PCSGU250 for impedance spectroscopy

Instruments PC Oscilloscopes and Recorders
1

Dear Sirs,
several months ago I bought your product PCSGU250 with a hope to use it for impedance spectroscopy. Unfortunately, still I am not able to measure adequately a simple circuit of parallel RC and second resistor connected with them in series. I will be very grateful if you can give me a proper advice.

Thank you in advance!

2

What exactly would you like to measure?

3

I would like to measure the impedance of a simple circuit consisting of parallel R and C and second resistor connected with them in series.

4

Please note that an oscilloscope is a Voltmeter, so it has been designed to measure a voltage, not impedance.
Maybe you can calculate the impedance of your circuit by applying an AC voltage with a known amplitude and frequency, and then you can measure the difference to calculate the impedance.

5

Please note that I have bought the model with a Bode option.

6

The bode option will give you a frequency response plot of your circuit, not the impedance.
you will still need to calculate it.

7

It seems that with some special arrangements the Bode Plotter of the PCSGU250 can be used also for the impedance measurement.
Here an example:
I connected 1K resistor in series with 0.1uF capacitor and tried to measure the impedance of this network.
I connected 100k resistor in series with the network and fed 3Vrms to the circuit.

Here are the frequency and phase plots:

pcsgu211.png740×495

At 1 kHz the amplitude seems to be 0.06V.
This indicates the Z of the series connected capacitor and resistor circuit is 100k*0.06/3=2k.
The phase at 1 kHz seems to be -58.8 degrees.
These values represent the impedance of the network quite well in polar form.

8

Simulation of the impedance behavior (in the form of Nyquist plot) of circuit comprising parallel and series resistances and capacitances (Rp = 30kΩ, Cp = 50nF, Rs = 100kΩ, Cs = 1µF), obtained with the program ZView2.

Bode plot of the same simulation.

Please try to make real measurement of this scheme.

9

Dear Kochev,

Had you have any luck with the impedance spectroscopy and did you have any sense in results?. In the mean time, could you please let me know how do you configure the Zview2 simulation?. Is the simulation somehow taken any data from the PCSGU250?. Do you need to install the Zplot as well?

Best Regards

Patty

10

There is no progress with your device. Zview2 simulations of course have nothing in common with PCSGU250, Zplot is not necessary at all. Unfortunately, in my opinion the problem is in the hardware, namely PCSGU250 has very low input impedance