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Hello,
I am doing research that is looking at measuring extremely small displacements with a capacitive probe.
Currently we are using an HPT-75E-A-L2-5-B-D probe attached to a Capacitec Pre-amplifier (part #: 210-SLC-200HZ-BNC-ENC) through a coaxial connection. I believe the output of the pre-amplifier is a single channel that was originally going to an NI USB 6009 DAQ.
An issue arose where there was a significant amount of noise at 0.1-0.2mv and we would like to amplify this noise to 1mv.
I was wondering what would be the best chip-based approach to this problem, and if there is an entirely different product that could help that would be acceptable as well. I would the INA model chips through some brief research online and do not know how to narrow down my selection from there. Any help is appreciated.
Thank You
- Cam
Hi Cam,
Upon reviewing the Capacitec probe and pre-amp specifications it does appear that any alternate input amplifier needs to have low-noise and very high input impedance. Even though the INA103 has very low noise, its input bias current is high (microamps) which is high compared to most other instrumentation amplifiers.
The INA111 is a JFET input instrumentation amplifier with low noise and low input bias current, typically +/-2 pA. That might be a better option.
Regards, Thomas
Precision Amplifiers Applications Engineering
Hello Thomas,
Thank you for looking into the problem and making a suggestion. After looking at the data sheet for this unit I have another question. Is there a significant difference between the INA111AP, AU and the INA111BP, BU? If so, which of the two would be best for my application?
- Cam
Hi Cam,
The differences between the INA111BU/INA111BP and the INA111AU/INA111AP are the electrical parameteric performances are higher for the B-grade product i.e some inherent errors are lower for the B-grade product compared to the A-grade product. The differences occur with the Voltage Offset (RTI), Voltage Offset Drift, Gain Accuracy and Nonlinearity - all being lower for the B-grade devices. The Electrical Specifications table in the INA111 datasheet lists each of these parameters side-by-side and you can compare the numbers. It comes down to the levels of performance required for the application.
The "U" and "P" designations in the part numbers indicate the 16-pin surface mount SOL-16 and through-hole 8-pin DIP packages, respectively.
Regards, Thomas
Precision Amplifiers Applications Engineering