Hi,
Is it possible to measure low DC current with Lock -in amplifier. I do not have Source-meter, but have SRS 510 lock-in amplifier. I want I-V response of my device....
Please respond..
Hi,
Lock-in amplifiers can be used to measure modulated (AC) signals, so the answer is not. But the SR 510 has a few analogue inputs at its backplate, you can use them if you can convert the current into voltage and amplify it.
Or you can multiply your signal with a square wave using some analogue IC such as AD633, and this way you can use the SRS510 as a lock-in.
David
How small is the DC current? Be careful that when you connect additional circuitry to your device to measure this current it does not produce errors i.e. leakage currents. Currents below a nanoAmp require special techniques to measure.
Hi Avishek, I see the problem. You can try switching the current with a semiconductor like a FET but I think the charge injection from gate to substrate will be an issue. If the FET has 1 pF gate channel capacitance then chopping at 1 kHz will inject the same current as you are trying to measure. So a mechanical chopper like a reed relay may work better. Make sure the coil is fully electrostatically shielded to minimise pick up. Ensure also that all the low current connections are guarded - that is they are surrounded by low impedance conductors of exactly the same voltage as the device you're measuring so you minimise leakage. Good luck with your research!
Hi Avishek,
The MFLI lock-in amplifier DC - 500 kHz is able to measure DC signals. This instrument is also capable to measure voltage and current simultaneously. This also allows you to use the lock-in amplifier as LCR meter or impedance analyzer with some additional options. If you have more questions, please let me know.
Hi Marco,
That sounds pretty good. However, I have managed to solve that issue with an analog multiplier and SR510 LIA.
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