Title: Enhanced Howland-based constant current source for soil EC_a measurement

Authors: Ritula Thakur; Babankumar S. Bansod

Addresses: National Institute of Technical Teachers Training and Research, Chandigarh, 160019, India ' Central Scientific Instruments Organisation, Chandigarh, 160030, India

Abstract: In the present work, enhanced Howland current source-based voltage controlled current source (VCCS), used in four probe Wenner array technique to measure apparent electrical conductivity (EC_a) of soil is reported. The distortion in the output signal is negligible and current is maintained constant. To check circuit reliability for constant current characteristics across varying standard load resistance, voltages were measured to calculate value of current, which was then compared with theoretically calculated value. The performance of proposed circuit was studied using TINA-TI software simulations and it was found that proposed source is capable of providing a constant current over the entire range of resistance (0.5 Ω to 20 kΩ) within very low frequency range; with an error less than 5%, and an average error of 0.9466%, which is within acceptable tolerance in present application.

Keywords: enhanced Howland-based current source; voltage controlled current source; VCCS; Wenner array; soil electrical conductivity; EC_a.

DOI: 10.1504/IJIT.2018.090879

International Journal of Instrumentation Technology, 2018 Vol.2 No.1, pp.78 - 89

Received: 06 Jul 2017
Accepted: 10 Jan 2018
Published online: 30 Mar 2018 *