[Amps] caps SB200

[Will Matney]

Bob,

That resistor is really high resistance. Did you check it with an ohmmeter on the correct resistance? You may need to use a VTVM to read this high of a resistance. On a Simpson 260, the meter is ran at 20,000 ohms per volt if I recall correctly. Other meters can be different. To determine the value of the resistor needed, you need to use this number. For instance, if using the 1000 Vdc full scale, you would need a 20 megohm resistor (1000 x 20,000). Then for a 5000 Vdc range you would need a 100 megohm resistance total. The resistor for the probe then would be 100 Megohms minus 20 Megohms equaling 80 megohms for a 5 kV full scale reading. So if yours is similar, you'd be looking at an 80 Megohm resistor! I have seen some meters use 40,000 ohms per volt so this could be double. You would need to know what the probes voltage rating is, or figure it by the resistance. Some were made for TV service for pic tube anode voltages at about 40 kV. My Simpson probes are 10 kV and 5 kV. However they did make one for 40 kV I think.

To buy a replacement resistor, you'd probably have to contact a resistor company that makes HV resistors like these or maybe Simpson. If the probe was to be bad, it could be fixed or converted to any voltage you want.

Best,

Will

*********** REPLY SEPARATOR  ***********

On 8/20/05 at 2:44 PM Bob wrote:

>Good afternoon, Will.... First, thanks for all of your posts to the 
>various forums, they have been very informative, and helpful. A real 
>learning experience.    The current exchanges about the HV on a '220 had 
>me looking at a HV probe that followed me home from a hamfest. 
> The probe is not marked with a mfg, or any numbers.  On checking the 
>resistor inside, it does not 
>conduct.                                     The resistor is marked 
>"1090  2%      HV 22     221"   6" long, threaded on both ends.
>
>Question:  Are  these type of resistors available?  Or should I look for 
>a new probe?    The piece is older, the lead has a 1/4" phone plug on it. 
>
>Thanks for your advice.   Bob McLeod  WA1RM