Roy, A. and Sharma, Lakhi and Chakraborty, I. and Panja, S. and Ojha, V.N. and De, S. (2019) An FPGA based all-in-one function generator, lock-in amplifier and auto-relockable PID system. Journal of Instrumentation, 14. P05012-P05028. ISSN 1748-0221

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Abstract

We report an all-in-onewaveformgenerator, lock-in amplifier and Proportional-Integral-Differential (PID) controller, embedded in a single Field Programmable Gate Array (FPGA). The PID controller is advanced with a novel automatic relocking mechanism, which is capable of self-finding and relocking at the desired setpoint upon unlocking of the PID due to disturbances. The instrument is designed in such a way that these devices can either be used individually or simultaneously. Digital implementation via software processing of the associated modules is used and the firmware is embedded in an FPGA IC, which makes it compact and reconfigurable. The instrument consists of a hardware for establishing external linkage and a Python based computer-controlled interface to control it from a remote PC as well as for acquiring and plotting relevant data. A steep roll-off of the filters (6 dB/octave to 24 dB/octave), low noise density (30 nV/root Hz @ 100 kHz) in the lock-in amplifier and a PID bandwidth of 100 kHz makes it useful for wide range of applications. Versatility of the instrument is demonstrated in three different experiments, (i) Auger electron spectroscopy, (ii) low coherence optical tomography and (iii) laser frequency stabilization followed by self identification of the setpoint upon unlocking and automatic relocking to that.

Item Type:	Article
Additional Information:	Copyright for this article belongs to M/s IOP Publishing.
Subjects:	Instruments/ Instrumentation
Divisions:	UNSPECIFIED
Depositing User:	Mr. Yogesh Joshi
Date Deposited:	29 Jan 2020 11:33
Last Modified:	29 Jan 2020 11:33
URI:	http://npl.csircentral.net/id/eprint/4105

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