A low cost versatile differential preamplifier for electronic engineering

Abstract

Acquisition of differential signals from low voltage and high impedance sources is difficult when using commonly available laboratory test equipment such as a standard oscilloscope or single ended acquisition system. This paper presents a versatile differential preamplifier for universal signal conditioning. The probe offers a wide input voltage range and can measure signals ranging from a few hundred micro-volts up to 100 V with 1 MHz bandwidth. It also contains a programmable output filter for bandwidth limitation and noise reduction, user-accessible controls for offset adjustment and input coupling mode selection. The probe can be powered through an USB port or by using an internal battery. Input impedance can be made virtually infinite by the JFET input stage, which makes this differential preamplifier usable with a variety of high-impedance sources commonly encountered in the sensors research field and in electronic engineering. Experimental validation shows that the proposed device has better performance levels and interoperability than commercially available instrumentation at a reduced cost, even while using off-the-shelf components.

Loading-Effects Reduction Using a Voltmeter in Series and an Ammeter in Parallel

“…According to (5) and unlike (3), for a given value of R s , the higher the value of R 1 || R 2 , the lower the error.…”

“…In the testing/calibration phase of a circuit, it is essential to measure how much is the DC voltage (or current) at some critical nodes (paths) [5]. Typically, a DMM acting as a voltmeter (ammeter) is connected in parallel (series) to perform the voltage (current) measurement.…”