From d6213b35b48f3c9c0b8564ace2710451673dc1ab Mon Sep 17 00:00:00 2001 From: Tony DiCola Date: Fri, 15 Dec 2017 15:15:23 -0800 Subject: [PATCH] Add resistance property. --- adafruit_max31865.py | 22 ++++++++++++++-------- 1 file changed, 14 insertions(+), 8 deletions(-) diff --git a/adafruit_max31865.py b/adafruit_max31865.py index 63d0722..7c1f56a 100644 --- a/adafruit_max31865.py +++ b/adafruit_max31865.py @@ -194,19 +194,25 @@ class MAX31865: rtd >>= 1 return rtd + @property + def resistance(self): + """Read the resistance of the RTD and return its value in Ohms.""" + resistance = self.read_rtd() + resistance /= 32768 + resistance *= self.ref_resistor + return resistance + @property def temperature(self): """Read the temperature of the sensor and return its value in degrees Celsius. """ - raw_reading = self.read_rtd() - raw_reading /= 32768 - raw_reading *= self.ref_resistor - # This math originates from: # http://www.analog.com/media/en/technical-documentation/application-notes/AN709_0.pdf - # To match the naming from the app note we tell lint to ignore the Z1-4 naming. + # To match the naming from the app note we tell lint to ignore the Z1-4 + # naming. # pylint: disable=invalid-name + raw_reading = self.resistance Z1 = -_RTD_A Z2 = _RTD_A * _RTD_A - (4 * _RTD_B) Z3 = (4 * _RTD_B) / self.rtd_nominal @@ -220,10 +226,10 @@ class MAX31865: temp += 2.2228 * rpoly rpoly *= raw_reading # square temp += 2.5859e-3 * rpoly - rpoly *= raw_reading # ^3 + rpoly *= raw_reading # ^3 temp -= 4.8260e-6 * rpoly - rpoly *= raw_reading # ^4 + rpoly *= raw_reading # ^4 temp -= 2.8183e-8 * rpoly - rpoly *= raw_reading # ^5 + rpoly *= raw_reading # ^5 temp += 1.5243e-10 * rpoly return temp