Products > Test Equipment
Keysight's new 34465A (6.5 digit) and 34470A (7.5 digit) bench multimeters
6thimage:
--- Quote from: economist on March 23, 2015, 08:17:33 pm ---
--- Quote from: dadler on March 23, 2015, 08:01:57 pm ---Hmm. Darn? I was hoping it was a bug. My Brymen BM869 and Fluke 287 seem to handle DC+AC just fine. Granted, at no where near the same accuracy/resolution. But still. Thanks for the data-point.
--- End quote ---
I was thinking the same thing (that hand held meters with secondary display seem not to have this issue) and thought perhaps the cause was the resolution. But, turning down the resolution on the DMM7510 does not change things -- I still get that clicking relay.
--- End quote ---
Why would changing the resolution make any difference? The AC and DC take difference paths in the meter, those that click use a relay to change between the paths, those that don't are either using a multiplexer (to silently switch between the paths) or have two measurement circuits - I'm guessing not many, if any at all, have two measurement circuits.
So the question is why did they choose to use a relay rather than a multiplexer? Perhaps, they can achieve a better signal integrity with a relay?
With the 61A, it is an added feature, so you can't expect it not to click, considering changing from DCV to ACV on the front panel causes a relay to click. Whilst the 65A and 70A are designed so the board is common between all of the models (including the 60/61A), they could have potentially used a multiplexer instead of the relay (unless it compromises the measurements). But my guess is that they were never electronically designed for dual measurements (AC/DC wise), but they wanted to add it into the firmware as an extra feature, with the hope that it might be useful.
I think, in their minds at least, if you need to measure both AC and DC constantly, you will have two multimeters set up.
economist:
Here is a quick video of the switching on the Keithley DMM7510. The source is 1V output from a Rigol DP832.
https://vimeo.com/user20472841/review/123033131/1f78e82b29
dadler:
--- Quote from: 6thimage on March 23, 2015, 09:38:28 pm ---
--- Quote from: economist on March 23, 2015, 08:17:33 pm ---
--- Quote from: dadler on March 23, 2015, 08:01:57 pm ---Hmm. Darn? I was hoping it was a bug. My Brymen BM869 and Fluke 287 seem to handle DC+AC just fine. Granted, at no where near the same accuracy/resolution. But still. Thanks for the data-point.
--- End quote ---
I was thinking the same thing (that hand held meters with secondary display seem not to have this issue) and thought perhaps the cause was the resolution. But, turning down the resolution on the DMM7510 does not change things -- I still get that clicking relay.
--- End quote ---
Why would changing the resolution make any difference? The AC and DC take difference paths in the meter, those that click use a relay to change between the paths, those that don't are either using a multiplexer (to silently switch between the paths) or have two measurement circuits - I'm guessing not many, if any at all, have two measurement circuits.
So the question is why did they choose to use a relay rather than a multiplexer? Perhaps, they can achieve a better signal integrity with a relay?
With the 61A, it is an added feature, so you can't expect it not to click, considering changing from DCV to ACV on the front panel causes a relay to click. Whilst the 65A and 70A are designed so the board is common between all of the models (including the 60/61A), they could have potentially used a multiplexer instead of the relay (unless it compromises the measurements). But my guess is that they were never electronically designed for dual measurements (AC/DC wise), but they wanted to add it into the firmware as an extra feature, with the hope that it might be useful.
I think, in their minds at least, if you need to measure both AC and DC constantly, you will have two multimeters set up.
--- End quote ---
But changing from DC to AC, at least on the 34465a, does not cause any relay click.
HighVoltage:
--- Quote from: dadler on March 23, 2015, 10:55:16 pm ---
But changing from DC to AC, at least on the 34465a, does not cause any relay click.
--- End quote ---
On the 34470A and the 34401A a relay clicks, when switching between AC and DC measurements.
6thimage:
--- Quote from: dadler on March 23, 2015, 10:55:16 pm ---But changing from DC to AC, at least on the 34465a, does not cause any relay click.
--- End quote ---
I have been told (in the last hour or so) otherwise - I'm not sure if the relay will click when the meter is in its stopped mode (i.e. not taking measurements), I think it probably would, but it might be a reason why you are not hearing it.
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