Products > Test Equipment
Bench multimeter
mawyatt:
--- Quote from: KungFuJosh on June 26, 2023, 02:35:25 am ---I've been running the SDM3055X-E firmware on my SDM3045X for over a month with no issues. 5.5 digits, and no issues with the calibration or accuracy.
Thanks,
Josh
--- End quote ---
How do you know about the relative accuracy? Do you have a verifiable reference to compare against, or a known good higher resolution/accuraracy DMM to compare?
Extra digits are fine, but they need to "mean" something, rather than justing "being there"!! As we've said, "Real Precision, gets Real Expensive, Real Quick"!! If you wander over to the Metrology section you'll find a number of folks have investing significant time and $ in such.
Ultimately the "Goodness" of a DMM can be traced to the voltage reference and divider resistors, why some of the better ones employ LM399 or LTZ1000 references, some even aged and selected for low noise. The reference utilized in a given bench DMM is a good indicator of what to expect regarding performance in measurements (of course this can be hosed up with an overall poor or sloppy design).
The historic HP34401A actually has more digits available than shown on the display, some folks have addressed these "extra" digits and utilized such to extend the 34401A resolution beyond 6 1/2 digits, and from the results they've posted these aren't just "random digits" :-+
Best,
KungFuJosh:
It feels accurate. 🤣
I'm sure somebody with the resources and desire could test and/or calibrate this better than I could. I don't see any odd behavior or inconsistency from it, and it's not less accurate than my other meters. I could throw some kelvin probes on it and compare the 4W Ω test mode with my TH2830, but who knows if either of them are properly calibrated.
mawyatt:
There are some reasonably priced voltage references like the one's from voltagestandard.com (VREF10-001 R9) that are characterized with a certified Keysight 3458A. They even offer a recalibration at a charge of $15 + shipping.
Best,
KungFuJosh:
--- Quote from: mawyatt on June 26, 2023, 03:58:15 pm ---There are some reasonably priced voltage references like the one's from voltagestandard.com (VREF10-001 R9) that are characterized with a certified Keysight 3458A. They even offer a recalibration at a charge of $15 + shipping.
Best,
--- End quote ---
I want one of those, but they've been out of stock for a while.
I tried getting a couple reference devices from other sources, and they were crap. Either not marked with target numbers, or inconsistency across the board.
Kleinstein:
The 3045 / 3055E use cheaper parts for the reference (Ref5025 vs max6225) and also cheaper single resistors for the divider and Ohm part. So one can can expect more TC and more aging from those parts. However the noise from the amplifier and ADC, e.g. for measuring small voltages should be close. If one is after accuracy the relatively small price difference to the real 3055 can be worth it.
Checking the dift for the 3055E voltage and resistance can make sense, as the reference parts are relatively poor compared to the ADC. The ADC itself can give 6.5 digits and possibly even more. AFAIK this is available via RS232.
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