How to Design a Temperature Monitoring System

Temperature monitoring systems are incredibly useful tools to monitor and manage your heat levels at all of your remote telecom sites. While "too much heat" is the most common problem when dealing with computer systems, "too cold" is also a very real problem in some climates, as you'll learn.

A temperature monitoring system will help you to avoid heat buildup at your telecom locations, like huts and other network nodes. Temperature monitoring is also important at less industrial "IT" locations like server rooms and data centers. The right temperature monitoring system will enable you to keep track of critical temperatures at all of your sites that contain important computer gear.

1. Choose a Sensor

The first consideration you have in evaluating temperature monitoring systems is what type of sensor to use.

Analog sensors are superior to digital sensors, because they measure temperature across a continuous range. Digital temperature monitoring, by contrast, will only tell you if the temperature is above or below a pre-determined value. There's no way to know how much the temperature has risen (or fallen) beyond the temperature you specify.

Analog sensors are recommended in most cases when you're setting up a temperature monitoring system. That's because, even as they offer the ability to check the precise temperature at any time, they can send you alerts when a specific threshold is crossed (the only real value of a digital sensor). If cost is a big factor in your decision, however, a digital temperature sensor is 100% more useful than nothing at all.

Here, the NetGuardian 216's web interface provides a highly visual system for monitoring temperature remotely.

2. Choose an RTU

To get the threshold alert capability with analog sensors, as I've just described, you need to select the right alarm remote (RTU) to link your sensors from your remote site to your central office.

An RTU bridges the gap between your sensors, which communicate with simple voltage/current (analog) or discrete contact closures (digital), and you central office.

Actually, an RTU can send temperature monitoring system alerts to other locations if your company doesn't have a 7x24 network operations center (NOC).

Whenever you NOC is not staffed (which could be "all the time" if you don't have one), good RTU's will send you email temperature alerts or send text/voice messages to your phone. If your NOC center is open, your RTU can send a protocol-based alert (usually an open protocol like SNMP is best) directly to your central master station (commonly an SNMP manager). Your monitoring team/dispatchers will then be able to assess the urgency of the temperature threat and deploy the right personnel or take the appropriate remote action (like activating backup HVAC or opening vents).

3. Don't Forget to Plan How You Will Power your Sensors

One often overlooked (until the install goes sour) factor when designing a temperature monitoring system is considering how you will power your sensors.

You have a couple of solid options here, but it's amazing how many network professionals end up doing something sub-par.

First, you can use sensors that are powered directly from the RTU. This takes one of two forms. Some RTU's have a small stereo jack port that supports an external sensor. This sensor is incredibly small. In fact, to the untrained eye, your RTU will simply have a 7-10 foot wire plugged into it. On the far end of that wire, however, is actually a tiny analog temperature sensor that is entirely powered by the RTU.

You can also use direct single wire (one popular name for this is "D-Wire") temperature sensors that use one wire to transmit both communication and deliver sensor power. What's more, these sensors are daisy-chainable. A single RTU input port can accept multiple sensors in this way, allowing you to effectively monitor temperature at several key locations within your site with a minimum of fuss.

Another option when using industry-standard external temperature sensors (those that output either between zero and five volts or between 4 and 20 milliamps) is to select an RTU that has a built-in twelve volt (+12 vdc) power supply. This is the voltage that most external sensors require. Choosing this type of RTU is convenient, because you eliminate the need to separately wire and power your sensor.

Running a giant external power transformer brick is a silly proposition when powering a little sensor. Most of the time, your power brick will be much larger than the sensor it powers. Don't fall into the trap of thinking this is the only way. You can do much better when building your temperature monitoring system.

4. Make Sure to Get the Right Capacity for You

As you can see remote temperature monitoring systems can vary in quality quite wildly depending on the choices you, the system designer, make while researching and purchasing equipment.

The sensor-power capabilities of your RTU are important, but there are many other considerations you need to make to select the perfect RTU for monitoring temperature at your sites.

You need to choose a remote that has the sensor capacity you need. If you just need to monitor one or two sensors, there's little sense in purchasing a remote with dozens of sensor inputs. Of course, the opposite is even worse. Purchasing an RTU with too few sensor inputs means that you won't have adequate monitoring. Every hole in your temperature monitoring system is another potential network threat that you're not protected against.

Featured Temperature Monitoring Systems

We really should spend some time looking at a specific temperature monitoring system offering from a contemporary manufacturer.

Let's begin by reviewing an RTU that's built to handle server rooms, data closets, and even telecom environments. This RTU is the TempDefender IT. It's a small RTU that include the "D-Wire" sensor interface described above. While it supports up to 16 sensors total, it's also a good value with just a few sensors because of its daisy chain capability. If you only need a few sensors, you only need to purchase a few sensors. The RTU remains a good value with just a small number of sensors.

If you'd like your temperature monitoring system to call you when alarms occur, there's another small remote you should consider: the NetGuardian LT. This RTU will call your phone (either cellular or landline) whenever a temperature situation demands your attention. Especially if you have just a few areas to monitor, this is a one-box approach to a temperature monitoring system. As you'd expect, it's also one of the most cost-effective.

The TempDefender and the NetGuardian 832A are two good options of RTUs to monitor the temperature at your remote sites. Your choice will depend on your capacity requirements.

But if you work for a medium-to-large company and you have lots of equipment and sites that require temperature monitoring, you'll be much better served selecting a larger RTU like the NetGuardian 832A. With 32 digital inputs and 8 analog inputs, it has the capability to monitor as many sensors as are required at all but the largest installations.

Real World Scenarios

To help you better understand how temperature monitoring systems work, let's take a look at a project from DPS Telecom's recent history.

One day recently, Evan called in looking for a small RTU. He had 1-4 sites that needed to be covered by a temperature monitoring system, among other types of monitoring. Evan needed about 8 discrete alarms points, 3 control relays, and 1 serial port for COM port redirect. He also wanted 1-4 generic analog inputs (for collecting sensor data from temperature sensors and other sensors).

A big issue for Evan was windshield time, the hours that technicians spend traveling to and from remote sites. For Evan's company, some sites were up to two hours away from the central office. This puts wear and tear on vehicles and costs a lot of money for gas, not to mention the highly paid technicians who are logging hours for driving around.

Evan had a couple of sites that were solar powered with generators that run when the panels do not create enough electricity. The generators had problems when they had to kick on and off a couple times a day.

 This remote temperature sensor has a visible meter if you happen to be at the site, but it also transmits temperature data back to you.

 If the generator did not start, they would have the inverter cut out so the batteries were not drained to point of damage. This would cause the site to go down.

We received this email from Evan, describing more of his need for a remote monitoring system that included a temperature monitoring system:

"This is a remote communications site with a microwave link and Ethernet connectivity to our own intranet. Likely power the unit off 110 VAC, though we might prefer to put in a DC-DC converter off the +48 VDC bank unless your unit will run off as high as +60 VDC. Site is solar powered with 4 Outback charge controllers, 4,000 Ah of batteries, 15 KVA of Outback inverters and a 30 KVA generator.

We would want to monitor:

  • Battery bank voltage 48 VDC nominal
  • Inverter AC output voltage 120/240 VAC 1-phase
  • General Fault from generator
  • Inside temperature
  • Outside temperature
  • Generator running indication (switch closure or AC voltage measurement)

Control via relays:

  • Fault Reset to generator
  • Diesel tank heater load shed (activate contactor coil)
  • Generator external run command

Nice to have:

  • Inexpensive webcam interface, that is a USB camera, etc.
  • RS-232 port to connect to Outback MATE serial port
  • One to four DC current shunts, 100 Amps, to monitor solar charge controller output(s)

Sincerely, Evan"

Talk to Our Experts

I hope this introduction to temperature monitoring systems has been useful for you.

If you want to know more about remote monitoring and start planning your temperature monitoring system, give us a call and one of our experts can help you make informed decisions.

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