5 tips for monitoring temperature wirelessly
Today’s wireless instrumentation technologies provide new ways to apply temperature measurement sensors. Prior limitations and complexities of point-to-point, mechanically interconnected instrumentation systems no longer apply, according to Omega Engineering. With wireless connections, control can be centralized or decentralized and data can be collected and analyzed in real time or later...
By Control Engineering Staff
Today’s wireless instrumentation technologies provide new ways to apply temperature measurement sensors. Prior limitations and complexities of point-to-point, mechanically interconnected instrumentation systems no longer apply, according to Omega Engineering. With wireless connections, control can be centralized or decentralized and data can be collected and analyzed in real time or later with PCs.
Five tips for wireless temperature measurement follow from Omega Engineering.
For complex, multi-sensor applications, wireless devices provide a means to eliminate 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.
So many wireless transmitting and receiving devices are available for temperature measurement that nearly any application can benefit from use of wireless technologies. Applications not previously considered cost effective for measurement may be worth looking at with wireless communications.
Wireless transmitter options vary from sensors, enclosures, and via RS-232 communications. For example:
• Thermocouples and RTDs (resistance temperature detectors) are the most common temperature sensors. Various types of transmitting units can handle nearly any type or model and, depending on obstructions and other factors that affect transmission, can have ranges of up to 400 ft, accommodating most applications. Wireless thermocouple connectors from Omega Engineering, for instance, accept a plug-in sensor and transmit data to a receiving device at programmable intervals of 5 seconds to 1 minute.
• For outdoor applications or harsh environmental conditions, a wireless NEMA transmitter can transmit the same data as those in standard enclosures and have a much longer battery life (up to 3 years). They may be installed in remote or difficult to access locations.
• RS-232 interface are popular for sensors with built-in electronics, but cable lengths are limited to 50 ft. For longer runs, wireless RS-232 transmitter/receiver sets can forward the output to the receiver to convert it to USB protocol for connection to a PC.
• In liquid or corrosive environments, the thermocouple or RTD sensing device often needs to be protected. A probe often encloses the sensing device in a protective tube or shell and also can contain a wireless sensor probe transceiver.
Wireless receivers now also offer new capabilities for measurement and process control, via USB, in analog and with Web servers, such as:
• The most common receivers connect to a PC through a USB port. An example is the 12-channel wireless USB receiver from Omega Engineering with accompanying software that displays readings from each channel, sensor type, sensor designator or description, ambient temperature, units, signal strength, and battery condition. Data can be saved to a file for charting and analysis.
• When an analog signal is necessary to provide process feedback to a controller or PLC, receivers that include an analog output for one channel are available. A display can be added to show this reading on the unit; it also will be displayed on the computer screen. Receivers in NEMA-rated enclosures also are available for outdoor applications or harsher indoor settings.
• New receivers are built with embedded Web servers and connect directly to an Ethernet network or to the Internet with a standard RJ45 jack. Such a device has its own IP address and serves Web pages that display real-time temperature readings and charts.
• A wireless panel meter can allow remote monitoring and local access for the machine or process operator. Such a Web-based receiver and wireless scanner can display eight sensors’ outputs. It adds local machine or process control capability by means of relay contacts and voltage output signals. The screens are interactive and allow configuration programming of the receiver.