nest.class.php
public function getDeviceTemperatureScale($serial_number = NULL) {
        $serial_number = $this->getDefaultSerial($serial_number);
        return $this->last_status->device->{$serial_number}->temperature_scale;
    }
public function getDeviceTemperatureScale($serial_number = NULL) {
        $serial_number = $this->getDefaultSerial($serial_number);
        return $this->last_status->device->{$serial_number}->temperature_scale;
    }
Get the thermostat preferred scale: Celsius or Fahrenheit.

@param string $serial_number The thermostat serial number. Defaults to the first device of the account.

@return string 'F' or 'C'