There weren’t a whole lot of participants in Meter Calibration night, but a couple were interesting. Joel KEOQGD from W. Omaha brought his genuine SIMPSON 260 VOM, and measured all the exhibits starting with 120 VAC (digitally determined to be 124 and a few tenths). Joel’s Simpson meter (after determining you had to look at the RED scale) suggested around 121 VAC, close enough.
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The TWELVE VOLT display (a regulated switching supply) was a little over 12.1 volts. Joel’s Simpson said right on 12 V, really close. (The other meters were from Rich ZQG, a Harbor Freight four dollar model, Rich RWJ with a multi dollar FLUKE 8020A, and Kevin NOMHK with an H/P 3478A that showed 12.1314 Volts (note the extent of decimals).
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Everybody’s meters showed the 39 Ohm resistor to be right on, 39 or 40 Ohms, and the 1k showed universally high, 1046 to 1062 range.
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TRICK QUESTION
The fun part was measuring 1 and 1/2 mA out of an analog meter set to the resistance scale. It’s a high impedance source, that is, if YOUR meter has any resistance measuring the current, it’ll reduce the perceived milliamps. Digital meters set to a higher scale like 20mA showed nearly 2mA (1.96 to 1.98 range). Setting your digital meter to the 2mA scale introduced enough resistance to limit the current a bit and give a LOW READING – 1.86 or so. Joel QGD’s analog Simpson showed 1.7 and then 1.5 on the two different ranges.
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Joel QGD won a HARBOR FREIGHT seven dollar mini digital meter for the oldest and prettiest meter while Kevin NOMHK won the other H/Freight meter for bringing in his 6 digit accuracy H/P meter and two standards, a 1.01892 Volt standard that now measures a little less, 1.018030, and a 100 Ohm reference that all the digital meters measured at 99.5 to a hundred.
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The various digital meters measured the One Volt Standard at, like, 1.018 to 1.021 (except for Kevin MHK’s 6 figure H/P at 1.018030).
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FREQ COUNTER
The 20 yr old OPTOELECTRONICS freq counter (up to 2.8 Gc) had been ‘calibrated’ by driving past commercial transmitters and adjusting the trim cap until it showed the freq. It had also been tested against a warmed up transmitter for drift, 50 cycles back and forth as it warmed up over half an hour.
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Asked to transmit low power on 146.52 because the OPTO counter is really sensitive and subject to disastrous overload if you transmit within a foot or two, 2 guys with nice new H/Ts were unable to reply within a minute or two because they didn’t have it in memory or couldn’t remember how to access it. Ultimately, all transmitters tested were within 300 cycles of .52, and in fact, may have been more accurate than the counter because the counter had been set to show a little high, 146.52016 rather than 146.51994 because it looks prettier.
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ZQG’s 20 year old Yaesu VX-5 showed ‘52032’ three hundred cycles high, while the newer H/Ts tested showed ‘52008’ and ‘52004’ (best guess probably within a hundred cycles of right on). NOTE: A few hundred cycles off on FM is fine. One kc off can be noticed as slightly distorted audio.
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