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ADS1194: Wrong test signal in custom PCB

Part Number: ADS1194

Hello, i bought an ECG 2 click board where the test signal looks ok, after that i made a custom PCB with the only diference that now AVDD = 3.3V, i tried the test signals in two of these custom boards and the signal have a big offset, you can see it in the images.

Why is this happening? The adquisition code and the configuration is the same in the two projects.

Test signal amplitude: 1mV

Test signal in custom PCB

Test signal in ECG 2 click

Registers Custom board                                                             Register ECG 2 click

  • Hello,

    In general, offset voltage is expected to vary within a certain range from channel to channel. For the ADS1194 device, you can typically expect between +/-500 uV of offset error, and about 2 uV/deg(C) of drift, according to the datasheet.

    You may want to examine the offset error of the channels with the inputs shorted together.

    Also noticed that the channel configuration are different between the custom board and ecg 2 click board.

    Additionally there are 2 bits in CONFIG2 and CONFIG3 register that must be set to 1 after power up.