Add resistance property.
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@ -194,19 +194,25 @@ class MAX31865:
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rtd >>= 1
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return rtd
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@property
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def resistance(self):
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"""Read the resistance of the RTD and return its value in Ohms."""
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resistance = self.read_rtd()
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resistance /= 32768
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resistance *= self.ref_resistor
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return resistance
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@property
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def temperature(self):
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"""Read the temperature of the sensor and return its value in degrees
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Celsius.
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"""
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raw_reading = self.read_rtd()
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raw_reading /= 32768
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raw_reading *= self.ref_resistor
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# This math originates from:
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# http://www.analog.com/media/en/technical-documentation/application-notes/AN709_0.pdf
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# To match the naming from the app note we tell lint to ignore the Z1-4 naming.
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# To match the naming from the app note we tell lint to ignore the Z1-4
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# naming.
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# pylint: disable=invalid-name
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raw_reading = self.resistance
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Z1 = -_RTD_A
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Z2 = _RTD_A * _RTD_A - (4 * _RTD_B)
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Z3 = (4 * _RTD_B) / self.rtd_nominal
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@ -220,10 +226,10 @@ class MAX31865:
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temp += 2.2228 * rpoly
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rpoly *= raw_reading # square
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temp += 2.5859e-3 * rpoly
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rpoly *= raw_reading # ^3
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rpoly *= raw_reading # ^3
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temp -= 4.8260e-6 * rpoly
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rpoly *= raw_reading # ^4
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rpoly *= raw_reading # ^4
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temp -= 2.8183e-8 * rpoly
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rpoly *= raw_reading # ^5
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rpoly *= raw_reading # ^5
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temp += 1.5243e-10 * rpoly
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return temp
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