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Learn about all the different types of temperature probes and which ones will work best for your application..
AutomationDirect offers a lot of different styles of thermocouple and RTD sensors so figuring out which to use when can be a little daunting. In this video we'll take a quick look at each so you know how to choose the right sensor for your application. All of these probe types are available in either RTD or Thermocouple sensors, except the Sanitary Head and M12 probe type which are only available with RTD sensors. These guys have a threaded hex nut so you can insert them directly into a process container. You would typically put some Teflon tape or pipe sealant on the threads, screw the entire unit in, tighten it down, and then attach your conduit. Unscrew the cover to connect the wires and you are ready to go. If your application is too harsh for the probe by itself maybe it's too corrosive or maybe you have solids or particulates flowing by that would beat the probe to death then you'll probably want to use a thermowell which you screw into the process container then you screw the probe into the thermowell. In this case you'll want to use a spring loaded sensor head with a probe that is a little longer than the depth of the thermowell. So when you screw the probe in, the spring presses it firmly against the bottom of the thermowell to give you the best possible thermal transfer and the most accurate readings. You wouldn't want to use these spring loaded guys without a thermowell, because they aren't sealed and your liquids would leak back into the sensor head and even the conduit! The last option that these standard sensor heads have is the same stainless steel version as the first one, but no threads. You use a compression fitting with this one. With the compression fitting in the process container, you can now adjust how deep the probe enters the container, then tighten down the compression nut and you are good to go. This guy is especially useful when you have a pipe with a lot of insulation and you want to keep the head out where you can get to it. With the compression fitting you can just purchase a sensor head with an extra long probe, slide it into the compression fitting and keep the head out where you can get to it. In addition to the standard sensor head, there is also a sanitary sensor head with a plastic house and a tri clamp mount so it is quick and easy to disassemble for cleaning in applications like food and beverage operations. All of these service heads give you excellent protection of the electronics, while also providing easy access to the wiring for testing and maintenance. If you need to quickly plug and unplug probes for fast swap out, and minimal down time, you can't beat these convenient plugs. The RTD probe has the expected three wires and the Thermocouple probes are color coded for each type of probe. Each connector is polarity protected and the plus and minus terminals are labeled right on the connector. The plugs and jacks are available individually so you can make your own probes, connectorize probe wire connections, or make your own extension cables and there's a panel mount version which is also available. All of these are available in standard and miniature sizes. If I hold them side by side you can see the difference in size between the two. There's also a metal strain relief for each side that you can use to help protect the wires. Adjustable immersion probes make attaching a sensor to a pipe easy. Adjust the pressure by moving this bayonet cap up and down the spring then lock it in place. You now have a good reliable contact with that pipe. Standalone bayonet mounting adapters are also available in various lengths so you can attach them to whatever you want. Same thing, adjust the cap to the length you need, then lock it in place. The armor version of the immersion probe does the exact same job, you just screw the cap up and down the probe to adjust the pressure of the sensor. It just has this outer shell or armor for those tough or harsh environments. Sometimes you'll just want to bolt a sensor right to surface. These are available in brass and stainless steel. They both do the exact same job, but your application may dictate which you need to use. For example, you'll want to use the stainless steel one if you are in the food and beverage where frequent wash down is required or if you are in a corrosive environment. These are ideal for nozzles, extruder barrels, die heads, molds and pretty much anything where you need to bolt the sensor right to the surface you want to measure. Of course there is also just the probe all by itself with lead wires. You would typically use this with a compression fitting and a plug and jack like this. This is a type K thermocouple, so you would want to use the yellow plug and jack or if the plug is going to be exposed to over 400 degrees F, then use the brown plug and jack they are still type K but rated for higher temperatures, up to 662 deg F. And sometimes you just want to measure the temperature of a room but dont want a ugly sensor dangling around. This is just a ventilated housing with a sensor in it. It's available in both Thermocouple and RTD. This probe provides a convenient M12 cable connection BUT it is only available as an RTD which makes sense right? The M12 cable is only going to have copper wires so it can be used with a Thermocouple. So if an RTD will suit your needs, this is an excellent way to connectorize your temperature measuring system. There's no adding connectors and wiring, just plug the M12 cable in and your are ready to go. There are two different wiring diagrams for the M12 Probes. The 6mm diameter probe has a three wire connection. The 10 mm diameter probe has a four wire connection, which is required by some systems. If your controller has only a three wire connection, can you use just three of the 4 wires? Sure. The RTD isn't polarity sensitive, so you can use either pair as the loop back pair. It's good practice to connect the extra wire to its mate. One cool thing about this M12 probe is you can get a transmitter that just plugs right in. That way you can start off sending temperature data back to your PLC, but if later your controller has to be moved and you need to extend the distance to the probe or maybe you find you need better noise immunity, you can quickly drop a transmitter in place without having to swap everything out. We'll talk more about these transmitters in the video on remote temperature sensing. There are also some sensors with integral transmitters and temperature switches with adjustable set points. Those will also be covered in the video on remote temperature sensing. If you have any questions, please, don't hesitate to call AutomationDirect's free award winning tech support during regular business hours they will be happy to help you. And don't forget the forums there are lots of folks there that love to share their years of experience. Just don't ask any tech support questions there. Tech support doesn't monitor those forums on a regular basis.