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Wireless Technology Choices For Temperature Monitoring Sensors - Part 2

Apr 01, 2014
WTM device claims about Transmission Range need closer scrutiny.

Part 1 of this title examined data rate factors in selecting Wireless Temperature Monitor devices from the graphic below. Essentially, data rate is not ever a factor since the monitoring interval for medical refrigeration WTM devices is in the order of minutes and produces very small amounts of data. The only time data rate could be a factor is if the refrigerator is monitored every second or less and a number of additional parameters was being transmitted, however even this would not be a factor in many cases since, again, the amount of data is small. There may be a case where rate is a factor if, for example, high definition video transmission was added to the data. Since such systems when in use are generally part of the facility’s security systems, data rate should not be concern when evaluating WTM devices for hospital refrigeration monitoring.

Comparison of range vs. peak data rate for wireless communication technologies used in Wireless Temperature Monitoring (WTM) devices. (Link to Source)

Range, unlike data rate is a factor that needs to be understood when making a WTM system selection. This is for several reasons. First, wireless technology included a wireless transmitter and the transmitted data needs to be able to reach the corresponding wireless receiver, either the facility’s wireless network or a dedicated device provided by the supplier. In some cases where several wireless temperature sensors are communicating with a single receiver, even more care is needed to insure robust communication.

Another factor inherent in range but not generally acknowledged is interference from the facility itself. Factors such as walls, medical or infrastructure equipment, furniture and file cabinets and in cases where the WTM device is entirely inside the refrigerator, the refrigerator itself. Claims about range are almost always based on optimal conditions: line of sight in air. Qualifiers that the WTM device’s range may vary depending on interference from objects in the immediate vicinity are offered. (Full disclosure: Temperature@lert offers both a Line of Sight and Indoor/Urban specification for its wireless devices.) These are reasonable qualifiers.

The table below provides another view of the presentation in the graphic above. In the Range row wireless options are generally noted as a range, 10 to 100 meters in the case of WiFi, for example. Those who use WiFi networks and portable devices in their homes or work can attest to the variability of signal strength as they move away from the WiFi router (transmitter/receiver) or move into an area that is heavily furnished or shielded by a number of walls between the portable device and the WiFi router.

Comparison of Wireless Networking Technologies used in WTM Systems. (Link to Source)

Because range is such an important but difficult to absolutely specify parameter when choosing a wireless temperature monitor experimentation with a test device from the WTM supplier is recommended. A single device is usually sufficient since it can be moved around the facility to determine the suitability in different locations and under different conditions. Recording the results for a few minutes at each location is all that is needed since the signal is either there or not there, and the data stream is either coherent or not. Again, experience with home WiFi networks are instructive.

The next piece in this series will examine a WTM device parameter closely tied to data rate and range, power source type and the effects on performance.

Temperature@ert’s WiFi, Cellular and ZPoint product offerings linked to the company’s Sensor Cloud platform provides a cost effective solution for organizations of all sizes. The products and services can help bring a laboratory or medical practice into compliance with minimum training or effort. For information about Temperature@lert visit our website at or call us at +1-866-524-3540.

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Written By:

Dave Ruede, Well-Versed Wordsmith

Dave Ruede, a dyed in the wool Connecticut Yankee, has been involved with high tech companies for the past three decades. His background in chemistry and experience in a multitude of industries such as industrial chemicals and systems, pulp and paper, semiconductor fabrication, data centers, and test and assembly facilities informs his work daily. Well-versed in sales, marketing, management, and business development, Dave brings real world experience to Temperature@lert. When not crafting new Temperature@lert projects, Dave enjoys spending time with his young granddaughter, who keeps him grounded to the simple joys in life. Such joys for this wordsmith include reading prize winning fiction and non-fiction. Although a Connecticut Yankee, living for a decade in coastal California’s not too hot, not too cold climate epitomizes Dave’s favorite temperature, 75°F.

Temperature@lert Dave Ruede

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