T-String™ is very useful in a variety of applications, however the design was driven by the demand for economical temperature measurements in electronic equipment racks and cabinets. The spacing and length are optimized for a 1.8m rack. It will measure temperature strata from top to bottom at 30cm intervals.
The T-String™ is designed to run on the 1-Wire™ bus, and consists of 6 temperature sensors mounted in parallel, on an 2.4m cable. Each one of the DS18B20 sensors has a unique 16 digit address. One end of the cable is terminated with a male RJ45 connector. The first sensor is mounted 90cm from the RJ45 connector, with the remaining 5 sensors placed 30cm apart.
NOTE: There is a memory device (DS2431) on the cable, approximately 15cm from the RJ45 connector. The device looks exactly like the sensors - it is not a sensor. The DS2431 is used to identify the position of each sensor in the string. T-String will report the sensor closest to the RJ45 connector first and then each sensor in progression out to the end of the string.
The high temperature range of the T-String is limited by the PVC coating on the cable. The rated temperature for the PVC sheathing is 60 C. The approximate response and recovery times of the DS18B20 sensors can be seen in appendix 1 of the T-Sense manual. The cable is 1 pair cat5E construction, with pins 1 and 3 of the DS18B20 sensor tied together forming the ground, or return, line. Pin 2, the data line is brought directly to the connector.
Each sensor is mounted on a small printed circuit board and enclosed by our low pressure molding process. The upper half of the DS18B20 sensor is not molded, allowing response times that are very close to a bare sensor. The benefits of the molding process are: Very small cross sectional dimension permits minimal resistance to air flow; No conductive surfaces are exposed; Provides excellent strain relief on all connections; Highly weather resistant and, though it has not been tested, it is likely to be water proof.
There are no other devices involved in the circuitry, so the basic operating specifications of the DS18B20 are valid for T-String. Briefly stated, the specifications are: Temperatures from –55°C to +125°C (–67°F to +257°F); ±0.5°C accuracy from –10°C to +85°C.