[Test-Equipment] Leeds and Northrup KS-10376 Null Voltage Test Set

[Steve Byan]

Does anyone have any information on a Leeds and Northrup KS-10376 Null Voltage Test Set, made for Western Electric Co.? It appears to be a 4 decade Kelvin-Varley divider plus one decade wirewound pot, plus a galvanometer for the null indication, along with some switching that enables the following measurements:

1. potentiometric voltage ratio measurement, with an external +/-250 volt reference supply
2. resistor ratio measurement, with an external 45 volt dry cell battery
3. resistance measurement, with an external 45 volt dry cell battery

The decade string is 100K ohms. 

I don't have a manual; it's got a schematic varnished onto the inside of the case, and some basic operating instructions varnished onto the inside of the lid.

I hope to use this, along with homebrew stable HV and LV power supplies and an AD597 voltage reference such as the one from Geller Labs, to calibrate the DC ranges on my VTVM collection (HP-410B, HP-412A, HP-410C, Heath IM-11, a sick HP 3456A, and more to come I'm sure). I'm wondering about:

* what's it's specified accuracy? It's got a resolution of 10 ppm; was it anywhere near that accurate? (My unit was last calibrated in 1958 at Bonica Arsenal, so I have no idea what its accuracy is now. I probably can't afford to have a calibration lab look at it. I do have a couple of inexpensive Vishay 0.1% resistors, so I can at least get some idea of whether it's completely out of whack or not.)

* what's the maximum current the divider can take? I'd like to be able to compare 1KV against a 10V reference standard; with 100K resistance, the individual decade resistors will have to take 10 ma * 100 V or 1 Watt. The instructions in the lid imply a limit of 250V, or 1/4 Watt per resistor.

* what's the sensitivity of the galvanometer? I'd like to be able to feed the divider from the 10V reference and set my low-voltage supply to 1V or less. I suspect the galvanometer isn't sensitive enough for these low voltages; I'm contemplating adding a couple of banana jacks so I can use my HP 425A DC micro volt-ammeter as a more sensitive null detector.

Eventually I hope to tinker up an AC calibrator, too.

Or should I just look for a used HP 738AR or 738BR?

Best regards,
-Steve

-- 
Steve Byan <stevebyan at me.com>
Littleton, MA 01460