ITTSB.EU Blog Forum
Electrical Metrology | Measurement Tips & Products | Calibration standards => Electrical Standards & calibration accessories => Topic started by: Kiriakos GR on November 09, 2026, 02:19:11 PM
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Decade Resistor, Type 510-AA 0.010 ~ 0.1 Ohm, 2%, 4A.
This is the most wild designed decade resistor :)
But I did challenged my own brain cells, so to discover of why this ancient monster, this was designed for?
General Radio = a brand standing since 1915.
Oldest design of Milliohm meter this was designed for testing of wires and not of electronic components.
Telephone lines inspection, they were requiring having a Milliohm meter, and the usual test current this was at 1A.
Decade Resistor, Type 510-AA this supports 4A as Max.
And in conclusion 8)
If you were after checking linearity of your high-power Milliohm meter, the most smart choice of that era, this was using one Decade Resistor, Type 510-AA.
If this 510-AA were redesigned to to serve modern metrology, this would have 4W support instead of 2W.
Even so, for Telephone lines inspection with a Milliohm meter this using a needle, this is unable to measure strict tolerances.
Siemens (Thomson) M273-A1 Kelvin measuring wiring tester (milliohm meter) (https://www.ittsb.eu/forum/index.php?topic=1440.0)
In the positive side of things, this is an inexpensive relic at the used market place. :)