Hello,
I have some questions regarding the measurement of voltage using a digital multimeter.
1. What will happen if I want to measure a DC voltage but my multimeter is set to Resistance ?
Although good quality multimeters have protection to guard against damage if you do this, you should try really hard to avoid doing it. Try to cultivate good habits, for example always check the range setting before connecting probes to a device under test, always detach the probes when you have finished a measurement, and never turn the meter selection dial while the probes are attached to a device.
I'll say the same as two gents above. While especially new / modern multimeters are tried to be made safe for all ranges, you still should try to learn the "proper measuring procedures".
That is (at top of my head and not in strict order of importance):
- clean working environment, no clutter.
- Read the fucking manual.
- Identify the DUT and go it through with though to determinate what kind of energy levels you are facing (high currents, high voltages, high frequencies etc.)
- Rule of thumb is that every 1000 volts can jump 1 mm through air, so 10'000 V will jump 10 millimeters.
- All unnecessary cables and wires attached and non insulated ends ended ie. with some terminal strip.
- All unnecessary circuit separated from power (especially with mains or high voltages )
- All capacitors should be threaten as potentially lethal and should be shorted with small resistor before measuring, bleeders might be malfunctioning.
- In slightest doubt use only off-line measurement methods (turn power off and attach the measuring device and then turn power on).
- Active control circuitry should be stopped and locked in the safe state (both hardware and software based)
- Double check your meter is in safest mode available (typically highest voltage range) and your test circuit is connected as should (test leads in voltage ports not in current etc.)
- Verify your measuring device is working correctly from known source.
- Start with verifying the voltage in the circuit both in AC and in DC starting with the highest range in the measuring device
- In case of current measurement, be absolutely sure that you have right side of load in series with your meter. The load is only thing that will prevent a short circuit at it should be connected in any circumstance series with your meter (meter in current measuring mode is same as bare wire between measuring points).
- The old mantra of electricians "keep one of your hand at back pocket" is still relevant while working with (*unknown) live circuitry.
*unknown - a circuit which voltage, current or general peak energy levels are unknown or a known circuit that is behaving abnormal way or a prototype of some form without a known separation from high energy circuitry.