Electronics > Metrology

Advantest R6581 8.5 digit DMM mini teardown/repair

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>  1 mm of dry is air is good for about 10 KV
I remembered 2kV, but [1] says 3kV.  I wouldn't cut it that close though and rather err on the safe side.


Yes, about 3 KV/mm is a better number. Anyway, depending on how clean the air gap remains, electrical safety rules say 1 mm is good for 250 V (some dirt) to 400 V (clean). For 230 VAC 3 to 5 mm are recommended. These numbers no longer require rounded corners and are independent of air pressure (height).
Anyway binding posts are not completely safe, especially when used with copper lugs.
By the way the original sockets of the R6581A have a copper tube inside with a plug around it made from white metal and with the copper wiring crimped to the plugs. There is a large contact area between plug and tube, in order to reduce temperature difference and thus thermal EMF.

Regards, Dieter

A calibration service provider has explained to me that the DMM ohmmeter range of 10M, 100M, and 1000M is not functioning properly (out of tolerance).

I find it strange that the instrument is completely calibrated with exception of those ohm ranges mentioned.

Can anyone please explain the OCOMP ON/OFF feature of the R6581T (bottom left corner of attached image from Mickle T)? I suspect that they may have not selected the proper settings before performing an external calibration or during the verification process. Can anyone speak to this? The manual does not describe it. If this is the problem, where can I find instructions on how to configure this setting from the front panel?


Thank you! I am a bit under the gun because the company wants to send the instrument back soon without a complete calibration.


--- Quote from: leighcorrigall on August 23, 2021, 03:45:34 pm ---Can anyone speak to this? The manual does not describe it.

--- End quote ---

This description appears to be on section 3, page 18, number 3. I will have to translate it.  :scared:


--- Quote from: leighcorrigall on August 23, 2021, 04:00:58 pm ---
--- Quote from: leighcorrigall on August 23, 2021, 03:45:34 pm ---Can anyone speak to this? The manual does not describe it.

--- End quote ---
I will have to translate it.  :scared:

--- End quote ---

Original text:
(3) 修オフセット電圧補正機能の設定


Google Translation:
(3) Offset voltage correction function setting

For resistance measurements, a voltage is generated by passing an internal current reference through the ratio resistor. For example, if there is an offset voltage such as the thermoelectromotive force of the lead, it will be an error. The OHM-COMP function can cancel such offset voltage. When the OHM-COMP function is turned on, the measured current is applied as usual to measure the voltage, and then the voltage is measured without the measured current. The offset voltage can be cancelled by taking the difference between the two, and resistance measurement without error can be performed. The offset voltage correction function is effective in the 10 Ω range to 1000 kΩ range. In the 10MΩ, 100MΩ, and 1000MΩ ranges, offset voltage correction is not performed even if the OHM-COMP function is on.

Question: How is this feature being listed in Mickel T's ACAL steps 13 and 14 if it doesn't correct for voltage?

Should I ask the laboratory to turn this feature on before running the calibration?


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