Wireless Devices For Temperature Monitoring
Wireless Devices Deliver Great Benefits for Temperature Monitoring
Temperature is certainly among the most commonly measured parameters in industry, science, and academia. Recently, the growth of wireless instrumentation technology, along with some clever innovations, has provided new ways to apply temperature measurement sensors combined with personal computers to collect, tabulate, and analyse the data obtained. For complex, multi-sensor applications, wireless devices provide a means to eliminate the nuisance of running multiple leads over long distances through harnesses or conduit to a control room, instrument panel, or equipment rack, while keeping track of which leads are which. For simpler one or two sensor applications, it means installing the wireless sensor, setting up the receiver, and being done.
There are now so many wireless transmitting and receiving devices available for temperature measurement that nearly any application can benefit from their use. In any case, it is certainly worth a closer look. As a bonus, most of the devices shown also work with humidity and barometric pressure sensors.
The temperature sensors most commonly in use are thermocouples and Pt100 RTDs (100 ohm platinum resistance temperature detectors). The various types of transmitting units available will handle nearly any type or model, and, depending on obstructions and other factors that affect transmission, can have ranges of up to 120 metres, so there are not many applications that cannot be addressed.
The simplest transmitting devices, like the wireless thermocouple connectors shown on the left, the MWTC and UWTC (Patented by Omega Engineering, Stamford, CT), accept a plug-in sensor and transmit the data to a receiving device at programmable intervals of 5 seconds to 1 minute. Depending on this sampling rate, battery life can be a year or more. In addition to temperature readings, these units transmit battery status information which help ensure timely battery replacement and prevent unexpected sensor-down situations.
For outdoor applications or harsh environmental conditions, a wireless IP or NEMA rated transmitter, shown on the left, the UWTC-NEMA Enclosure can be used. These devices transmit the same data as those in standard enclosures, but have a much longer battery life (up to 3 years), since they may be installed in remote or difficult to access locations. A weather seal protects the internal sensor connections.
The Omega Z-Series feature attractive wall mount, battery powered transmitters with built in sensors. Models are available for Temperature, Humidity and Barometric Pressure. High power, IP rated industrial transmitters are also available.
The RS232 interface has been popular in the past for sensors with built-in electronics. However, RS232 cable lengths are limited to 15 metres. For longer runs,wireless RS232 transmitter/receiver sets like the one shown on the left, the WRS232-USB RS232 are available. The RS232 output is forwarded to the receiver, which converts it to USB protocol for connection to a PC. The PC can still communicate with the RS232 device as if it is directly connected. This type of wireless device is suitable for both new installations and retrofits.
When making measurements in liquids or corrosive environments, the thermocouple or RTD sensing device often needs to be protected. In such cases, a probe, which encloses the sensing device in a protective tube or shell, is commonly used. For these applications, a wireless sensor probe transceiver, such as UWTC-NB9, integrates the wireless transmitter with the probe in a single unit.