On Thu, May 1, 2025 at 02:17 PM, Razvan Popescu wrote:
I cannot find the article about the 1830A where Tegam said they used a type IV bridge and added a 6.5 digit multimeter to build the 1830A.
I'm not sure what is inside it but I assume it will use a pair of auto balancing bridges like the 432A system. I'm also assuming they use some form of 4 wire IV method to measure their own mount resistance.
It could be that the mount resistance is stable enough to not have to measure it. I'm just guessing really :)
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I mentioned 6.5 digit DVM because Keysight describe their voltage measurement as being equivalent to a 6.5 digit DVM inside the N432A. Tegam will presumably use or claim something similar.
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With the N432A I think you still have the option of connecting an 8.5 digit DVM externally to the rear of the instrument to do DC substitution the old school way. I suspect only the strictest calibration houses bother with the external 8.5 digit DVM. This probably represents the ultimate accuracy in terms of providing a highly accurate transfer standard.
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I doubt the Tegam unit supports an external 8.5 digit DVM and this probably separates the two meters in terms of ultimate performance in terms of providing a highly accurate transfer standard. I doubt the Tegam unit can compete here even this is only relevant for critical users at calibration houses. Outside a calibration house this advanced feature of the N432A isn't really relevant.?
