The JUMO Wtrans RF temperature probe, type T01.G1, for mobile or stationary measurement of temperature at movable and fixed locations, and the matching T01.EC1 multifunction receiver, were developed so that temperature measurements can be transmitted in future without needing any wiring – wireless. The transmitter is built into the probe handle, and is protected by a waterproof housing. The transmission frequencies which are used are largely insensitive to external sources of interference, and permit transmission even in tough industrial environments. The transmitter is designed as an insertion probe. The probe is available with fitting lengths from 50 to 1000 mm, and includes a platinum chip resistor as the sensing element. The transmitter can handle a temperature range from –30 to +260 °C. The permissible ambient temperature range for the eletronics is –30 to +85°C.
In order to take account of the presently applicable legislation and comply with the existing regulations and industrial standards, an RF solution was selected that uses a proprietary protocol in the ISM band on frequencies of 868MHz (Europe) or 915MHz (Australia, Canada, New Zealand, USA).
The receiver (for DIN-rail mounting) provides the measurements on four analog outputs (0(4) — 20 mA, 0 — 10 V) and via an RS485 interface that uses a Modbus protocol. Each receiver can handle up to 16 Wtrans transmitters (insertion temperature probes), through the RS485 interface.
Useful functions ensure comfortable operation and a widespread range of possible applications. System parameters can be varied and the necessary and required settings can be made through an easy-to-use setup program. Alternatively, all the functions can also be called and adjusted by means of the keys and displayed on the receiver itself. It is thus possible to set parameters such as linearization, scale start and end, filter constants, offset and drag pointer (minimum/maximum value storage) separately for each analog output. The possibility of selecting one of the above-mentioned or other parameters as the trigger for an alarm opens up a wide range of application and monitoring options for the user. All outputs on this instrument are electrically isolated. The temperature measurement is aimed at providing the real-time response of the individual measurement variables.
The implementation of a very future-oriented RF transmission technology leads to a considerable reduction in installation expenditure. Other advantages are obvious: Long connecting cables in wired systems are almost always a nuisance for the user. Here, RF-based temperature sensors offer an effective and economical alternative, compared with wired solutions. Expensive and interference-prone cable connections are eliminated, and the RF-based temperature sensor technology continues to function even in tough industrial surroundings. Costs for new installations, service and repair are reduced by comparison with cable-borne measurement data transmission. JUMO’s Wtrans wireless technology opens up fully new application areas for the transmission of temperature data.