0 Ohms and -224.020C from MAX31865

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Spudcrazy
 
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Joined: Sun Mar 05, 2023 9:21 pm

0 Ohms and -224.020C from MAX31865

Post by Spudcrazy »

Hi! I have been struggling to get the adafruit MAX31865 PT1000 amplifier to work. I have looked at many previous posts and checked their suggestions - double-checked the wiring, measured the resistance of the RTD w/ a multimeter. Also checked all of my connections w/ the multimeter to see if solder joints are intact. I have bought another MAX and swapped it in, same results, so I do not think it is the hardware. The software is tricky though: I am running a Raspbian OS on a Libre Le Potato, their distribution meant to work on their hardware, and I use the Libretech wiring tool to get the overlays to work. If I purposefully miswire the MAX, I can get it to read the resistance of the reference resistor (about 4300 Ohms and 988.7C) - if i swap out SPI wires, if I change the CS pin. So I can "control" the outcome to a certain extent, but I cannot get it to read the real resistance. I am using a 3-wire PT1000 also purchased from Adafruit. Pics of setup below, as is code. Powered at 3.3V.

Code: Select all

#import time
#import gpiod
import digitalio
import adafruit_max31865
import board
#import sys

spi = board.SPI()
cs = digitalio.DigitalInOut(board.P26) # Chip select of the MAX31865 board.
sensor = adafruit_max31865.MAX31865(spi, cs, wires=3, rtd_nominal=1000.0,
ref_resistor=4300.0)

print('Temperature: {0:0.3f}C'.format(sensor.temperature))
print('Resistance: {0:0.3f} Ohms'.format(sensor.resistance))
Adafruit order #: #3001187-3330027055
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