How To Sense Temperature with a CLICK PLC from AutomationDirect

reading temperature with a click PLC is easy in fact this is all the code you need right here don't see any me neither there isn't any you don't have to write a single line of code to get the temperature with a click PLC now you'll have to write code to use the temperature of course but once everything's set up the input temperature values just appear in this example we have a click PLC connected to two thermocouples 2 RT DS and three different types of temperature transmitters a sensor head mounted transmitter and integral transmitter and a fixed din rail-mounted transmitter here's what it looks like on the test rack here's the click PLC here's the two thermocouples here's the two RT DS and here's the three different types of temperature transmitters they're wired exactly like the block diagram shows the cable shield is grounded only at the sensor end not at the plc end in general you'll always want to ground the shield at the signal source end and definitely at one end only otherwise you'll end up with another current path which could create a ground loop and actually make things worse than having no shield at all and the thermocouples use the special thermocouple din rail terminal blocks these ensure continuity the special thermocouple wire by clamping the wires together instead of contacting them through a terminal block which would create unwanted thermocouple junctions well that's it for the hardware let's look at the software as we mentioned earlier you don't have to write any code to get the temperature values you just configure the click to do it for you the cool thing about the click PLC is when you connect to the click the software automatically identifies all the modules you have plugged in we can see that under system configuration the software reminds us to select the power supply we're using and that the modules has not been set up yet we know that so we had okay we're using the AC supply so we select that now we can see how we're doing power budget wise let's see we're only using 340 milliamps of the 1,300 available so we're in good shape the software found an 8 input digital module an 8 output digital module a 4 input analog 4 to 20 mili-amp card a thermocouple module and an RTD module perfect to set up the analog module we just hit configure our temperature transmitters are connected to these first three channels and in providing a 4 to 20 milliamp loop so we'll need to put force here the first transmitter is a programmable sensor head transmitter that's been configured to give us 0 to 100 degrees F and we'll put that in memory location DF 30 this checkbox up here says just fill in the rest of the registers for us I really like that the second temperature transmitter is an integral temperature transmitter and it's fixed at 0 to 100 degrees C which is 32 to 212 degrees F and the third transmitter is at NREL thermocouple type J module with a fixed output of 0 to 100 degrees F and that takes care of our temperature transmitters let's configure the thermocouple module we're only using two of the channels and we want the result to be in degrees F they both happen to be type J thermocouples using this temperature range and we'll put them at memory location D F for T and click this guy again to fill in the rest this module supports a wide array of thermocouples and one key feature is you can specify a different type of thermocouple for each channel some PLC's mandate that you have to use the same thermocouple type on all channels of the module and when choosing a standard probe type the scaling is set up for you you don't have to fool with that the only time you need to set up scaling is if you're using a custom voltage range now this thermocouple module provides indications at these input values to determine if the sensor is open or under or over voltage and you can detect when two modules initializing or not functioning those are awesome features to take advantage of in your ladder code ok finally let's configure the RTD module here's a little trick instead of clicking configure you can also just double click on the module we're using two of the RTD channels and we want the results to be in degrees F both RTD SRPT 100's over this temperature range this module supports all these kinds of RT DS and just like the thermocouple module you can specify a different RTD type for each Channel we'll use this option again and let's start the RT DS at memory location DF 50 again on this module you can read these input values to determine if the sensor is open or under over-voltage and you can detect whether the modules initializing or not functioning don't ignore those they can be real handy when you're trying to debug things well that's it we just configured seven temperature measuring subsystems in about two minutes let's transfer the program to the click PLC and see what happens here's a data view showing us all of those temperature values the values would normally be pretty close in temperature but I've been messing with them so they're still settling down here's another key feature that click PLC the values shown are the actual temperature values some PLC's give you a number with an implied decimal point so instead of 77.2 degrees you get seven seven two degrees and you have to remember that there's an implied decimal the click gives you the actual decimal temperature value if I put a cup of cold water on one of the probes and hot one another then the values change accordingly I set up a c-more HMI to monitor the values - if we swap the probes then we see the results graphically perfect if I disconnect one of the wires the indicator that's monitoring that contact provided by the temperature module lights up so I instantly know there's an issue with the wiring of the sensor I love that feature and again we haven't written one line of ladder code to get these temperature values if you have any questions or need any help please don't hesitate to contact 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