CURRENT_CONVERTER

Published:2009/6/30 3:14:00 Author:May | From:SeekIC

Converts 8-bit TTL digital inputs to process current in range of 4 to 20mA, for microprocessor control of industrial operations. Fixed 0.5-mA current is added to DAC output current varying between0 and 2.0 mA and multiplied by factor of 8 to produce final output current of 4-20 mA. To calibrate, connect ammeter between output and ground, then apply +23 V ± 7 V and －5 V ± 1 V to converter. Make digital inputs all 0s (less than +0.8 V). Adjust R1 until output current is 4.0 mA.Changedigital inputs to all is (greater than +2.0 V), and adjust R2 until output current is 20 mA.—D. Soderquist, Build Your Own 4-20 mA Digital to Analog Converter, Instruments & Control Systems, March 1977, p 57-58.



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