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Simpson 150 Amp Clamp


 
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OliLt
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PostPosted: Thu Feb 07, 2013 1:14 pm    Post subject: Simpson 150 Amp Clamp Reply to specific post Reply with quote

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.
 
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Ted in NE-OH
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PostPosted: Thu Feb 07, 2013 1:59 pm    Post subject: Re: Simpson 150 Amp Clamp Reply to specific post Reply with quote

Yes, if you shunt the input to the DVM with a 5000 (5K) resistor.
 
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tech4
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PostPosted: Thu Feb 07, 2013 2:23 pm    Post subject: Re: Simpson 150 Amp Clamp Reply to specific post Reply with quote

That is 5000 ohms per volt. To use the 3 volt scale you would need 3 X 5000 or 15000 ohms (15K)
 
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Ted in NE-OH
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PostPosted: Thu Feb 07, 2013 2:54 pm    Post subject: Re: Simpson 150 Amp Clamp Reply to specific post Reply with quote

Tech4 you are right, I stand corrected
 
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OliLt
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PostPosted: Thu Feb 07, 2013 6:10 pm    Post subject: Re: Simpson 150 Amp Clamp Reply to specific post Reply with quote

I am getting lost in the discourse. Suppose I set my DVOM to the 2 volt scale. What do I need to do to?
 
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tech4
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PostPosted: Thu Feb 07, 2013 6:54 pm    Post subject: Re: Simpson 150 Amp Clamp Reply to specific post Reply with quote

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.
 
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john *.?-!.* cub owner
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PostPosted: Thu Feb 07, 2013 7:23 pm    Post subject: Re: Simpson 150 Amp Clamp Reply to specific post Reply with quote

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.
 
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OliLt
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PostPosted: Thu Feb 07, 2013 7:31 pm    Post subject: Re: Simpson 150 Amp Clamp Reply to specific post Reply with quote

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.
 
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MarkB_MI
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PostPosted: Fri Feb 08, 2013 2:52 am    Post subject: Re: Simpson 150 Amp Clamp Reply to specific post Reply with quote

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.
 
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tech4
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PostPosted: Fri Feb 08, 2013 7:26 am    Post subject: Re: Simpson 150 Amp Clamp Reply to specific post Reply with quote

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!
 
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