[Amps] plate voltage meter shunt

[Jim Thomson]

Date: Sat, 3 Nov 2012 14:15:44 -0700 (PDT)
From: Douglas Johnson <w9iix1 at yahoo.com>
To: AMPS <amps at contesting.com>
Subject: [Amps] plate voltage meter shunt

I am installing a meter to measure plate voltage 1-5000v@ 1a?dc, the meter has a 1ma fs rating. ?the serial resistance I have made up in the past has been 3 watt metal film resistors in series. since they can only rated for 200v per resistor it takes many to do the job. Can some other resistor type with a higher rating?be used in a safe manner for this purpose?...tnx, Doug,w9iix

##  it’s a meter multiplier string..and not a shunt !    You can buy  1% tol 3 kv rated resistors  and also 1% tol  10 and 15 kv rated  resistor’s... from mouser.   5000/.001 = 5 megohms.     Use  10 x 500K ohm resistors in series. 
I mount em on either perf board or drill out some micarta,  plexiglass, or  UHMW.  Just mount em so they go down one side,across, and back up the other side.   I mount the entire assy  directly to the meter studs !  
To pull that off, you need to make the board big enough. The  usual deal is to make it rectangular shaped, taller than wider, then whack two holes for the meter studs towards the  top of the board..with the rest of the board hanging down. 

## you can mount the board in a few diff configs.   The idea is to keep the 5 kv end well  away from the meter itself.    5 kv enters resistor #1...... and exits  #10..then onto the positive of the meter.   NEG of meter goes DIRECTLY to the
B-  end of the HV supply.   Take is directly to the B- end of the HV caps if you can at all possible.   Don’t do some arrl fubar and  run it to the chassis.  

##  On my hb amps, I use a HV fuse in series with the 50 ohm glitch resistor... in series with the B+.    In those cases,  I use one HV meter in the HV supply, and a 2nd HV meter in the RF deck itself.  If the HV fuse blows open,
the HV meter in the HV supply will still read 5kv.     The HV meter in the RF deck will  read ZERO.  This is done for safety purposes.  In some cases,  I will use a 3rd box, full of HC caps.... and that box also gets it’s  own HV neter. 

later....... Jim   VE7RF