True RMS. Two types of multimeters are available: average-responding and true RMS (root mean square). True RMS is measurement of AC voltage or current that reflects the amount of power dissipated by a resistive load driven by the equivalent DC value. An average-responding AC multimeter is calibrated to read the same as a true-RMS meter for sinewave inputs only. For other waveform shapes, an average-responding meter will give substantial errors.
Updating speed. General-purpose multimeters are available with display update rate of five per second. The higher the update rate, the better.
Battery life. A good battery life will make your life easier with electronics. Some advanced multimeters are quite power-hungry. Buy them only if you really require their advanced features. It is recommended to have a general-purpose multimeter with a battery life of 300 to 500 hours.
Measurement convenience
Below-mentioned features can make measurements very convenient, which means a lot while struggling with electronics circuits:
Auto range with manual override. In a manual-range multimeter you have to set the range before taking a measurement, which is very tedious. Go for an auto-range multimeter if you are serious about your electronics project. Ensure manual override function too as you will need it sometimes.
Automatic touch hold. This feature is very handy when both your hands are engaged in taking the measurement and you cannot look at the display for the reading. With this feature you can press the hold button and take measurement without looking at the display. The measured value will stay there until you reset it. Make sure that this feature is automatic, which means that you don’t have to press any button to freeze the reading because you will not have a spare hand to press the hold button.
Relative measurement. You can use this feature to analyse relative changes in the measured value. You can also use it to compensate for losses in the probes: Short both the probes and keep the relative measurement button pressed until it shows ‘0.’ This is very useful in resistance and voltage measurements.
Min/max mode. Hook up the multimeter to a circuit and use min/max mode to get the minimum and maximum of the values it recorded during this time period. This feature makes measurement of minimum and maximum values very easy as you don’t have to continuously look at the reading display.
Duty-cycle measurement. This is not really an essential feature in a multimeter as you will never measure the duty cycle of waveforms using a multimeter. There are other equipment for such measurements, such as an oscilloscope.
Display size, contrast and backlight. It is always better to go for a bigger display so that the readings can be read easily from a distance. Also, the display contrast should be high. Cheap Chinese multimeters have a very poor display contrast. Backlight is useful for taking measurements in dark.
Capacitance, temperature and frequency measurements. Capacitance measurement with a multimeter is not very accurate and you will need an LCR meter for that. However, a multimeter with capacitance measurement accuracy of up to 2 per cent is reasonably good. Temperature measurement is a highly useful feature that will reduce the number of test equipment from your table. Frequency measurement is not that useful but if you are getting it, look for the highest possible range.
Low-pass filter. Low-pass filter in a multimeter helps to block unwanted voltages above 1 kHz when measuring AC voltage or AC frequency. It can improve measurement performance on composite sine waves that are typically generated by inverters and variable-frequency motor drives.
Data logging. Data logging is very useful for a field job where you would want to log your measurements and recall them when you need. However, buy a multimeter with data logging facility only if you really need it because it will cause a big price difference.
Fast-response continuity latching. This is one of the features that you are going to use the most. Continuity testing is useful for tracing tracks, finding shorts and hundreds of other tasks. Fast-response continuity latching is a must for any multimeter. No datasheet mentions it but you need it as troubleshooting with a multimeter having slow-response continuity will be really annoying.
To assess a multimeter for fast response, set it in continuity mode and touch its probes to each other very quickly. Now do it faster and see the response. The tone should be solid and appear every time you touch the probes.
With fast-response continuity function you can find shorts on a chip just by wiping the probe across the pins, which is impossible with slow-response continuity multimeters.
