Why LCR Meter has tes frequency for resistance measurement?

[dknguyen]

I was using the Agilent U1733C LCR meter and was wondering why meaning there is for the test frequency selection when doing resistance measurements. It affects the reading and I have no idea why you would use anything but DC to measure a resistance.

 

[ronsimpson]

The meter has the ability to measure at different frequencies for L and C so why not R?

A resistor is not perfect. Depending on how it is made and what resistance it will not have the same reading at all frequencies.
Wire wound resistors are real bad, they have inductance. Spiral cut resistors also have some problems with inductance.
I think 10,000,000 resistors are not good at high frequencies.

 

[dknguyen]

But wouldn't measuring a resistor at anything but DC start to give you impedance rather than resistance? The meter has a separate impedance reading.

 

[ronsimpson]

You would thing that resistance or impedance at DC and 60hz will be the same for a resistor.
Win I was building 100mhz video amplifiers we used special non inductive power resistors.
In microwave amplifiers we had to look up the impedance for the resistors.

 

[dknguyen]

You would thing that resistance or impedance at DC and 60hz will be the same for a resistor.
Win I was building 100mhz video amplifiers we used special non inductive power resistors.
In microwave amplifiers we had to look up the impedance for the resistors.

Well the issue is that the LCR meters seems incapable of reading resistance at DC at all. We're stuck measuring only 100Hz and up.

 

[crutschow]

If it's a wire wound resistor, the skin effect may cause the real resistance to got up with frequency.
That is unrelated to any increase in reactance due to its inductance.

 

[ronsimpson]

Well the issue is that the LCR meters seems incapable of reading resistance at DC at all.

broken meter??

 

[dknguyen]

broken meter??

no, absent feature

 

[Wade Hassler]

Page 39 of the User's Guide shows how DC resistance measurements are done

 

[dknguyen]

Page 39 of the User's Guide shows how DC resistance measurements are done

Ah, great thanks.