The local surplus guy has at least three different differential meters that
have been collecting dust for decades. I have borrowed two of them (so far).

The first one is a Fluke 893A and is solid state. Although it appears to
work, it fails the very first of the performance tests. Now that I have a
full manual, I'm going to look at this a bit closer.

The second one is a Fluke 803B (I think. There is no label on it). It has
tubes. I am slowly bringing it up on a variac before messing with it. I
plan to open it up later and take a good look.

I'm not sure what the third model is, but it looks like it may be an even
older Fluke. It is on a high shelf and I haven't gone over there to lift it
down yet. I'll probably do that later this week.

At the moment, I'm just playing around with this gear and learning a few
things. In the long run, are these things worth having?

Joe Gray
W5JG

Hi Joe,
The 893 is worth having as a working instrument. The older ones are collectibles (possibly) or a source of parts. The Voltage reference is a Weston cell which will be well past it's expected life. In particular these meters have a Kelvin Varley voltage divider. This can be used without the meter section working, possibly recased. The plastic switch dials/drums do tend to crack or warp due to srinkage of the plastic though. If theK-V dividers switches are worn out, they are still a good source for precision matched resistors. Perhaps not spot on value but all the resistors in a decade will be very close in value. These can be used for voltage dividers and Hamon resistor units (google Hamon resistor and see http://conradhoffman.com/HamonResistor.html  ). They may not look much but are high performance. There are other precision resitors in these units Take care when removing them, don't apply any force or stress to the resistor body as this can affect
their performance.
 
Robert G8RPI.

From: Joseph Gray jgray@zianet.com
To: Discussion of precise voltage measurement volt-nuts@febo.com
Sent: Wednesday, 7 August 2013, 6:00
Subject: [volt-nuts] Fluke differential meters

The local surplus guy has at least three different differential meters that
have been collecting dust for decades. I have borrowed two of them (so far).

The first one is a Fluke 893A and is solid state. Although it appears to
work, it fails the very first of the performance tests. Now that I have a
full manual, I'm going to look at this a bit closer.

The second one is a Fluke 803B (I think. There is no label on it). It has
tubes. I am slowly bringing it up on a variac before messing with it. I
plan to open it up later and take a good look.

I'm not sure what the third model is, but it looks like it may be an even
older Fluke. It is on a high shelf and I haven't gone over there to lift it
down yet. I'll probably do that later this week.

At the moment, I'm just playing around with this gear and learning a few
things. In the long run, are these things worth having?

Joe Gray
W5JG

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