CHART_RECORDER_RANGE_EXTENDER

Published:2009/7/16 5:41:00 Author:Jessie | From:SeekIC

The circuit diagram shown was designed to adapt a laboratory chart recorder with a 100-mV in-put for full-scale deflection so that it will accept input voltages of 1V, 2V, 5V, or 10V at the flick of a switch. The op amp (IC1) is configured as an inverting amplifier whose feedback resistance is much less than the input resistance (R1); therefore, the output voltage will be a fraction of the input signal. Range switch S1 selects among four different feedback resistors, which consist of fixed metal-film resistors and a 20-turn cermet trimmer, which is adjusted to produce 100 mV output at the selected input voltage range. In practice, VR2 should be adjusted to 100 mV output at 2V input. The other ranges are set up in the same manner.



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