Analog Scaling
The analog temperature sensor has no software requirements other than configuring the connecting devices analog gain and offset.
The sensor is based on a TI TMP235 temperature sensor and has a gain and offset of:
| gain (\(T_{c}\)) | 10mV/degC |
| offset (\(V_{0}\)) | 500mV (at 0degC) |
It is straightforward to convert this for use on JCS devices:
The temperature sensor has the transfer function \(V_{o} = T_{A} \times T_{c} + V_{0}\).
Here \(V_{o}\) is the sensor output voltage, \(T_{A}\) is the measured ambient temperature and \(T_{c}\) and \(V_{0}\) are the scale and offset from above.
The sensor transfer function is rearranged to solve for the ambient temperature:
Most JCS devices that accept the analog temperature sensor have a 3.3V reference and a 12bit ADC, therefore scaling from ADC counts to Volts is given by \(V_{o} = \left({3.3\over{4096}}\right)\times adc_{counts}\).
The analog sensor temperature is then be given by the formula:
Substituting values in gives:
JCS device requires the analog gain and offset in the form \(V_{o} = gain \times adc_{counts} - offset\). Here we can simply extract the analog interface gain and offset terms for the device configuration:
an_0_gain: 0.0805664063
an_0_offset: 50.0