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LE 10 - Measuring temperature with a PID controller

 WARNING

Make sure the whole control station is not energized before touching or starting your exercise!

This experiment deals with measurement with a thermocouple probe and a PID controller. For this, the most simple functions of the controller are to be used. However, even for this, you need to take a look to the instruction manual and check for the right path in the menu.

Objective

Temperature measurement with a thermocouple and a PID controller while exploring the configuration menu of it.

Material

Fig. 01 Electric terminals for EMKO-9930 PID controller


What to do

For this activity, you will need to use the same ladder diagram installed for turning on the PID controller. Rememeber that, your installation should have the following features,
  • The PID controller should turn-on with the green button. Also the green pilot light should turn-off and the red pilod light turn-on as this button is pushed.
  • The PID controller should turn-off with the red button. Also the green pilot light should turn-on and the red pilod light turn-off as this button is pushed.
  • There should be an emergency stop button so that as it is activated a yellow pilot light turns-on, indicating an alarm.

Read the PID controller electrical diagram to learn in which terminals connect the thermocouple sensor. Recall that in the test stations there are two PID controller models: ESM-9930 and XMT-A808. You may download the instruction manuals in the following links:

Fig. 02 These are the two models of PID controllers available


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Fig. 03 Electric terminals for XMTA-808 PID controller


How to do it

Step 1. Identify terminals for thermocouple

Look carefully at the PID controller your station has. Then take a look to the electric diagram. The electric diagram can be found either in the instruction manual or printed in the controller case.

You should verify that for EMKO-9930 these terminals are (1,2) while for the model XMT-A880 these are (1,2) as well. Be aware of not wiring the voltage supply to these terminals or you could blow up the controller.

Step 2. Turn-on the PID controller

This is easily done by just pushing the start button. You will have to give a few seconds to the controller so that it can fully initialize.

Step 3. Set-up the corresponding thermocouple and units

The PID controller does not know the type of thermocouple you are connecting. Therfore, this must be set-up before any measurement.

For this step, you will need to read the corresponding instruction manual and follow the steps to navigate through the controller menu. Below, Figs. 4-5 give this help for one of the controllers.

Fig. 04 Menu for thermocouple set-up for the EMKO-9930 controller. Follow the coloured lines.


Fig. 05 Options for setting-up different types of thermocouples for the EMKO-9930 controller. Notice that for each thermocouple two options are available. The first option gives temperature readings without decimals while the second option provides one digit after the point for more precision.


Carefully review the other instruction manual to find the corresponding path to navigate the menu and set-up the controller properly.

The temperature reading should be given in the screen of the controller. You may supply a heat source to the joint point as to see if the temperature changes. Use ice or a lighter if you wish.

Try programming the controller to give the temperature measurement in Fahrenheit rather than Celsius degrees and vice versa.

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