basic skills
The measurement of current, voltage and resistance is generally regarded as the basic function of a multimeter. The brand of the early multimeter manufacturer A.V.Ω is the abbreviation of the names of the three units of measurement that the device can measure: A Ampere, V Volt, Ω Ohm (Ohm), so early electricians generally still The multimeter is called a three-meter.
New devices have been developed that can measure many more metrics; some common additional features, and the units of measure they measure, include:
H Inductance (Henry)
F capacitor (farads)
Conductance (Siemen) ---- Rarely used
°C/°F Temperature (Celsius or Fahrenheit)
Hz frequency (Hertz)
% duty cycle (percentage)
DWELL closed angle (car digital multimeter)
TACH Tach (RPM, Automotive DMM)
hFE (transistor magnification)
Functional Auxiliary Symbols or Logos:
AC or ~ , AC
DC or = , DC
Commonly used forms such as: DCV (direct current voltage), A~ (alternating current)
Advanced Features
From control circuits to small embedded computers, integrated circuits enable modern digital instruments to provide more functionality.
Common enhancement measures include:
Current-limiting semiconductor junction voltage drop measurement, used to determine the type of transistor;
Graphical display of measured quantities, such as histograms;
Can make go/no-go measurement easier;
Continuous measurement, and sound alarm when the circuit occurs;
low frequency oscilloscope;
telephone test device;
Automatic circuit testing, including automatic timing, delay signals, etc.;
Simple data detection functions, such as recording maximum and minimum readings for a specified period, or taking a certain number of sample readings at regular intervals
Sample and hold to lock the last reading for reading after the device is removed from the test circuit;
The test range is automatically converted, and the meter automatically selects the appropriate measurement range during measurement to protect the meter from damage.
Digital multimeters usually have circuitry or software that can ensure accurate measurement of AC voltage at any frequency. This type of multimeter uses the rms method to combine the input signal, so that even if the input signal is not an ideal sine wave, it can correctly read the true voltage value.
Some modern multimeters can be connected to a personal computer via infrared, RS-232 or IEEE-488 device bus, etc. In these ways, the computer can record readings while taking measurements, or upload a set of results from the device to the computer.
Modern equipment and systems are becoming more complex, and the multimeter is becoming less common in the technician's toolbox; more complex and specialized equipment is replacing it. For example, when measuring an antenna, a worker might have used an ohmmeter to measure its resistance; a modern technician might use a handheld analyzer to test several parameters to determine the integrity of the antenna cable.
