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LF: Re: Vintage RF current meter

from [Alan Melia] [Permanent Link][Original]
To: <[email protected]>
Subject: LF: Re: Vintage RF current meter
From: "Alan Melia" <[email protected]>
Date: Wed, 4 May 2016 12:14:26 +0100
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Hi Luis, the range is determined by athe thickness of the heater wire betweemn the terminals. there is a thermocouple welded to the centre of this wire and there may be a coil of wire between the t/c and the movement to set the calibration. You will find the DC resistance quoted is a function of the range. These style of meters could be found with a ramge down to 300mA though these are easily damaged. You can make the range larger as with DC meters by  using a shunt, though the calibration differs from DC levels.
 
I have not tried replacing the heater wire with a finer gauge and re welding the t/c, but it is possible.  A ferrite is easier ....see http://huprf.com/huprf/rf-current-meter/
 
Alan
G3NYK
----- Original Message -----
Sent: Wednesday, May 04, 2016 9:46 AM
Subject: LF: Vintage RF current meter

Hi xyF
 
Yesterday I got a nice gift from a local friend, Pascual EA5JF :-)
 
 
Unfortunately the current range under 1A looks unusable 
Still not opened to have a look. Seems to use a thermocouple. Is there any chance to make it
more sensible and usable for <1A currents ?
 
73 de Luis
EA5DOM
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