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发表于 2014-2-19 09:48:47
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I have done this, using one atmega32u4 and two resistors.
Connection is simple:
GPIO 1 -> resistor 1 -> dut -> resistor 2 -> GPIO2
ADC taken from both sides of the dut, in differential mode, with 200x gain.
Procedure:
1) set GPIO1 and clear GPIO2;
2) differentially measure the voltage across dut, at 200x gain;
3) clear GPIO1 and set GPIO2;
3) differentially measure the voltage across dut, at 200x gain;
The adc results in 2) - the adc results in 3) is proportional to the dut's resistance.
With calibration, it can accurately measure resistance down to mohm territory and is not susceptible to offset drift.
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