Connecting a Moving Coil Meter to a 4-20mA Signal

What resistance do you measure, using the Fluke DMM to look at the moving coil meter (nothing else in circuit)?

Hi, when measuring the resistance over the mA meter`s terminals, I get on my Fluke 2Mega Ohms??? I know this sounds bizaar, since an amp meter shouldn`t have any resistance or very little, but a volt meter should have high resistance.

Sounds bizaar? Sounds more like broken. If the needle isn't bent from wrapping on the stop pin, someone may have applied ac to it and fried it.

You say that you used a Fluke meter set to measure resistance of the meter and got 2 megOhms.

If it is a Voltmeter and if the needle moves freely and is was not resting tightly on the peg the Ohm meter connected should have at least caused a small deflection.

A 50 microamp 2 megohm meter would take 100 Volts DC full scale.

I previously mentioned that the meter face usually has information about what the numbers on the scale represents with multipliers or shunts installed and/or the actual meter movement characteristic like "50uA FS" unless it has been modified since.

How about some more info to work with?

Measure the resistance of the moving coil meter out of circuit then monitor the voltage across the meter. I=V/R.

"On the Fluke dc mAmp scale it shows 12mA but nothing displays on the analogue moving coil meter."

Did you connect the Fluke meter set to measure current and the moving coil Amp Meter in series and apply a current? Current on the Fluke but nil on the analog meter?

What current from the Fluke Process Cal unit made the meter needle move?

Most analog meters show their current rating on the meter face near the movement. Sometimes people put current shunts inside them and don't record the new value.

I have received new D'Arsenval Meters that had no connection at all.

Are these two meters wired in series or in parallel?

Sounds like he put them in parallel. Current meters must be put in series.

Quite.

It also sounds like the digital meter has a lower input impedance.

Of course, but really a minor issue since hooking ammeters in parallel is not a good plan from the start. In theory you could simply add the two readings but practically speaking it's a bad idea.

try a 250 ohm resister in the loop