- Fri Feb 24, 2012 9:03 am
#140271
Hello.
I am using an external ADC (MCP3421), 16-bit resolution, with internal PGA (internal gain) of 8x to read signals from a thermocouple type T. Within my current ADC configuration, the differential input impedance is around 280K.
But when the inputs are floating, the result of ADC conversions behaves incorrectly (negative and positive aleatory values, sometimes with high values are read from ADC).
I want this ADC to output conversion values near to zero when the inputs are floating, to detect a sensor fault, or sensor disconnected, for example.
How could I do a "pull down" to it? because the Vin- input (reference) and Vin+ input (input signal) from the ADC and and the digital ground of the IC are not in the same voltage reference.
I am using an external ADC (MCP3421), 16-bit resolution, with internal PGA (internal gain) of 8x to read signals from a thermocouple type T. Within my current ADC configuration, the differential input impedance is around 280K.
But when the inputs are floating, the result of ADC conversions behaves incorrectly (negative and positive aleatory values, sometimes with high values are read from ADC).
I want this ADC to output conversion values near to zero when the inputs are floating, to detect a sensor fault, or sensor disconnected, for example.
How could I do a "pull down" to it? because the Vin- input (reference) and Vin+ input (input signal) from the ADC and and the digital ground of the IC are not in the same voltage reference.