Microcontroller Based Lcr Meter
M ~ E S S O R S AND
MICROS~TEMS
ELSEVIER
Microprocessors and Microsystems 20 (1996) 297-301
Technical application
Microcontroller based LCR meter
M.A. Atmanand, V. Jagadeesh Kumar
Department of Electrical Engineering, Indian Institute of Technology, Madras 600 036, India Received 19 March 1995; revised 10 May 1996
Abstract
A microcontroller based scheme for LCR measurement is described. The unknown element (an inductor or a capacitor or a resistor) is measured employing a non conventional ac bridge. The element to be measured forms one arm (side) of the bridge and the second (series) arm is made up of a simple resistor. A Multiplier type Digital to Analog Converter (MDAC), controlled by a microcontroller, serves as the other two arms. The microcontroller, after obtaining quadrature condition between the bridge output and one of the designated bridge voltages, acquires the current through and voltage across the series connected resistor. With these values and the value of digital input to the MDAC, the parameters of L or C or R values are evaluated by the microcontroller and displayed in appropriate display fields. The scheme was implemented using an Inte18751 microcontroller. An overall accuracy of the order of +1.0% was achieved for the prototype with a 12-bit MDAC having an accuracy of 4-0.2%.
Keywords: LCR measurement; Microcontroller-application; Quasi-balanced bridge; PSD-application
1. Introduction
Measurement of components (inductance L, Capacitance C or resistance R) is essential in many fields of electrical and electronics engineering. Several schemes for LCR measurement have been developed for general as well as specific applications. These methods can be normally grouped into (a) bridge methods and (b) direct methods. In a class of direct methods o f measurements, a known current is passed through the unknown impedance Z (where Z could be L, C or R) and the resulting voltage across it is measured and used for computation [1,2].
MICROS~TEMS
ELSEVIER
Microprocessors and Microsystems 20 (1996) 297-301
Technical application
Microcontroller based LCR meter
M.A. Atmanand, V. Jagadeesh Kumar
Department of Electrical Engineering, Indian Institute of Technology, Madras 600 036, India Received 19 March 1995; revised 10 May 1996
Abstract
A microcontroller based scheme for LCR measurement is described. The unknown element (an inductor or a capacitor or a resistor) is measured employing a non conventional ac bridge. The element to be measured forms one arm (side) of the bridge and the second (series) arm is made up of a simple resistor. A Multiplier type Digital to Analog Converter (MDAC), controlled by a microcontroller, serves as the other two arms. The microcontroller, after obtaining quadrature condition between the bridge output and one of the designated bridge voltages, acquires the current through and voltage across the series connected resistor. With these values and the value of digital input to the MDAC, the parameters of L or C or R values are evaluated by the microcontroller and displayed in appropriate display fields. The scheme was implemented using an Inte18751 microcontroller. An overall accuracy of the order of +1.0% was achieved for the prototype with a 12-bit MDAC having an accuracy of 4-0.2%.
Keywords: LCR measurement; Microcontroller-application; Quasi-balanced bridge; PSD-application
1. Introduction
Measurement of components (inductance L, Capacitance C or resistance R) is essential in many fields of electrical and electronics engineering. Several schemes for LCR measurement have been developed for general as well as specific applications. These methods can be normally grouped into (a) bridge methods and (b) direct methods. In a class of direct methods o f measurements, a known current is passed through the unknown impedance Z (where Z could be L, C or R) and the resulting voltage across it is measured and used for computation [1,2].
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