Using Analog Devices AD7193 4-channel sigma-delta ADC, I am getting a 5-20mV reading as soon as I connect a jumper cable to differential inputs AIN1 – AIN2 (the other end of the jumper cable is open/in the air). Without connecting any cable the reading falls to zero!
(I am using Digilent PmodAD5 board. Attached board schematic and AD7193 datasheet).
Need quick advice on properly making a reading.
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Hello, i dont have much time to help you with your problem, but i can tell you what first comes on my mind when i read your text. Your wire, if other end is in the air, can collect some noise from everywhere when its Plus
Hi, Have you configured in proper way the CONFIGURATION REGISTER of the AD7193?It looks the inputs can be also configured in pseudo differential way. Cheers Ugo Fabrizi
Hello, my friend. I am not sure if I correctly understood the problem you are reporting. It seems to me that what you observed IS the expected behavior! Your open wire is acting as an antenna or an electroscope, due t Plus
Have you checked spectrum of the signal you are getting? In normal environment, 5-20mV can be explained by induced voltage from power grid, with your ADC speed it should be easy to check. Overall, proper cable shieldin Plus
What you are doing by adding an open ended cable is effectively placing an antenna in the circuit. To get an accurate measurement the differential input requires a minimum source current.