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Temperature Sensor Tutorial & Buying Guide
A temperature sensor is one of the most simple, yet the most critical, pieces of equipment available to monitor your server room, server closet, data center, or other telecom environment.
Frequently, temperature monitoring using temperature sensors is ignored or overlooked by network operators. Unfortunately, it is incredibly important (and also quite inexpensive) to monitor temperature in telecom and IT environments. Both extreme cold and high temperatures present a danger to your valuable telecom investment, and you must take care to monitor for both of these potential threats.
Temperature sensors are simple and inexpensive
Temperature sensors are note at all complex, quite compact, relatively cheap, and they typically deliver an analog temperature value within one degree Fahrenheit of the actual temperature. Even those temperature sensors that operate like a thermostat (informing you only whether the site temperature is above or below the value that you have set previously), are far better than no temperature monitoring all.
Servers and other electronic equipment, by their very nature, generate large amounts of heat. If this heat is not monitored and controlled with one or more temperature sensors, skyrocketing heat levels will cause thermal shutdowns, service downtime, and even potential data loss and equipment damage.
In this diagram, an HVAC (air conditioning) failure occurred without knowledge of the network operators. No temperature sensor was in place to detect and report the high temperature, so equipment damage and data loss will result in expenses that could have purchased literally thousands of temperature sensors...
If your HVAC system stopped functioning and you had no temperature sensors in place that your remote site, you would have no idea of the rising temperature until it was much too late to prevent equipment damage and emergency shutdowns, which upset both your customers and your superiors.
Temperature sensors cut your costs and protect your revenue...
It's vitally important to monitor the temperature levels at your remote sites with temperature sensors. To get the most detailed visibility of site temperature, you need a remote that monitors four separate analog thresholds. With four thresholds you can set separate major and minor alarms for both high and low temperatures. This gives you both an advanced warning if temperatures are starting to leave the optimum range (e.g., the air conditioner is not working right and the temperature has risen to 85°F) and a final notification when temperatures have reached the danger point (e.g., the air conditioner is not working at all, and the temperature is 100°F).
Knowing both inside and outside temperatures gives you the overall picture. Imagine if the outside temperature is 120°F and your AC stopped working. With this knowledge, you'd know that you'd better dispatch a technician fast, as the temperature is sure to rise quickly.
The two types of temperature sensors
Temperature sensors come in two basic varieties. The simplest is a discrete threshold alarm. As I've explained, this type of temperature sensor operates much like your home thermostat. Just like you do at home to stay comfortable, you would specify a lower bound and an upper bound of acceptable temperature in your server room, telecom site, etc. any temperature above or below this ideal range would trigger an alarm notice so that you could take corrective action.
Unfortunately, the simplicity of this first type of temperature sensor can also cause trouble. If your alarm threshold was set to 85°F, analog might indicate that the temperature was 86°F or 186°F. You would have no idea of the intensity of the high temperature. Imagine that you have many sites with high temperature during a power failure or heat wave. This level of detail would not allow you to prioritize your technician dispatches to the hottest sites first.
An analog temperature sensor allows you to monitor the actual temperature at your site in near real-time. Instead of knowing that your temperature was merely "too high" or "too low", you would do for the temperature was, for example, 96°F.
You can use your analog values to send alarms based off of user configurable thresholds, allowing you to have different thresholds for low critical, low, high, and high critical temperature alarms. You would also be able to inspect the live temperature values in detail at the remote site.
But just because you have access to very detailed temperature sensor data any time doesn't mean that you can set automatic alerts when the temperature crosses a certain level. If you select high-quality alarm remotes to deploy at your remote sites, you'll be able to specify several temperature thresholds (the best alarm remotes support up to four thresholds) that will trigger an alert message to you when they are crossed. In this way, and intelligent alarm remote will provide the continuous and near instantaneous advantages of an analog temperature sensor with the automatic alert threshold advantages of a discrete temperature sensor.
How will you power your temperature sensors?
Most analog temperature sensors need +12V power. In a telecom environment, equipment is typically powered with -48V. You could run your temperature sensor off of commercial power, but during power outages you will lose your temperature sensor. An industry best practice is to use an alarm remote ("RTU" or "Remote Terminal Unit") that will provide power to your temperature sensor from a -48V power source (there aren't many, but the NetGuardian 832A has a built-in +12V power supply option for powering your temperature sensors). This ensures your temperature monitoring is online when you need it.
Another advantage of analog value alarm monitoring is the ability to monitor the escalation rate of the analog values. This would provide you insight as to how fast the temperature is rising or dropping, allowing you to better dispatch personnel.
Monitoring several locations within your remote site for temperature is a good idea. It is recommended that you monitor the temperature around your critical equipment, as well as the outside temperature. Excessive heat cooks electronic equipment, even carrier-grade telecom gear.
It's best to constantly monitor temperature at your remote sites with four-threshold and live value analog alarms.
Heat also damages other equipment. High temperatures will dramatically shorten the useful life of your batteries. A lead-acid battery that would last 10 years under ordinary conditions will last only a year if it's consistently operated at temperatures over 122 degrees Fahrenheit.
In a recent telecom case study, a telecommunications company lost a remote site with hundreds of thousands of dollars of equipment due to the lack of temperature monitoring. With the added heat radiation of servers and equipment, the site quickly turned into an oven - cooking the equipment beyond repair.
Beyond temperature monitoring - establishing a more reliable HVAC system...
It's important to monitor the HVAC systems that maintain your remote site environment. If you can catch an air conditioning failure early, you can intervene, start repairs and restore the remote site environment before equipment goes into thermal shutdown or the site goes dark.
Don't forget to also provide a secondary power supply for HVAC systems. An often-overlooked danger of power outages is that the telecom equipment will continue to run on backup power while the air conditioning, connected only to commercial power, is out. Imagine having the perfect array of temperature sensors in place, then not being able to respond quickly enough because you have no technicians in the area of the site with failed HVAC. The equipment keeps running, the heat keeps rising, until the temperature forces a thermal shutdown.
Real-World Examples of UPS Monitoring
If you do not deploy temperature sensors at your remote sites, you will, sooner or later, suffer equipment damage. One excellent example of the type of damage that can result comes from the world of UPS batteries.
Ambient temperature at around your backup battery cells must remain near the ideal level of 77°F. a higher temperature degrades the cells, and a lower temperature decreases the capacity of the overall battery string.
Server rooms and data centers also need temperature sensors. At DPS, we've spoken with several clients who have suffered multiple server shutdowns due to air-conditioning failures. We typically receive phone call that describe the following all-to-common situation:
"I need information about a sensor to monitor the temperature in my server room. We have a dedicated server closet but we've been having issues with the air-conditioning. Sometimes the AC will stop working for no apparent reason. It just happened again today, and I want some type of device that will monitor this in the future if the temperature starts to rise. I need to receive an e-mail that will alert me that the temperature is getting too hot."
In each of these cases, they successfully deployed small temperature sensors (and a controlling RTU device) that operate on the AC power typically available in IT environments. The sensors continuously monitor the server room temperature and send an e-mail notification when there's an issue.
In some climates, temperature sensors are even used to make sure that the temperature does not drop too low for equipment. We know that some users in Alaska are using hot plates to keep the oil in their generators from freezing up. Monitoring temperatures with high-quality sensors is critical to make sure that the hot plates are doing the job.
Subway operators have also been known to shut down their cameras and video servers when the temperature rises too high to prevent damage to this expensive equipment.
Some companies use temperature sensors to support "going green" initiatives by selectively turning off some of their HVAC units when they are not needed to maintain the ideal temperature range.
Even outside of telecom and IT, temperature sensors have their role. DPS Telecom has spoken with fruit packers who must monitor the temperature conditions around their fruit harvest, egg hatcheries that must monitor the temperature in their egg racks, pig farms have to make sure that there buildings do not drop below the level that the pigs require, and even a car wash in the northern region that needed to protect pipes against damage from expanding ice.
(Refer to this alarm features definitions page for definitions of unknown terms in this article)
Related Topics:
Temperature Alert
- Vaisala - Temperature/Humidity Sensor
- NetGuardian 832A (Large RTU to support multiple temperature sensors and other equipment alarms)
- TempDefender IT (Compact alarm remote designed for server rooms and data centers)
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