Bit 7 of the Configuration register (00h) enables/disables VBIAS. Upon powerup, this bit is set to 0 and the bias output is disabled. It needs to be set to 1 to enable the output.
MAX31865
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The MAX31865 is an easy-to-use resistance-to-digital converter optimized for platinum resistance temperature detectors (RTDs). An external resistor sets...
Datasheet
MAX31865 on Analog.com
Bit 7 of the Configuration register (00h) enables/disables VBIAS. Upon powerup, this bit is set to 0 and the bias output is disabled. It needs to be set to 1 to enable the output.