A digital multimeter (also known as a digital multimeter) is a multifunctional electronic measuring instrument that is widely used in the measurement of parameters such as voltage, current, and resistance. The following is a detailed description of the detection methods of digital multimeters and electronic measuring instruments:

Detection methods of digital multimeters (digital multimeters)
Voltage measurement
DC voltage measurement: Turn the rotary switch to the "DCV" position and select the appropriate range. Insert the red test lead into the "VΩ" socket and the black test lead into the "COM" socket. Touch the positive and negative poles of the circuit, and read the voltage value on the display to get the actual voltage.
AC voltage measurement: Turn the rotary switch to the "ACV" position, with the AC symbol "～". Touch the test leads to the two ends of the circuit respectively, and read the voltage value on the display to get the actual voltage.
Current measurement
DC measurement: Turn the rotary switch to the "DCA" position and select the appropriate range. Connect the test leads in series to the circuit as needed, paying attention to the polarity.
AC measurement: Turn the rotary switch to the "ACA" position, and the operation method is similar to DC measurement.
Resistance measurement
Switch the rotary switch to the "Ω" position, insert the red test lead into the "VΩ" jack, and the black test lead into the "COM" jack. Touch the two ends of the resistor to be measured and read the resistance value on the display. Note that the circuit should be powered off before measuring the resistance.
Capacitance measurement
Some digital multimeters have the function of capacitance measurement. Switch the rotary switch to the capacitance position (usually marked as "C"), connect the pins of the capacitor to the test lead, and read the capacitance value.
Diode measurement
Switch the rotary switch to the diode position (usually marked as "D"), connect the diode, and there should be a conduction display when connected in the forward direction.
Continuity test
Under the continuity test position (usually with a beep sign), you can check the conductivity of the circuit.
Range selection
Before measuring, confirm whether the measurement range is appropriate to avoid damaging the multimeter.
Testing methods for electronic measuring instruments
The testing methods for electronic measuring instruments vary depending on the type of instrument and the measurement parameters, but usually include the following steps:

Appearance inspection: Check whether the appearance of the instrument is intact and whether there is any damage or deformation.
Functional check: Check whether the various functions of the instrument are normal according to the instrument manual or operation manual.
Precision calibration: Use a standard source or calibration equipment to calibrate the instrument to ensure the accuracy of the measurement results.
Signal input and output check: For instruments with signal input and output functions, check whether their input and output signals are normal.
Stability check: Observe whether the measured value of the instrument is stable over a period of time to evaluate its stability performance.
In addition, for different types of electronic measuring instruments, further tests can be performed according to their specific measurement parameters and characteristics. For example, for an oscilloscope, you can check whether its waveform display is clear and accurate; for a spectrum analyzer, you can check whether its spectrum display is complete and accurate, etc.
When testing electronic measuring instruments, you should strictly abide by the operating procedures and safety regulations to ensure personal safety and the integrity of the instruments and equipment. At the same time, the instrument should be regularly maintained and serviced to extend its service life and maintain its measurement accuracy.