5 tips: How to monitor temperature wirelessly

Wireless devices can make temperature monitoring easier in many applications, according to Omega Engineering Inc. Today's wireless instrumentation technologies provide new ways to apply temperature measurement sensors.

05/29/2009


Stamford, CT – Wireless devices can make temperature monitoring easier in many applications, according to Omega Engineering Inc. Today’s wireless instrumentation technologies provide new ways to apply temperature measurement sensors.

Omega Engineering MWTC and UWTC Wireless Connectors with Thermocouples Attached

Omega Engineering MWTC and UWTC Wireless Connectors with Thermocouples Attached

Prior limitations and complexities of point-to-point, mechanically interconnected instrumentation systems no longer apply, the company says. 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.

1. 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.

2. For simpler one or two sensor applications
, it means installing the wireless sensor, setting up the receiver, and being done.

3. So many wireless transmitting and receiving devices are available
for temperature measurement that

nearly any application can benefit from use of wireless technologies

. Application not previously considered cost effective for measurement may be worth looking at with wireless communications. Most of the devices discussed also work with humidity and barometric pressure sensors.

4. Wireless transmitter options vary
from sensors, enclosures, and via RS-232 communications.
-Thermocouples and RTDs (resistance temperature detectors) are temperature sensors most commonly in use. 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 feet, accommodating most applications. For example, wireless thermocouple connectors from Omega Engineering accept a plug-in sensor and transmit 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 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 converts it to USB protocol for connection to a PC. The PC can communicate with the RS-232 device as if it is directly connected. This works with new installations and retrofits.
-In liquids 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.

Omega Engineering wireless receiver
Omega UWTC-REC1 Wireless 12-Channel USB Receiver

5. Wireless receivers also have advanced, bringing new capabilities for measurement and process control, via USB, in analog, and with web servers.
-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. High and low temperature alarms are indicated by a blinking red reading. 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, avoiding the need for a host computer. Such a device has its own IP address and serves web pages that display real time temperature readings and charts. It is accessed for viewing and configuration using a pc with a web browser. Access can be restricted through password protection. Additional capabilities typically include alarm notification by email or text messaging. Web-based wireless receivers allow ad hoc monitoring using a PC with an Internet connection. The design allows data to be viewed from more than one location and removes any restriction on the distance of the monitoring point or control center from the temperature sensors being monitored.
-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. Screens can show sensor readings and chart data. The screens are interactive and allow configuration programming of the receiver.
Read the Omega Engineering white paper, “ Wireless Devices Deliver Great Benefits ,” for more information about the enabling wireless devices to advance temperature measurements.
See the

Control Engineering Wireless Implementation Guide

and the System Intergration channel .

- Edited by Mark T. Hoske , editor in chief, Control Engineering News Desk, www.controleng.com

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