Posted Mon, 21 Aug 2023 13:42:56 GMT by Lecor, Alioune


I am currently a student working on a project involving the characterization of piezoelectric materials. My goal is to simultaneously acquire both voltage and current data from piezoelectric films. To achieve this, I am using a machine that applies mechanical deformation to my piezoelectric films at a frequency of 5 Hz. When this stress is applied, the films generate a certain voltage, which I acquire using a DAC acquisition device, along with a current, which I measure using a KEITHLEY 6485 picoammeter. I aim to visualize this data using LabVIEW.

However, I am facing two major challenges in executing this project.

1. **Electronic Circuit for Current and Voltage Measurement:** I am seeking to design an electronic circuit that allows me to measure current in a closed circuit and voltage in an open circuit, while adhering to the specifications of the KEITHLEY 6485 picoammeter. I am wondering about the best practices to follow in designing this circuit while respecting measurement standards and device limitations.

2. **Incorrect Current Measurements:** When I attempted to measure the current using the picoammeter, connecting it to LabVIEW via GPIB and the RG50 probe, I obtained excessively high current values. These measurements do not align at all with the data specified in the datasheet of the piezoelectric material (PVDF) I am studying. This is concerning to me as I do not understand why these values are so far from expectations.

I want to emphasize that I am relatively new to electronics, and these issues seem complex to resolve. Time is of the essence as I have less than a month to complete this project. I am therefore seeking your expertise to help overcome these obstacles. Any guidance, technical explanations, or practical advice you can provide would be greatly appreciated.

I sincerely thank you for your attention to my situation and for any assistance you can offer. Your contribution will be crucial to the success of my project.

Best regards,
Posted Sat, 30 Sep 2023 12:14:30 GMT by C, Andrea
For your incorrect current measurement, try some manual operation and progressively add cable and probes.
So how low are measurements of current for just instrument?
If nice and small, restore zero check and modify connection to just one cable or connector.
Then measure again.

Some BNC cables can give quite a lot of “popcorn” spurious current noise.  Make sure you don’t have that before measuring the sample.

Is your piezo material in a shielded enclosure?  If not, then I image you will get a lot of measurable change just due to environment.  Wave your hands or walk by while measuring.  You can probably detect the motion as charged dust from air impacts the sample surface.

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