LF: Re: Vintage RF current meter

["Alan Melia" <alan.melia@btinternet.com>]

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 -----

From: VIGILANT Luis Fernández

To: rsgb_lf_group@blacksheep.org

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 :-)

 

https://dl.dropboxusercontent.com/u/7162072/Fotos%20varias/MF/IMG_20160504_091006.jpg

 

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