Hi,

Does anybody know any application notes how to measure impedance with very low real part - around up to 1-2 Ohms. Something like long piece of metal ( pipe, pole ... )

Thank you

Hi,

Does anybody know any application notes how to measure impedance with very low real part - around up to 1-2 Ohms. Something like long piece of metal ( pipe, pole ... )

Thank you

I need to add to my comment above. While the ADuCM350 can measure very low impedance values, it must have at least 100Ohms in the measurement loop for stability. If the impedance that is to be measured is expected to be below this, then an additional (known) resistor should be placed in series to ensure at least 100Ohms. This resistor value can be subracted from the result. Because the measurement result is determined by a ratiometric calculation relative to RCAL, it is important that the these steps are followed:

- Convert total impedance (known + unknown) to magnitude and phase (ratiometric calculation, relative to RCAL)
- Convert back to real and imaginary
- Subtract the known resistor value from the real component
- Convert to magnitude and phase again to give the value of the unknown impedance

The ADuCM350 has a very wide impedance measurement range; from milli-ohms to mega-ohms. The AN-1271 application note explains how to optimise the AFE for a particular impedance range.