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KB2VXA > TECH 28.11.16 13:26l 44 Lines 1491 Bytes #999 (0) @ WW
BID : 25888_VK6ZRT
Read: DK3UZ DF7EAV GUEST DG4IAK OE7FMI
Subj: Re: Current Voltmeter
Path: DB0FHN<DB0PM<OE2XZR<OE5XBR<OE1XAB<HG8LXL<N0KFQ<VK6ZRT
Sent: 161128/1047Z @:VK6ZRT.#BUN.#WA.AUS.OC #:25888 [Boyanup] $:25888_VK6ZRT
From: KB2VXA@VK6ZRT.#BUN.#WA.AUS.OC
To : TECH@WW
Hi fellow old buzzard techs,
"Voltmeters using current give correct values only in circumstances where the current through the
instrument is so small that it does not appreciably change the potentials to be measured."
This brings back memories of troubleshooting vacuum tube/valve receivers.
Remember hollow state? A 50,000 ohms per volt VOM couldn't be used for
measuring the AVC voltage, internal resistance was low enough to drag it
down. That's one of those situation where a VTVM with an 11M internal
resistance was used. I hope you didn't throw yours away and replace it with a
FETVOM, FETs unfortunately are sensitive to RF so most can't be used to
diagnose transmitter problems.
"Such a voltmeter cannot be used for alternating currents."
Sure it can, both my VOM and VTVM have rectifiers inserted on the AC scales.
(;->)
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"New Jersey, the most American of all states. It has everything from
wilderness to the Mafia. All the great things and all the worst,
like Route 22."
Jean Shepherd K2ORS (SK) & WOR radio personality
73 de Warren
Station powered by JCP&L atomic energy, operator powered by natural gas.
Message timed by NIST: 28-Nov-2016 at 10:47 GMT
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