How to Choose a Remote Temperature Sensor for Telecom Site Monitoring

By Andrew Erickson

September 4, 2022


So, you've decided that it's time to remotely monitor your telecom site's temperature. Where do you even begin? Let me walk you some of the basics associated with this important buying decision. Once you understand the fundamentals, I promise that you'll be able to make a great decision that will serve your company well.

Respect the seriousness of this simple sensor

Before we even begin, you really need to think about just how important your operation is to the general public. What would happen if people couldn't use your services? Would they be able to dial 911? Would the power grid stay on? Would transportation continue to move?

If you deal with telecom sites, whether you work at a telco, power utility, railroad, government agency, or anything else, the people you serve deserve high reliability.

When we're talking about something as simple as buying a remote temperature sensor, there's really no reason to pinch pennies. You might find a temperature sensor that costs $30. You might find a temperature sensor that costs $500.

All of these costs are quite trivial if they can actually guarantee even a sliver of additional uptime for your network. Still, there's no excuse for outright wasting of your budget dollars.

So how do you tell the difference between what aspects of a temperature sensor are actually important and which parts you can do without? The first step there is obviously to understand what differences exist among temperature sensors and what the value of each is.

Discrete/Digital vs. Analog temperature sensors

Some temperature sensors are digital, while most in the modern age are analog. This is not to be confused with analog and digital communication, where digital is the more modern solution.

When I say "analog" in this context, I mean that the temperature sensor itself is able to output a range of possible values. You see this every day when you look at a temperature display on your oven or perhaps on your car dashboard. You don't just know whether or not the temperature is above or below a certain threshold. You actually know precisely what the temperature is.

Compare this to a "digital" temperature sensor. The best example you've probably dealt with in daily life is your home thermostat. While it has an analog component in that it tells you what the current temperature is, its output is solely digital. The air conditioner has either been told to activate or hasn't.

Powering your temperature sensor

It's also important for you to consider what sort of power source your temperature sensor will have. A temperature sensor that runs on 110 AC is a lot better than nothing, but that power might actually go down in the event of a commercial power failure.

Temperature sensors that run on the more commonly protected -48 VDC or +24 VDC are going to be more reliable in the long run. Even if you have a commercial power failure, sensors running on these DC voltages will be unaffected.

Of course, the ultimate solution in remote site temperature sensing is to use something that is bus-powered. Sensors of this type are powered by the very same cable that carries their data. It's one less thing that you need to worry about when you're wiring up a site. If you can talk to your sensor, it has power.

Monitor the correct temperature range for your application

The measurable temperature range of a sensor is also important when you're doing your shopping and planning. For many use cases, anything in the range of "slightly below freezing" to "just below boiling" is going to be acceptable for most monitoring of air temperature. Of course, if you live in a very hot or very cold climate or you are monitoring liquids in an industrial context, you may need to choose a different type of temperature sensor.

You have to match data transport to your overall monitoring system

Data transport is also a consideration you need to make. The simple discrete temperature sensors that only measure whether you are above or below a certain value don't need much. In this case, a simple contact closure or binary Modbus register value may be all that is required.

Analog temperature sensors have more data to transmit and, therefore, involve somewhat more complex decisions. You could embed analog temperature data in an SNMP trap. You could scale it as a value between 0V and 5V.

Fortunately, you don't have to be an electrical engineer or computer scientist to make these things work. It's just important that you make purchasing choices that will ultimately be compatible with each other.

For example, if you have an SNMP manager that you're using for your remote site monitoring, it will be perfectly fine to choose a network-capable temperature sensor that can send SNMP traps back to that SNMP manager.

If you have a rugged RTU at the site already that has analog input circuits, then a scaled voltage value is probably the right choice.

Choose a partner you can work with for a long time

Lastly, you should also never discount the value of choosing a reliable vendor or manufacturer. The construction of an effective remote site monitoring system that includes high-quality temperature monitoring is not something you ever truly finish. You need a partner to help you over the long haul to evolve your system to meet evolving challenges.

As you're doing your shopping, ask every vendor or manufacturer that you speak with how long they've been doing this. Are they specialists in remote monitoring, or is it just one of the many many things that they do?

If you find yourself interacting with little more than an e-commerce website and clueless representatives behind the phone line, that's probably not something that you want to be stuck with for years to come.

Give me a call to discuss your monitoring options

Whether you only have questions about temperature sensing or you're working on an entire monitoring system, I'm here to help you.

Give me a call to ask whatever questions you have. I'll match your problems to the right solutions, even if they don't involve DPS.

Call me at 1-800-693-0351 or email me at sales@dpstele.com

Andrew Erickson

Andrew Erickson

Andrew Erickson is an Application Engineer at DPS Telecom, a manufacturer of semi-custom remote alarm monitoring systems based in Fresno, California. Andrew brings more than 15 years of experience building site monitoring solutions, developing intuitive user interfaces and documentation, and opt...

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