[Test-Equipment] Fluke current clamp probes & scopes

[Heinz Breuer DH2FA]

Fact is for all voltage measurements that the load impedance of your 
meter should be much higher than the source impedance to reduce 
measurement error. That requirement created the demand for the 
development of the VTVM.

vy 73 Heinz DH2FA, KM5VT


J. Forster schrieb:
> There is NO requirement that the source impedance (20 Ohms) match the load
> impedance (1 MOhm) UNLESS you are dealing with RF where there is a need to
> "match" the impedances to reduce reflections.
> 
> The Load Impedance spec of 1 MOhm is to maintain the calibration of the
> probe (V/mA).
> 
> The probe, most likely, has a current transformer and a resistor across
> its secondary inside.
> 
> The Fluke info is entirely reasonable.
> 
> Best,
> -John
> 
> ===================
> 
> 
> 
>> I've been looking at some Fluke current clamps for use with
>> oscilloscopes. These output typically 1mV/1A and have a BNC
>> connector. With a banana adapter it can be used with a DMM.
>>
>> I looked at the specs for a couple of these clamps (i410, i200s) and
>> was quite surprised to see that the output impedance is spec'd at <20
>> ohms (not Kohms, or Mohms). The "load impedance" was spec'd at 1 Mohm.
>>
>> See here for the i410 & i1010 PDF user guide:
>>
>> <http://assets.fluke.com/manuals/i4101010iseng0200.pdf>
>>
>> here for the i200 & i200s PDF user guide:
>>
>> <http://assets.fluke.com/manuals/i200s___iseng0500.pdf>
>>
>> I'm confused about how these mV output clamp probes can be used to
>> obtain an accurate signal level on an oscilloscope if the output
>> impedance is not 1 Mohn (the commonly-accepted norm input for scopes).
>>
>> Fluke tech support was no help in determining if this was a misprint
>> or to even understand how such a non-standard output impedance could
>> impact measurement.
>>
>> I could go on the premise that Fluke wouldn't be selling any of these
>> "scope" type current probes if there was such an impedance mismatch,
>> but I'd really like to understand if/how well such a combination
>> works.
>>
>> Is anyone using such a probe with a scope? Is the amplitude viewed
>> correct? What model probe do you use?
>>
>> Thanks,
>> Dave
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> 
> 
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