Forums :: NEW! Web Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Jul Sun 25, 2021 10:07 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 29 posts ]  Go to page Previous  1, 2
Author Message
 Post subject: Re: What makes a multimeter a "multi"meter and not a VTVM?
PostPosted: Jun Sat 05, 2021 7:46 am 
Member

Joined: Jun Fri 19, 2009 6:34 pm
Posts: 10709
Location: Long Island NY
The Voltohmyst was the brainchild of John F. Rider who designed it in 1939 and had his Service Instruments Company build it. Rider held the patent on the 1 megohm (or more) tip resistor. Interestingly enough, the original Voltohmyst only measured DC voltages up to 5-kV, and resistance. No AC volts and no current. A year later Rider came out with the Channaylist.

Rider apparently decided the test equipment business was not to his liking because he sold Service Instruments to RCA which then incorporated it into their dealer and special products line.

_________________
"Hell, there are no rules here--we're trying to accomplish something!"

Thomas A. Edison


Top
 Profile  
 
 Post subject: Re: What makes a multimeter a "multi"meter and not a VTVM?
PostPosted: Jun Sat 05, 2021 9:42 pm 
Member

Joined: Jan Tue 16, 2007 7:02 am
Posts: 4577
Location: Lexington, KY USA
Just for fun, looked through the test equipment pages of a 1935-1936 Radio Master.

A couple of manufacturers called some of their meters "Multimeters", so the term was common already at that time.

I actually did not see the exact term "VOM" used, but rather "Volt-Ohm-Milliammeter", used by many makers.

Ted


Top
 Profile  
 
 Post subject: Re: What makes a multimeter a "multi"meter and not a VTVM?
PostPosted: Jun Sun 06, 2021 4:13 pm 
Member
User avatar

Joined: Nov Fri 10, 2006 12:24 am
Posts: 2984
Location: Thornhill, Ontario, Canada
KX5JSC wrote:
... And a minor niggle: isn't "analog VTVM" a redundancy? John
Yes, but sometimes redundancy clarifies an issue.
Cheers,
Roger

_________________
Roger Jones,
Thornhill, Ontario
Ontario Vintage Radio Assoc. http://www.ovra.ca


Top
 Profile  
 
 Post subject: Re: What makes a multimeter a "multi"meter and not a VTVM?
PostPosted: Jun Sun 06, 2021 5:27 pm 
Member
User avatar

Joined: May Wed 18, 2011 2:40 am
Posts: 5565
Location: Littleton, MA
General Radio made a digital VTVM, the Type 1820-A with the 1820-P1 Multimeter/UHF Voltmeter plug-in.
Image

See viewtopic.php?p=2909190#p2909190

The 1820-P1 appears to be their 1806-A Electronic Voltmeter, minus the analog meter. The 1806-A is a hybrid tube and transistor analog VTVM.

_________________
Steve Byan https://www.byan-roper.org/steve/steve-at-play/


Top
 Profile  
 
 Post subject: Re: What makes a multimeter a "multi"meter and not a VTVM?
PostPosted: Jun Tue 08, 2021 5:10 pm 
Member

Joined: Dec Sat 28, 2019 4:18 pm
Posts: 977
Location: Corinth, TX
engineer wrote:
KX5JSC wrote:
... And a minor niggle: isn't "analog VTVM" a redundancy? John
Yes, but sometimes redundancy clarifies an issue.
Cheers,
Roger

And _I_ keep telling people, "Avoid redundancy." Alas, no one seems to listen. :( :(

OTOH, redundancy is the essence of successful speeches: Tell them what you are going to tell them (the intro). Tell them (the main body). Then, tell them what you told them (the summary).

John


Top
 Profile  
 
 Post subject: Re: What makes a multimeter a "multi"meter and not a VTVM?
PostPosted: Jun Tue 08, 2021 5:15 pm 
Member
User avatar

Joined: Nov Wed 30, 2016 7:35 pm
Posts: 10457
Location: Sunbury, Ohio 43074
Redundancy is the engine that drives us (crazy). For example:

This is a message from your department of redundancy department. This message will not be repeated. I repeat, this message will NOT be repeated.

_________________
Preserving the hist. of electronics, one boat anchor at a time! :)
https://www.bbtvtestequipment.com


Top
 Profile  
 
 Post subject: Re: What makes a multimeter a "multi"meter and not a VTVM?
PostPosted: Jun Tue 08, 2021 11:01 pm 
Member
User avatar

Joined: Jan Sun 15, 2012 4:20 pm
Posts: 681
Location: Lawton Oklahoma
The RCA Master Voltohmyst does measure current and has a meter the size of your head.

There is a seller on Ebay who has for years been selling a reproduction manual for the Simpson 260 Series 6 and 6M VTVM
As far as I know there has never been a Simpson 260 VTVM , only a VOM unless it refers to an adaptor you can purchase to convert it.


https://www.ebay.com/itm/303128274670?h ... Sw-jhT-jEQ


Top
 Profile  
 
 Post subject: Re: What makes a multimeter a "multi"meter and not a VTVM?
PostPosted: Jun Wed 09, 2021 1:52 am 
Member
User avatar

Joined: Oct Thu 18, 2007 11:34 am
Posts: 3934
Location: Port Orchard, Wa 98366
Couple of points.
The older pre-transistor VOMs had a 22 volt battery, so a caution was sent out not to use them on transistors because the transistors would be overvoltaged and poof! VOMs were considered as passive devices (batteries only). they are still preferred when working/troubleshooting medium and high powered transmitters.

Although I wouldn't necessarily say "UH Contraier !" but my experience when I was using a Simpson VOM, with a breaker, with Naval transmitters around 500-1,000 watts using 500 to 1,000 watt lightbulb load. Being at my workbench with less than 100 feet distance, I was working on calibration/troubleshooting of a URC-9 and the Meters circuit breaker would pop to open (it was when the transmitter was transmitting :shock: ).
--------------------
VOMs
There were only a few differences as far VOMs go. with exceptions the meters had either a
1000 ohms / volt, with sensitivity of 1mA
5,000 ohms / volt, with a voltage sensitivity of 10 uA
or 20,000 ohms / volt, with a voltage sensitivity of 100uA
and 100,000 ohms / volt, with a voltage sensitivity of 100uA
--------------------
VTVMs
The VTVM has a tube ex: 12AX7 which amplification making it more sensitive and with an attached probe of 10 Meg-ohm and the VTVM with 1 Meg-ohm and the VTVM Having a Total of 10 Meg-ohms = total of 11 Megaohms.
(Also can be used on R.F. because of the probe (EX: HP- 410-C )
Analog meters have this advantage of Measurements where the are much slower in response than a digital Meter. :wink:
Simpson had 2 VTVMs Models' 303 and 266

Steve Johnson shows a catalog on His web page.
Image

_________________
Visit our site:
http://antique-radio-lab.forumotion.com/
I was smokinradios Long time ago (2004)


Top
 Profile  
 
 Post subject: Re: What makes a multimeter a "multi"meter and not a VTVM?
PostPosted: Jun Sat 19, 2021 1:15 am 
Member

Joined: Dec Wed 27, 2017 3:05 pm
Posts: 43
Location: Little Rock, AR
re: VTVM

I still keep a well calibrated WV-98 Senior Voltohmyst on my workbench. I find it extremely useful, even though I have two 3486A HP digital bench meters and an HP971A portable and a couple of scopes handy. Sometimes the big old analog meter with a probe connected to the super high impedance grid of a 12AU7 vacuum tube will give the quickest and most useful answers, all things considered.

Other Analog meter applications of choice for me include;

I keep Weston current and voltage meters permanently configured into my bench AC power to provide a constant reference for voltage stability as well as current draw. They're both analog. I can see them out of the corner of my eye, and they are passive and very accurate.

I also use a Sencore Powerite 57, another analog meter equipped device, for my first-time power up scenarios.

In what I think is my most excessive and yet wonderful use of analog metering - I also have four analog DC milliameters. I pass plate and G2 current in push-pull two tube amplifiers directly through these meters with special remote sockets I've built. These meters DIRECTLY read tube current, no shunt resistor in the socket (of course there is in the meter). Doing this, I can simultaneously monitor grid and plate current on all working elements in the circuit. Analog meters seem ideal to me for this particular arrangement. In my opinion and experience with this setup, digital meters are just too confusing to look at if you have to monitor four displays at once. In contrast, four analog needles waving gracefully and in concert reveals a lot about what's going on in a power tube pair under load.

Just my opinion...SAVE THE WIGGLING NEEDLES! :-)


Top
 Profile  
 
Post New Topic Post Reply  [ 29 posts ]  Go to page Previous  1, 2

All times are UTC [ DST ]


Who is online

Users browsing this forum: Phil Wiesing, Pierrot du 82, stevebyan, ttx450cap and 24 guests



Search for:
Jump to:  


































Privacy Policy :: Powered by phpBB