Voltmeter Tutorial

[gaillarry]

Anyone point me to a simple tutorial on how to use a digital voltmeter. I have the basic $20 meter. I know how to check for DC and AC voltage. Checking ohm readings is another matter. It has the amp socket but how to use it?

[Steve]

To measure ohms (resistance), you need to move the selector to one of the black positions between the 8 o'clock and 6 o'clock positions on the dial. The last two positions on the right are for diode check and...I'm not sure, maybe frequency. If you have an idea what approximate value you are looking for, put the selector in that range. For example, if you are checking your coil primary, you are expecting 3-5 ohms, so put it in the 20 ohm scale. If you are checking the coil secondaries, you are expecting 30-40k ohms (the k is 1000, so that's 30,000-40,000 ohms), so put the selector in the 200k position. There is no damage by using the wrong position. If you use a position that is too high, you simply won't get the precision you need. If you use a position that is too low, it will show OL or dashes or something to show it is out of range, simply move to the next higher position.

To use the AMP socket, move the red wire from the multi-function socket on the right to the AMP socket on the left. Move the selector to its matching position labelled 10A. Place the probes in series with the item you want to measure and read the display. For example, to check how much your headlight draws, connect the common terminal on the headlight (the left terminal) to the negative terminal on the battery with a jumper wire. Use the meter leads to connect the battery to the low beam (upper terminal) or high beam (right terminal) and read the current. Be aware that if you exceed the 10 amp rating, you wil blow a fuse inside the meter. The rest of the functions will likely still work, but not the 10A function. To measure lesser currents, keep the red lead in the right socket, use the 200mA position on the selector and check your load. You also have three more positions that will measure down to 200 micro-amps.

Next class: Meter Reading 102 8-[


By the way, that appears to be a decent basic meter. For those who are still shopping for a meter, consider spending a few extra dollars to get a meter that has auto-ranging. That way you only put the meter into OHMS function and it selects the range. Same with AC and DC volts.

.

[bakalorz]

To measure ohms (resistance), you need to move the selector to one of the black positions between the 8 o'clock and 6 o'clock positions on the dial. The last two positions on the right are for diode check and...I'm not sure, maybe frequency. If you have an idea what approximate value you are looking for, put the selector in that range. For example, if you are checking your coil primary, you are expecting 3-5 ohms, so put it in the 20 ohm scale. If you are checking the coil secondaries, you are expecting 30-40k ohms (the k is 1000, so that's 30,000-40,000 ohms), so put the selector in the 200k position. There is no damage by using the wrong position. If you use a position that is too high, you simply won't get the precision you need. If you use a position that is too low, it will show OL or dashes or something to show it is out of range, simply move to the next higher position.

To use the AMP socket, move the red wire from the multi-function socket on the right to the AMP socket on the left. Move the selector to its matching position labelled 10A. Place the probes in series with the item you want to measure and read the display. For example, to check how much your headlight draws, connect the common terminal on the headlight (the left terminal) to the negative terminal on the battery with a jumper wire. Use the meter leads to connect the battery to the low beam (upper terminal) or high beam (right terminal) and read the current. Be aware that if you exceed the 10 amp rating, you wil blow a fuse inside the meter. The rest of the functions will likely still work, but not the 10A function. To measure lesser currents, keep the red lead in the right socket, use the 200mA position on the selector and check your load. You also have three more positions that will measure down to 200 micro-amps.

Next class: Meter Reading 102 8-[


By the way, that appears to be a decent basic meter. For those who are still shopping for a meter, consider spending a few extra dollars to get a meter that has auto-ranging. That way you only put the meter into OHMS function and it selects the range. Same with AC and DC volts.

.

No ... no ... no

The part in red is probably not right.
Usually there is just a piece of wire in the meter for the 10 amp shunt, but no fuse.

All the other functions are usually protected, but not the 10 amp reading.
Be very VERY careful when you have a lead in the 10 amp socket, because your meter is now basically a direct short, and there is no overcurrent protection.

Also, if you have a lead in this socket, the meter is a short no matter what you have the dial set to.

So use the 10 amp socket when you need to, but take extra extra care whenever you have a lead plugged into it.

Oh, and by the way, the 10 amp setting will usually actually read up to 20 amps ... but do it quick, cause it will overheat the internal shunt in a couple of seconds ...

[gaillarry]

I bit the bullet and just bought an auto ranging meter for $38, with talking voice and audible warning beeps.

[Steve]

No ... no ... no

The part in red is probably not right.
Usually there is just a piece of wire in the meter for the 10 amp shunt, but no fuse.

All the other functions are usually protected, but not the 10 amp reading....

That would depend a LOT on the meter you are using. :shock:
Obviously I have not experienced the meters that you have, but all the Fluke meters that I have at home or have used at work are protected by two fuses. One is a 630mA fuse for most of the stuff, the other is a 10A fuse for the 10A setting. 8-[

Still good to be cautious, though.

.

[bakalorz]

That would depend a LOT on the meter you are using.
Obviously I have not experienced the meters that you have, but all the Fluke meters that I have at home or have used at work are protected by two fuses. One is a 630mA fuse for most of the stuff, the other is a 10A fuse for the 10A setting.

Still good to be cautious, though.

.

Fluke ... that would explain it ...

I've bought them from different sources, but always the cheaper ones.
None of them have had a second fuse.

I've shorted out power supplies, but never a lead acid or NiCad battery yet.
That might get exciting.\\/

When I was younger I saw someone get a steel "fishing snap swivel" across the terminals of a lead acid battery.
In about 2 seconds it glowed orange and melted into a puddle ...

Not sure what the OP's meter was, but if its cheap I'd be really careful.