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Should I trust the Hartmann & Braun or the Fluke 🙂

Started by dsk, November 16, 2022, 04:22:47 PM

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I have this old Hartmann & Braun meter, but I do not know much about it. Its probably made around WWi
The logo was usesd between 1901 and 1933.

Are you able to tell me about my old Voltmeter 0-6V & 0-150V DC.


The voltage ranges shown look appropriate for tube radio work. 6 volt range for the filament A battery, 150 volt range for the plate B battery. Also for the bias C battery.


I got slightly confused as the article you've put next to your picture says it's for testing torch (flashlight) batteries, but then I saw that is a different version with a 0-2V and 0-6V range.
I agree with @HowardPugh that the version you have would be suitable for valve (tube) radio work. This is assuming it has a reasonable ohms/volt specification of course.

In answer to your post title "Should I trust the Hartmann & Braun or the Fluke", and given that your Hartmann & Braun meter appears to have been dropped at some time, I think I'd trust the Fluke.  ;D


By some reason I did not get this picture enclosed (Now I have resized it to smaller photo)

It is a readable difference, and that may be because the instrument was laying and not "standing" :-\

When I am holding it up right, the needel is as clos as I may see to the mddle beteen 3.9 and 4 volts. :-)


IIRC an instrument like this uses a permanent magnet, much like a telephone receiver. If the magnet should have lost strength over the decades it might also cause a deviation. Even better if it still is precise in the supposed reading position!
I wonder what the digital meter is reading in the year 2122  8)


The difference in the readings is because of the load put on the voltage source by the watchcase meter versus the load put on by the Fluke. Watchcase meter is a battery tester only, so it puts some load on the battery to get a true reading of the battery output. The Fluke is for testing voltages and current in circuit so it should theoretically put no load on the voltage source for a true reading. Usually a multimeter is 20,000 ohms/volt, where as the watchcase meter maybe 200 ohms/volt or less.  Older and cheaper multimeters were usually 1000 ohms/volt. A VTVM could be rated in the millions of ohms/volt. VTVM= Vacuum tube voltmeter. The higher ohms/volt the less load the meter puts on the circuit.


All correct, but with both meters hooked in parallel they should in fact read the same voltage.