T-String
Maker : iButton Link
Although the design was driven by the demand for economical temperature measurements in electronic equipment racks and cabinets, the T-String can be used in many different ways. The spacing and length are perfect for a 72” rack. It will measure temperature layers from top to bottom at 1 ft intervals.
The T-String is designed to run on a 1-Wire® bus. The T-String itself is made up of six sensors mounted on an 8 ft cable. Each of the DS18B20 sensors has a unique 6-digit address. One end of the cable has a male RJ-45 connector with the first sensor mounted three feet away from the connector. The other five sensors are placed 1 ft apart.
There is also a DS2431 memory device on the cable approximately 6 inches from the RJ-45 connector. This is used to identify the position of each sensor on the string, and looks exactly like the sensors. It is NOT a sensor. The T-String will report the sensor closest to the RJ-45 connector first, and then each sensor following it to the end of the string.
The PVC coating on the cable slightly decreases the reading abilities of the sensor. The rated temperature for the PVC coating is 60°C (140°F). The cable is 1 pair cat 5E constructions, with pins one and three of the DS18B20 sensor tied together to form the ground/return line. Pin two is the data line and is brought directly to the connector. Approximate response and recovery times of the DS18B20 sensors can be found in Appendix One of the T-Sense manual.
Each sensor is mounted on a small circuit board and covered by our low-pressure molding process. The upper half of the DS18B20 sensor is not molded, which allows for response times very close to the response times of a bare sensor. This molding process has many benefits. The very small cross-sectional dimension permits minimal resistance to airflow. There are no conductive surfaces exposed and there is excellent strain relief on all of the connections. Additionally, the molding process makes the sensors highly weather resistant, and, although it has not been tested, potentially waterproof.
The circuitry has no other devices involved in it, so the basic operating specifications for the DS18B20 also apply to the T-String. Those specifications cover temperatures -55°C to +125°C (-67°F to +257°F). There is ±0.5°C accuracy -10°C to +85°C.
Custom T-Strings can be ordered, allowing for customization of over-all length, spacing between sensors, and number of sensors (up to 15). A minimum order of 10 T-Strings is required. The price will be quoted as “Special.”