Adding input protection to a DVM. (UNI-T UT61E)

[flat5]

I am expecting a UNI-T UT61E digital test meter to arrive at my humble dwelling 'soon'.
This video implies that a small component or two should be added to the meter to protect it to 5000 volts from arcing and perhaps save the micro processor.
Is it that simple?

Can someone tell me exactly what parts to install and where?
I'm thinking MOVs across the + and - voltage sockets. Perhaps 600v or 1000v devices.

 

[KeepItSimpleStupid]

Unfortunately, you probably won't have the room. For fun I did a search and got this: http://www.newark.com/fluke/943121/...6226261|plid|&CMP=KNC-GUSA-GEN-SHOPPING-FLUKE which is basically a 440 mA 1000 V rated fuse. If you combine it with a spark gap http://www.alltronics.com/cgi-bin/item/28P040/39/1000V-Spark-Gap, you pretty much have it EXCEPT the design has to take into account trace distances etc.

i.e. Fuse in series with the input and the spark gap after it. It would work fine in voltage mode. Current should get it's own sort of protection. My Fluke 77 has two fuses, and the 10 A range is not fused at all.

You don't know what the input circuit looks like. If there happens to be resistors at the input, it's possible to clamp later, but you do run the risk of burning things out, unless the rating of those input series resistors are increased if they exist.

A spark gap will not influence the measurement being in parallel, but you generally need a way to current limit or break a large voltage. Fuses have both a voltage and a current rating. If you apply 1000 v to a 32 V rated fuse, it's like the fuse isn't there.

 

[flat5]

Thank you, Mr. Stupid
Good ideas.
I don't expect to work with more than typical solid state device voltages but might on occasion deal with vacuum tube circuits. So the meter is ok as is I hope.
Hoping for more thoughts. I'm interested in the problem and might do something.