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Wireless Temperature Monitoring System Topology Considerations

Apr 21, 2014
Smart decisions during the evaluation process can help simplify the sensor network layout.

In this ongoing series centered around NYC Hospital Queens’ experience in selecting and installing a Wireless Temperature Monitoring (WTM) system to track medications and blood in hospital refrigerators (Link to Article) several factors as to the placement of WTM devices to support 174 refrigerators, freezers, and other critical areas in a hospital that is comprised of four main buildings, some built in the 1950s needed to be taken into account.

As was noted in a previous piece, the WTM system chosen at NYC Hospital Queens uses  wireless receivers located above the ceiling as communication bridges between the sensor modules and the hospital’s IT network.  The author notes, “signal strength dictates the number of receivers needed. Our institution comprises four main buildings, some of which were built in the late 1950s. Thus, the signal strength of the sensors in the oldest building was less than optimal and required the addition of multiple receivers to provide consistent readings. Basement areas also may require multiple receivers”.

Temperature@lert WIFI Monitoring Device

WiFi WTM device installed in server room provides a strong signal, good range and fast data rate without the expense of additional equipment (e.g. repeater/gateway).

Evaluating a WTM device’s signal strength or range in all of the locations to be monitored is paramount before selecting any one technology. Depending on the wireless technology chosen, each wireless sensor type may require more or fewer receivers to make the connection, resulting in more or less complex and higher or lower cost deployments.  NYC Hospital Queens could possibly have chosen a device that does not need a receiver (a.k.a. gateway) but had sufficient signal strength to communicate to the site’s IT network directly.  A standard WiFi device could potentially provide such capability without the added expense of a receiver/gateway device.

Mesh network showing sensor nodes (red/green) and receivers/gateways (red).  In this case some sensors also act as gateways and can help link remote sensors without the added cost of a dedicated gateway. (Link to Source)

Some wireless technologies are able to overcome interference from the building infrastructure, equipment or furnishings that others may not. Other wireless technologies have mesh network capability, meaning the wireless sensors or receiver/gateways can communicate with each other. Therefore when one device is not operating properly or experiences signal degradation caused by interference, the device can communicate with an alternative neighboring device to maintain the network integrity. And still other WTM designs employ receiver/gateways that can contain their own temperature sensor(s) in addition to serving as a gateway, providing an additional pathway to lower the complexity and cost of the system. Evaluating wireless devices from several vendors, each using different wireless technologies, WiFi, ZigBee, RFID, Bluetooth, proprietary, etc. can help the user understand how each works in the various locations to be monitored.

But what does one do when these technologies don’t work or are not feasible for a hospital’s IT network? For example, some IT departments are averse to adding new devices to their internal networks due to security or capacity capacity concerns because continuous temperature monitoring of 174 sensors in the case of New York Hospital Queens for example can generate a lot of data quickly. To meet the hospital’s need, historical data needs to be maintained, secured and stored for an extended period of time for regulatory purposes. Adding alerting capability to the WTM system, for example sending e-mail, text or phone call messages when something goes wrong, means an additional level of IT capacity is needed to send and log these alerts. Adding an escalation plan for times when issues do not get resolved in a timely manner adds an additional level of complexity. Close collaboration with the hospital’s IT resources will be needed to determine what is possible and what is not.

Temperature@lert How It Works

If IT capacity or network policies make it very difficult if not impossible to add a WTM system, what options exist? One good option is a cellular gateway that communicates directly to the wireless sensor network and uploads data to cloud based sensors via major carrier cellular networks. Temperature@lert’s Cellular Edition is one such device. Each Cellular Edition is equipped with a cellular transmitter/receiver that communicates through national cellular carrier networks to Temperature@lert’s Sensor Cloud web based storage, reporting and alerting services. Each Cellular Edition can link to several Z-Point wireless sensor nodes resulting in up to 45 sensors being monitored via one Cellular Edition gateway depending on signal strength and equipment layout.

Understanding how any new wireless network will operate at a site requires study and testing. Once the locations to be monitored are mapped and solutions that the organization’s IT department supports are determined, those tasked with the WTM decision are ready to make their recommendation. This all takes time and energy, so add that to the planning process and everyone will have a better understanding of who, what, when, where and why the final selection is made. Because once this happens and the installation starts, it will be good to have the history to remind all how they got here.

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.

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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