General > General Technical Chat
AC Voltage Calibration Source - Not Super Accurate/Expensive
EPAIII:
What would you use as a sine wave, AC Voltage source for a rough check of meters? I am sure there are expensive sources that probably have an accuracy of a very small fraction of a percent, but they probably cost a large fortune. I am asking about something perhaps between 1% and 0.1% and with an affordable price (well under $1,000 USD).
It should at least cover AC power frequencies and Voltage levels. I would assume that precision resistors could be used to divide it's output down to lower Voltages.
BrianHG:
Have you looked into precision function generators. Though, this will not be a proper high voltage reference, but with the ~15v ac range, you may end up with a multipurpose device. You should be able to achieve better than 1% precision with a DAC synthesized output unit.
Asking users in the TEA or Test Equipment, or Metrology threads would probably give you more authentic hardware choices to choose from.
AVGresponding:
If you're patient and have a good spread of search strings on the likes of eBay, and check regularly, you can find something nice and/or useful eventually.
I scored a fully working (with only minor cosmetic issues) Boonton RFL (may also be branded Clarke Hess) 828 AC/DC V/I source for (icr exactly) somewhere around $100. It has 1-1kV, 1mA-10A (5A max) ranges with 4-decade adjustment, and does 50, 60, and 400Hz in AC.
The claimed accuracy is +/-0.05% of setting for voltage plus 0.05% of range for DC and 0.1% of range for AC. For current it claims +/-0.1% of setting plus 0.1% of range for DC and AC.
Since it's a US manufacturer, I would expect it to be easier and cheaper to find on your side of the pond.
David Hess:
For low voltage calibration, I chop a precision DC source into a square wave with exactly 50% duty cycle which can be used for AC calibration with RMS and average responding values which can be calculated.
However a sine wave source is required for calibrating the AC frequency response, but it only needs to be leveled because once the frequency response calibration is done, the precision square wave can be used to calibrate level.
mawyatt:
Awhile back we developed a DMM & Scope Device just to "check" our various instruments.
https://www.eevblog.com/forum/testgear/ac-rms-dmm-tests/
Note the last couple posts where we had to replace the Voltage Reference which died for some unknown reason. Likely we shorted one of the exposed banana plugs to something, as we are not exactly "gentle" and it gets tossed around the lab, but do try and keep it powered 24/7.
This device has been used to "verify" handhelds Fluke 77 and 87, U1233A & UT210E. Also used for lab bench 6 1/2 digit DMMs HP34401A, AG34401A, SDM3065X, three KS34465A (light and 2 dark) and a Keithley DMM6500 as well as our DSOs.
We were curious as to how the old analog IC RMS converters behaved verses the Digital RMS Computational Methods in the KS34465A and DMM6500. So comparing the 34401A vs. the 34465A and DMM6500 reveled the analog IC RMS techniques held up very well indeed :-+
Of course YMMV.
Edit: Just did quick "Turn on and Read" each instrument, no proper warm up and the lab temp is ~24C and humidity ~58% (normally ~26C & 45%). OK need to warm up the lab it's cold here (~15C), so justifies turning on all these instruments :-+
Handhelds:
35 year old Fluke 87 2.502VAC (never calibrated)
KS U1233A 2.507VAC
UT210E 2.45VAC
Bench: Analog RMS Converters
HP34401A 2.50005VAC
AG34401A 2.49978VAC
SDM6500 2.49723VAC
Bench: Computational RMS
DMM6500 2.499945VAC
KS34465A-1 2.5000405VAC
KS34465A-2 2.4998607VAC
KS34465A-3 2.4999653VAC
So think one can surmise that this square-wave technique described in the link above is acceptable to quickly verify typical DMMs used in repair and around the lab with AC RMS, and are working properly, or not!!
Read is NOT a claim to ultimate precision, altho one would have difficulty arguing against this technique and results, but simply an easy, low cost, simple, means to VERIFY a DMMs proper AC operation within the constraints of the squarewave stimulus.
Best & Happy Holidays,
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