Coaxial cable for Kelvin probes?

[Emperor-TK]

Is there any reason to avoid using coaxial cable for 4-wire (Kelvin) resistance meter leads? I need to make a new test jig for work, and I've already started building it with coax, which is what I had on hand. My plan is to have the left pair of probes on one wire, and the right pair of probes on another. Would I be better off putting the current or the sensing probes on the shield?

Thanks,
Chris

 

[jdbakker]

What frequency range do you expect to see?

How much current will pass through the measurement resistor?

What kind of coax are you using? Run of the mill CableTV coax often has a steel inner conductor with a relatively thin copper cladding to save cost. That's fine for higher frequencies (tens of MHz and up) because the skin effect causes the RF current to run through the copper cladding, but at DC the steel presents a significant resistance.

JDB.

 

[Emperor-TK]

Thank JDB,

I just checked my manual. DC is used for the current source. Maximum current is 1mA. The current flowing through the DUT will be negligible due to the high impedance sense loop. I am using coaxial Pomona test leads with banana ends, so I can have the current run through either the center conductor or the shield. Intuitively, it seems like having the low impedance sensing wires on the shield would be less desirable.

-Chris

 

[Freq Band]

This is from an ESI Micro-Ohm meter.
They use a LEMO connector for convenience.

The High and Low sides each have a Voltage (V) and Current (I) wires to measure the resistance.
And each are shielded at the source only (open at the D.U.T. resistor).


I suppose you could use 2 Triax Cables..inner wire, inner shield, and outer shield (for ground/common)......or four regular coax cables (RG58 type)

The "four wire" setup is important for critical low-ohm measurements.
But for high-ohms, the shield should be connected to the test fixture's case (just always shield the case, to be safe.)

 

[Freq Band]