How To Use A Multimeter To Test

That is a prize, Bill. Most folks don't even remember who Heathkit was, much less any of their products.
 
Ok so most of the typical multimeters I have seen cannot measure power in one step but they can with two and some math. Power is measured in watts usually. But if that picture is your multimeter it cannot measure amperage which is one of the measurements you would need. If you just need voltage you can measure from neutral to hot for ac or pos to neg for Dc. Amperage has a little ditty I was taught called make a brake fill a brake. So you make a brake in the circuit then insert one probe on each side so the multimeter fills the brake. Note my fluke multimeters only go up to ten amps and more will blow the fuse. Anything more I usually have to use one of the bigger power meters.

Then wattage is simply amps times volts

P=V*I

Now this is simplified and not technically correct for ac but it will get you in the ballpark. If you need more precise than that I don't think you would be asking how to measure power.
 
You're correct that most of the older analog VOM's and VTVM's do not measure AC amps (or power). But VOM is an abbreviation for Volt-Ohm-Milliammeter, although a few do go up to 10 amperes DC. But for measuring current in an AC circuit (saying or writing "AC Current" always bothered me), Simpson and a few other manufacturers made a clamp-on accessory that when plugged into a 260 in place of the normal leads, added that capability. And had the advantage over the standard clamp-on AC ammeter that the meter or indicator didn't have to be dangling on the wire that you were measuring. They also made a line splitter adapter widget that plugged into a wall outlet or extension cord. Then the device under test was plugged into the widget and the clamp-on accessory had individual access to either the line or the neutral going to the load.
 
terrywerm said:
That is a prize, Bill. Most folks don't even remember who Heathkit was, much less any of their products.
Click to expand...

I have a nice old Heathkit meter that I built back in the 70's. Only problem is it takes an 8.4V mercury battery that's no longer made. One of these days I'll rework it for a 9V battery and a voltage regulator.
 
FanMan said:
I have a nice old Heathkit meter that I built back in the 70's. Only problem is it takes an 8.4V mercury battery that's no longer made. One of these days I'll rework it for a 9V battery and a voltage regulator.
Click to expand...

Put in a nickel cadmium rechargeable, they're 8.2 at full charge, close enough - or put a diode with its 0.6v drop in series?

Dave H. (the other one)
 
British Steel said:
Put in a nickel cadmium rechargeable, they're 8.2 at full charge, close enough - or put a diode with its 0.6v drop in series?

Dave H. (the other one)
Click to expand...

The issue is the voltage drop as the battery discharges, whIch makes the zero drift. Mercury batteries were very constant voltage. I can actually use a 9V dry battery, but I'm constantly adjusting the zero.
 
My Heathkit does not suffer from that battery problem. It has a cord sticking out of the back with a "thingy" on the end with two metal prongs that fit the socket on the wall. Devil made me say it, ROTFLMBO.

"Billy G"
 
FanMan said:
I have a nice old Heathkit meter that I built back in the 70's. Only problem is it takes an 8.4V mercury battery that's no longer made. One of these days I'll rework it for a 9V battery and a voltage regulator.
Click to expand...

You might try it without a voltage regulator. I have an old Simpson 260 that had the 15 volt battery that probably is no longer available.
I put two nine volt batteries in series( 18volts) and it worked out just fine. The variable rheostat that sets the peak needle reading compensated
for the increased voltage of the two nine volt batteries.

EDIT: Oops! I see you already tried that. I usually set my needle before use anyway.
 
Is it the ohmmeter zero that must be readjusted over time, or the actual meter zero? If the former, most multimeters have to have the ohmmeter zero set as you switch from Ohms range to range anyway. If the unit has an ON/OFF switch that can be wired to disconnect the battery when OFF, then you could use a simple shunt regulator.
 
It's been awhile since I looked at it, but as I recall there are two adjustments on the front, one for zero and one for ohms. Internally there is a "bias" adjustment to compensate for battery voltage. The meter manual says you can use a 9V battery in an emergency but there will be excessive drift that has to be compensated with the bias adjustment when you run out of front panel zero adjustment, a PITA. A regulated power supply would solve this. The meter actually has two batteries; there is also a 1.5V battery that powers the ohmmeter circuit.
 
You must log in or register to reply here.
Back
Top