Electronics > Metrology

ADCMT 7480 or Advantest 6581T

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bastl_r:
I know it's a crazy thought.
But if I really wanted to immerse myself in the world of 8.5-digit measurement technology and was faced with the choice of buying an ADCMT 7480 or an Advantest 6581T, which one should I choose? The technology in both is roughly the same i think.
Which reasons would speak in favour of the ADCMT and which in favour of the Advantest?
Are there any reasons that speak completely against one or the other device?
What should I look out for in any case?
I don't really need an AC measurement.

Regards bastl_r

Kleinstein:
The advantage of the old 6581 is that there is a reverse enginered schematics available, if needed for a repair. As a downside the displays are often dim and a replacement is a bit tricky.
A know weak point for the 6581 is the rather large current spike from AZ switching - this can be an issue with some signal sources. Another point is that ACAL may not be fully accurate for the highest resistor ranges. So the specs there may be a bit overly optimistic. Quite a few of the old meters also have a relay power saving mode not working right that can cause some thermal EMF error that can effect the lower voltage ranges - this is fixable at least.
The 6581T tends to have a rather poor factory calibration that causes quite some INL error - so while the ADC is essentially the same as with the full version, the linearity is not that great for the T version. There may be ways to correct this, but it is extra effort and may need extra instruments (e.g. cal source).

branadic:

--- Quote ---The 6581T tends to have a rather poor factory calibration that causes quite some INL error - so while the ADC is essentially the same as with the full version, the linearity is not that great for the T version. There may be ways to correct this, but it is extra effort and may need extra instruments (e.g. cal source).
--- End quote ---

I'm not sure this applies to the T models only, as I had the same issue on my D model. I would rather guess it's a general issue for all three models. The only thing known is that some nice INL figure was shown in some paper, where they probably applied individual INL constants to that specific meter, while all meters available on the secondary market seem to contain general and always the same coefficients.

-branadic-

Mickle T.:
As I have already written several times, both of these multimeters are not of the metrological type, but are technological and are used in equipment for functional testing of microcircuits and semiconductors.
ADCMT 7480T (there is an error in the topic title - ADCMT 7480 does not exist) is designed as a cheaper replacement for the Advantest 6581T model. ADCMT 7480T:
- lacks current measurement,
- does not have higher resistor measurement ranges,
- does not support high-speed measurements,
- there is no documentation at all,
- circuit diagrams are still available only in the form of fragments,
- firmwares are not available,
- it is unknown whether there is a problem with INL and whether it is possible to solve it using software, as was the case with the R6581x.

aronake:
Maybe you should not get too blinded by the 8.5 digits.

A Keithley DMM7510 may serve your needs very well. They start to come up used at not insanely crazy prices. Still a bit more expensive than an Advantest or ADCMT. But more linear, less noise, a modern user interface, documentation, spare parts avilable (as compared to the Advantest screen).

The DMM7510 also not a metrology multimeter. I think only 3458a, Transmille and the fluke 8.5 digits would classify as that. But it is not that far after 3458a in most measurement areas. Almost as low noise, better temperature stability, quicker warmup, a modern gui, smaller, lots of other features etc. It lack artefact calibration, but you likely will not adjust it yourself anyway.

Or just realize that you are falling into the voltnut abyss and save your self some future problem and buy a 3458a directly. ;) If you find a good used one, you could see it as an inflation protected asset.

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