How can I plot Z for a set of chokes?

[hobbs125]

Hello everyone,

I need to find a way to measure and plot the impedance of a set of chokes across a frequency range of 10kHz. Any ideas how I can do that? I have a frequency generator, a variable power supply and an oscilloscope with a spectrum analyzer.

 

[berkeman]

Hello everyone,

I need to find a way to measure and plot the impedance of a set of chokes across a frequency range of 10kHz. Any ideas how I can do that? I have a frequency generator, a variable power supply and an oscilloscope with a spectrum analyzer.

If you just need the Z at 10kHz, then there is no frequency range involved. What is the equation for Vout/Vin for an RL circuit? How can you apply that now?

 

[hobbs125]

I want to actually measure the impedance from 30-40 kHz and plot it against the frequency.

 

[berkeman]

I want to actually measure the impedance from 30-40 kHz and plot it against the frequency.

Then just use an RL circuit. Put your oscilloscope probe #1 at the output of the signal generator before the R, and probe #2 between the R and L (far side of L goes to ground). Work out the math for the attenuation and phase shift versus frequency, to help you choose a good value of R for a given L.

 

[alphy]

There are a few different methods you can use to plot the impedance of a set of chokes. One option is to use a vector network analyzer (VNA) which is specifically designed for measuring impedance across a range of frequencies. This would provide you with precise and accurate results.

If a VNA is not available, you can use the equipment you mentioned - a frequency generator, variable power supply, and oscilloscope with a spectrum analyzer - to plot the impedance. First, you will need to set up the circuit with the chokes in series and connect it to the frequency generator. Vary the frequency of the generator and measure the voltage and current at each frequency using the oscilloscope. From these measurements, you can calculate the impedance using the formula Z=V/I, where V is the voltage and I is the current.

Once you have the impedance values at different frequencies, you can plot them on a graph using a spreadsheet software or a specialized impedance plotting software. This will give you a visual representation of the impedance across the frequency range and can help identify any patterns or trends.

It is important to note that the accuracy of your measurements will depend on the quality of your equipment and the precision of your circuit setup. It is recommended to calibrate your equipment and perform multiple measurements to ensure reliable results.

Overall, using a VNA or the equipment you have available, you can successfully plot the impedance of a set of chokes across a frequency range of 10kHz. I hope this helps and good luck with your measurements.