The May 1969 issue of Popular Electronics has plans to make a 5 Amp. AC
Ammeter out of a BC-442 meter. It uses 300 ohm twin lead as a 0.1375 ohm
shunt. They show 31" plus 1/2" for connections at each end. I have the
proper meter but never acquired the thermocouple.

K3HVG wrote:
Well, they could be either a self-contained meter; one that one hooks up
directly, inline/series, with the RF current and the other is as you
have described. If the meters are not of the sealed type, you can
remove the movement from the shell and have a look. Try and see if
there's a thermocouple mounted somewhere as an integral part of the
unit. Meters, like on the TCS, BC-191/375, and the ART-13 for example,
are self-contained. They generally all work the same, its just where
the thermocouple is located. That's my observation on the subject.....

terryS wrote:
Came across a couple of those RF antenna current meters. Typical they
have a scale up to three of five amps. One is US and other is UK war
surplus.
AIUI the meter movement is driven by a small DC current produced from
the output of the thermocouple.
The thermocouple being heated by the RF current. Looks like the meter
itself is a one or five milliamp movement. Can anyone comment/advise?
Thanks.

Richard Hall wrote:
The May 1969 issue of Popular Electronics has plans to make a 5 Amp. AC
Ammeter out of a BC-442 meter. It uses 300 ohm twin lead as a 0.1375 ohm
shunt. They show 31" plus 1/2" for connections at each end. I have the
proper meter but never acquired the thermocouple.

What type is the thermocouple? If it's a Type J or K, I probably have
some junk box stuff.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Richard Hall writes:

The May 1969 issue of Popular Electronics has plans to make a 5 Amp. AC
Ammeter out of a BC-442 meter. It uses 300 ohm twin lead as a 0.1375 ohm
shunt. They show 31" plus 1/2" for connections at each end. I have the
proper meter but never acquired the thermocouple.

K3HVG wrote:
Well, they could be either a self-contained meter; one that one hooks up
directly, inline/series, with the RF current and the other is as you
have described. If the meters are not of the sealed type, you can
remove the movement from the shell and have a look. Try and see if
there's a thermocouple mounted somewhere as an integral part of the
unit. Meters, like on the TCS, BC-191/375, and the ART-13 for example,
are self-contained. They generally all work the same, its just where
the thermocouple is located. That's my observation on the subject.....

terryS wrote:
Came across a couple of those RF antenna current meters. Typical they
have a scale up to three of five amps. One is US and other is UK war
surplus.
AIUI the meter movement is driven by a small DC current produced from
the output of the thermocouple.
The thermocouple being heated by the RF current. Looks like the meter
itself is a one or five milliamp movement. Can anyone comment/advise?
Thanks.


It is the BC-442 antenna current meter. I built the meter from the article.
Still use it.

Fair Radio had the thermocouple units-- now out of stock, but it might
be worth an email.

Steve.
--
Steven D. Swift, , http://www.novatech-instr.com
NOVATECH INSTRUMENTS, INC. P.O. Box 55997
206.301.8986, fax 206.363.4367 Seattle, Washington 98155 USA