The WattNode® BACnet® WattNode offers temperature measurement using an external thermistor when ordered with Option TM1. This article describes the specifications for the temperature measurement and the associated thermistor.
For more details, see the WattNode BACnet reference manual:
- Firmware Versions 1.20 and 1.13: Reference Manual (PDF, 57 pages)
- Thermistor Connection: The thermistor is connected between the X and C pins on the four-position black screw terminal. The connection is polarity insensitive.
- Temperature Accuracy: ±3°C, not including thermistor errors
- Temperature Resolution: better than 1°C from -50°C to 150°C
- Response Time: <= 2 seconds (not including thermistor response time)
- Temperature Measurement Range: -50°C to 150°C
- Thermistor Specifications:
- Type: Designed for standard 10k ohm thermistors. Contact CCS for other thermistor types.
- Curve: Designed for US Sensor curve J thermistors. Can support other thermistor curves by programming the thermistor coefficients (see below) or contact CCS for pre-programmed support.
- Firmware Information
- Version: 1.20
- Temperature Analog Value Object: Added ThermistorTemp (object number = 58) temperature analog input object to report the measured temperature in degrees Celsius.
- Thermistor Configuration Objects: Added ThermistorCoeffA, ThermistorCoeffB, and ThermistorCoeffC analog value objects the thermistor Steinhart-Hart coefficients.
- BTL: The firmware for the WattNode BACnet with option TM1 (thermistor input) is not BTL (BACnet Testing Laboratories) certified. However, it is based on a firmware version that is BTL certified and has been tested by CCS with the VTS test suite.