FWIW
This is the 100k thermistor code I use for a multichannel PID 3d printer bed . The multiple channels are externally multiplexed into a single PICO ADC channel the set_filter() function is called from a 40mS timer.
The polynomial gives a wide range accurate result in less than 500uS. The 4th order coefficients are obtained by plotting the thermistor response v. temperature entering the data into a libre-calc spreadsheet and using the trend command to get a good fit
This is the 100k thermistor code I use for a multichannel PID 3d printer bed . The multiple channels are externally multiplexed into a single PICO ADC channel the set_filter() function is called from a 40mS timer.
The polynomial gives a wide range accurate result in less than 500uS. The 4th order coefficients are obtained by plotting the thermistor response v. temperature entering the data into a libre-calc spreadsheet and using the trend command to get a good fit
Code:
class Sensor(object): def __init__(self, Channel, Ave=10): #print(f"sensor{Channel} initialised") self.adc0 =ADC(0) self.CH = Channel self.Filter=[] self.Ave = Ave def VT(self,X): '''convert ADC Value to temp in °C''' #4th order polynomial X2 = X * X X3 = X2 * X X4 = X3 * X T0 = (5.425E-16 * X4) T1 = (6.485E-11 * X3) T2= (2.895E-06 *X2) T3 = (0.0548 * X) return -T0+T1-T2+T3 - 273 def set_filter(self): self.Filter.append(self.adc0.read_u16()) if len(self.Filter) >self.Ave : self.Filter.pop(0) def get_value(self): Mtot=0 for M in self.Filter: Mtot += M return self.VT(Mtot//self.Ave) Statistics: Posted by BillTodd — Wed Jan 24, 2024 7:18 pm