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Electrical Power Options For Wireless Temperature Monitoring Devices

Apr 07, 2014

Understanding WTM device configuration options is a beginning.


Unless one uses a thermometer to monitor temperature, electrical power is needed to power today’s temperature monitoring devices. And there are several choices for electrical power options as will be described below. One factor in determining what electrical power source is best for any particular site is the Wireless Temperature Monitoring system configuration, and there are several to consider each with its own costs and benefits.

This seventh piece in our series series is prompted by an article on the Pharmacy Purchasing & Products website describing the use of Wireless Temperature Monitoring (WTM) systems to monitor medication temperatures in hospital refrigerators. (Link to PPP Article) The Pharmacy Purchasing and Products posting titled NYC Hospital Examines WTM (Wireless Temperature Monitoring) options notes there are several factors to consider in understanding which device will work best to help protect the safety and efficacy of temperature sensitive medicines and products such as vaccines and blood.

Although the supplier of the WTM system selected by NYC Hospital Queens was not identified, the author did provide some insight into the system design and configuration. “Initially, we opted to use wireless sensors with powered (120 volts) receivers. However, it quickly became clear that maintaining access to a power supply would be a challenge because most receivers are located above the ceiling where access to a 120 volt power supply is limited and requires the additional services and expense of an electrician. Our engineering department estimated that there would be a significant cost associated with transferring data from the sensor to the receiver. Thus, the powered receivers were swapped for receivers that worked with our Ethernet network, which resulted in significant cost savings.”

In NYC Hospital Queens the issue of power became a significant consideration to help determine the types of devices installed. But what are the choices. Taking a step back, temperature monitoring systems can be designed in several ways. Here are some common wired and wireless examples.

     1. USB device (Wired) - plugs directly into computer or server USB port, powered by USB port

     2. LAN (Ethernet, Category 5, Cat 5, Cat 5e) device (Wired) - requires Ethernet cable to connect to the site’s IT network, powered by AC or PoE (Power over Ethernet)

     3. WiFi Standalone device - wirelessly connected to the site’s existing WiFi network, AC or Battery powered

     4. LAN Gateway** device (AC or PoE) with wired or wireless* satellite sensors (AC or Battery)

     5. WiFi Gateway** device (AC or Battery) with wired or wireless* satellite sensors (AC or Battery)

     6. Proprietary Wireless Gateway** device (AC or Battery) with wired or wireless* satellite sensors (AC or Battery)

     7. GSM, CDMA, or LTE Cellular Standalone device (AC or Battery) with wired sensors

     8. GSM, CDMA, or LTE Cellular Gateway** device (AC or Battery) with wired or wireless satellite sensors (AC or Battery)

*Wireless satellite sensors can employ WiFi, ZigBee, Bluetooth, RFID, Proprietary or other wireless communication technologies. The two previous pieces in this series discuss these options as they relate to monitoring hospital medical refrigerators.

**Gateway describes the wireless sensor interface to the site IT network.

Graphic showing possible components of WTM devices.

Graphic showing possible components of WTM devices.

Selection of the type of sensor, interface and data collection device will have a significant impact on the type of electrical power required to operate the system without continuous maintenance. Other configurations may exist but these configurations are representative of those found in today’s market.

For example, below are four Temperature@lert temperature monitoring devices for consideration. From left to right, the Z-Point wireless sensor operates on AA Li-Ion batteries for up to five (5) years with five (5) minute monitoring intervals; the Cellular Edition normally operates on AC power (110/220 VAC) and has backup battery power for times when electrical power is interrupted’ The USB device is powered through the USB port of a computer or server, and the WiFi device requires 110/120 VAC electrical power or Power-Over-Ethernet through the device's LAN connector to operate.

Temperature@lert Z-Point Wireless sensor, Cellular Edition Gateway, USB Edition, and WiFi Edition temperature monitoring devices.


Left-to-Right: Temperature@lert Z-Point Wireless sensor, Cellular Edition Gateway, USB Edition and WiFi Edition temperature monitoring devices.


Facility operations, conditions and requirements will help determine whether or if AC or battery power meets the site’s specifications and needs. In the case of NYC Hospital Queens, AC power was not available for the sensor gateways but Ethernet (LAN) connections were available. Ethernet (LAN) connectors can be configured to deliver power to devices connected to them; the technology is called Power Over Ethernet (PoE), and this was a more cost-effective choice for the hospital's installation. What is the impact of the choice on operation of the WTM system. The next piece in this series will examine the pluses and minuses of different electrical power options and provide some insight into best practices.

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 http://www.temperaturealert.com/ 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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