Simpson 150 Amp Clamp

[OliLt]

I obtained a Simpson 150 Amp Clamp as part of an estate. The included instructions indicate that this tool was originally intended to be used with an analog AC instrument with a sensitivity of 5000 ohms per volt containing either a 2.5, 3, or 5 volt scale. There is a multiplication factor that is then used to calculate the total amps depending on the volt scale used.

Can this tool be used with a digital multimeter? The scales on my meter are much broader that 2.5, 3, 5 volts AC.
 

[Ted in NE-OH]

Yes, if you shunt the input to the DVM with a 5000 (5K) resistor.
 

[tech4]

That is 5000 ohms per volt. To use the 3 volt scale you would need 3 X 5000 or 15000 ohms (15K)
 

[Ted in NE-OH]

Tech4 you are right, I stand corrected
 

[OliLt]

I am getting lost in the discourse. Suppose I set my DVOM to the 2 volt scale. What do I need to do to?
 

[tech4]

You will have to do some interpolation. Your digital meter should have a high input impedance and be a negligible load. You could use 2.5 as full scale but you would need a 12500 ohm resistor which is not common. 15000 is very common and you would use 3 volts as full scale. The scale on your digital meter should make no difference as long as it is above 3 that is 10 or 20 vac.
For instance on the 300 amp scale the meter would read 3 volts or 200 amps will read 2 volts.

On the red 12 amp scale the multiplier is 4 and 3 volts = 12 amps of 2 volts =8 amps and so on
If I was doing it, I would use a 20K potentiometer and place across the meter leads and calibrate the reading to match the reading of a known good meter.
 

[john *.?-!.* cub owner]

The simplest thing would be to find an old Simpson 260 meter and use it. Or a better idea may be to go on Ebay and buy one of the new digital AC/DC amp clamps for around $25.
 

[OliLt]

Ok, I'm beginning to get it. Just one clarification: should the resistor, or potentiometer be in series or parallel with the meter leads. Thanks for your response.
 

[MarkB_MI]

The shunt is in parallel with the meter leads. You're lowering the input impedance of the multimeter so it looks like it's an analog voltmeter. If possible, get a precision (1%) resistor. Radio Shack resistors are typically 5%, which is enough to affect the accuracy of your readings.
 

[tech4]

Yes it should be in parallel. Or as suggested find a Simpson 260 or Triplett 630 or 310.
The Simpson has a 2.5 volt scale and Triplett has the 3 volt scale.
I still love my old Simpson 260 except when I need a precision measurement. I like to see that meter swing!