscilloscope or a multimeter to measure? Taking the capacitor charging and discharging process as an example, the schematic diagram is shown in Figure 1. Use a 5V DC power supply to power the system. When S1 is closed, the capacitor is in a charging state; when S1 is disconnected, the capacitor is in a discharging state. Ideally, Figure 2 is the analysis of the charge and discharge waveforms, where Ta is the time required for the capacitor to charge and Tb is the time required for the capacitor to discharge.
The multimeter (DMM6000) and oscilloscope (ZDS4054 Plus) of Zhiyuan Electronics were used during the test. According to the official indicators, the accuracy of the multimeter (DMM6000) is 0.0035% of reading + 0.0007% of the range, and the accuracy of the oscilloscope (ZDS4054 Plus) is 2% of the full scale.
From the perspective of accuracy, the accuracy of the multimeter is obviously better. Connect the oscilloscope probe or the red and black test leads of the multimeter to both ends of the capacitor to test the voltage when the capacitor is fully charged. The voltage measured by the multimeter is 2.60922V, and the voltage measured by the oscilloscope is 2.68000V (because the DC power supply is connected, the peak-to-peak value of the voltage = the effective value of the voltage). The accuracy of the multimeter (DMM6000) is 0.0035% of the reading + 0.0007% of the range, that is, the error range is ±0.0001613V; the accuracy of the oscilloscope (ZDS4054 Plus) is 2% of the full scale, that is, the error range is ±0 ．1600000V.
If you need to observe the waveform of voltage changing with time or measure the time required for charging/discharging to complete, you should choose an oscilloscope. From the perspective of the time dimension, the oscilloscope can intuitively observe the process of capacitor charging and discharging, and can measure the time required for capacitor charging/discharging to complete through the cursor or [Measure] function. As shown in Figure 5, the rise time (ie, the time required to complete the capacitor charging) is 9.4307s and the fall time (ie, the time required to complete the capacitor discharge) is 9.6295s through automatic measurement.
Assuming that a multimeter is used for measurement, the changing voltage value can only be measured and recorded manually at intervals, and finally the waveform diagram is drawn manually. From the rise time measured by the oscilloscope, the duration is very short. Although one data is manually recorded per second, the rise time can only record up to 9 data, and the voltage change restored by these 9 data is of no reference significance. Compared with the multimeter, the current sampling rate of the oscilloscope is 2MSa/s (2,000,000 sampling points can be collected per second), which not only has a higher degree of restoration, but also is more convenient, which can save a lot of time and manpower.
