LCR Meter Readings

Hi;

I think it wouldn't make any difference for resistors, since they have no capacitive or inductive reactance (don't cause current and voltage shifts at various frequencies) they're most commonly tested using DC voltage. The following is an exerpt form a BK LCR manual:

The test frequency is user selectable and can be changed. Generally, a 1 KHz test signal or higher is used to measure capacitors that are 0.01uF or smaller and a 120Hz test signal is used for capacitors that are 10uF or larger.

Typically a 1 KHz test signal or higher is used to measure inductors that are used in audio and RF (radio frequency) circuits. This is because these kinds of inductors operate at higher frequencies and require that they shall be measured at a higher frequency. Generally, inductors with inductances below 2mH should be measured at test frequency of 1 KHz or higher and inductors above 200H should be measured at 120Hz or lower.

It is best to check with the component manufacturers' data sheet to determine the best test frequency for the device.

Yahlasit

Hi

I think that it might make a difference if you are measuring wire wound resistors.

Job Thykkoottathil.

Yes, wire wound resistors do have both capacitance and inductance parasitics, as I mentioned before, just about all resistor types have significant parasitics, it all depends on the application as to whether or not they are significant.

Wire wound resistors (I presume you are talking about precisions) do have a variable amount of parasitics depending on value and bobbin type. These parasitics may or may not be a factor depending on your application. There is no rule of thumb here as the characteristics vary very widely and must be judged on a particular resistor not just assumptions. Wire wound resistors can be used in audio applications with no discernible effect depending on the resistor. In some instances, the parasitics have no significant effect up into the hundreds of KHz but very high values may have very significant effects at only a few KHz. At low values, the inductance/capacitance is swamped by the exceedingly low 'Q' of the resistor making the parasitics essentially of no consequence.

Wire wounds also has the lowest noise of any resistor type, with metal films next, progressing up through carbon film, oxides and carbon composition.

If you must use AC for measuring resistance, it depends on the characteristics you're after. While many metal film resistors do have fairly low values of parasitic capacitance and inductance, that is not true for most resistors. They have distributed parasitics which may affect circuit parameters, in which case an AC measurement is needed but the test frequency can can be as high as 1 MHz commonly, higher in a few types of testers.

A test frequency of 120Hz will provide a measurement pretty close to DC unless there is significant parasitics present. Most capacitors and inductors are measured at 1KHz for smaller values, large values are often measured at 120Hz, again, this is somewhat determined by the circuit parameters these components are going into. These are the two most common frequencies in LCR bridges or meters, your model does not have a DC function? Curious.

AC measurements of resistors tend to be less accurate than DC, but again, that depends on what you're trying to measure.

I generally recommend using a test frequency as close to the circuit's frequency as possible if accuracy of the component's AC characteristics are required, DC otherwise.

For Non-Inductive Resistors 1KH [actually @ a higher Freq ] & on general Purpose resistors even DC is acceptable.