Author Topic: DMM does not stabilize when measuring resistance  (Read 4580 times)

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Offline pwnell

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Re: DMM does not stabilize when measuring resistance
« Reply #25 on: December 05, 2021, 01:53:00 am »
Also Z202 max TCR spec is 2.8ppm\K, not 0.2 ppm\K. Don't fall for "typical" specmanship from VPG on these. You cannot expect to have every random resistor meet typical spec. Short term rift of your DMM is also expected to be much bigger than one from resistor itself.

Where do you see that in the data sheet?
 

Offline TiN

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Re: DMM does not stabilize when measuring resistance
« Reply #26 on: December 05, 2021, 02:12:08 am »
Page 1, Table 1. Also my statement above comes from experience with testing hundreds of resistors (both VPG metal foil type, wirewounds and metal films).
I did explain this a bit here.
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Offline joeqsmith

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Re: DMM does not stabilize when measuring resistance
« Reply #27 on: December 05, 2021, 02:30:28 am »
Last one is 4 wire

Without anything to show how it was setup, I assume based on:
Quote
So here are some graphs - all same test setup:

that you are still mounting the part with the BNC inside the copper and using a 4-wire to the BNC.  All a pure guess as I can't see what you are doing.
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Offline pwnell

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Re: DMM does not stabilize when measuring resistance
« Reply #28 on: December 05, 2021, 04:23:25 am »
Very informative article, thanks.
 

Offline pwnell

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Re: DMM does not stabilize when measuring resistance
« Reply #29 on: December 05, 2021, 04:26:14 am »
Without anything to show how it was setup, I assume based on:

that you are still mounting the part with the BNC inside the copper and using a 4-wire to the BNC.  All a pure guess as I can't see what you are doing.

Sorry, it was a separate post and I used the bnc for the current wires and separate wires to the resistor from the sense terminals for that last graph only. So 4 wire, no copper tube.
 

Offline HighVoltage

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Re: DMM does not stabilize when measuring resistance
« Reply #30 on: December 05, 2021, 12:02:46 pm »

 So 4 wire, no copper tube.

Picture please .
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Offline pwnell

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Re: DMM does not stabilize when measuring resistance
« Reply #31 on: December 05, 2021, 05:57:21 pm »
Picture please .

Sure - BNC is only used because it is convenient.  BNC carries current, the other two cables are the sense leads connected close to the resistor's body.  Meter is in 4 Wire mode.



 

Offline mendip_discovery

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Re: DMM does not stabilize when measuring resistance
« Reply #32 on: December 07, 2021, 05:41:14 pm »
I see people have taken into account the errors of the resistors but you also need to be wary of the effects that your meter has.

For example, the specs talks about its accuracy specifications over 24hrs with a room temp kept within ±1°C. So a few of the ppm drift may well be because of the meter settling.

Even the test leads might have a bit of time to adjust.

Be very cautious of thermals.

But experiment, the more you look the deeper you go. Just don't end up like n00py ;-)

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