Hi,
I'm trying to read a PT100 via a 4-20 converter but i'm getting the wrong reading.
The converter is scaled 4-20mA, 100Ohm to 198Ohm = 0 to 260 DegC.
I process the 4-20 via a 250 Ohm resistor to get 0-5V
as I see it 260 / 5 (0-5V input) = 52
B = ADC(1)* (2600+520)/4096 - 520
but to get a sensible reading I need to use 650 not 520 but I cannot calculate why??
B = ADC(1)* (2600+650)/4096 - 650
The usable range of the input is 1 - 5 Volts = 0 to 260 deg C as the converter sends out 4-mA as a minimum so I guess this is where my conversion is going wrong!
Any thoughts?