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Pid Wiring / Calibration Help Please!

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jonw

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I have a PID controller with a pin-out per the photo below. I have a cheap PT100 probe with 2 blue connectors and 1 red one. I've connected the red connector to pin 5, and the 2 blue ones to pins 3 and 4 (any other configuration just gives an error.)

This seems to work OK, except for the temperature reported is about 5-6 degrees below what my other thermometers read. Have I got the wiring wrong? If not, is there a way to calibrate these things?

Edit: Could it be the cheap PT100 at fault?

Cheers,

Jon


photo.JPG
 

billygoat

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That controller looks like it can also take a K type thermocouple input, make sure you've got the controller configured to accept a PT100 input if that's what you are using.
It also looks like the blue wires should be connected to pins 4 and 5 and the red wire to pin 3. If you have a multi meter, the blue wires should show a short circuit when you measure between them, and if you measure between the blue wires and the red wire you should have around 110 ohms depending on the ambient temperature. At 0 degrees the PT100 should show 100 ohms when measured between the blue wires and the red wire.
 

brettprevans

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Pm fourstar. He recently had to calibrate his pid as it was a bit screwy.
 

matho

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they way PT100 sensors work is there are 3 leads, 2 of them are connected together at the end of the sensor and are used by the sensing unit to remove the resistance of the leads, these 2 leads are connected to one end of a resistive junction the other of the junction is connected to the third wire, if you have a multimeter connect between 2 wires at a time between 2 wires you should almost get 0 ohms and between one of those wires and the other one you should get resistance very close to these PT100 vs temp that should tell you that the pt100 is working. From the drawing you would have to connect the 2 shorted wires to 4 and 5 and the one that returns the resistance to 3. I also noticed that the unit says its for a k type thermocouple, some units allow you to change this, do you have a manual for the unit?

cheers steve
 

Crazy

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That controller looks like it can also take a K type thermocouple input, make sure you've got the controller configured to accept a PT100 input if that's what you are using.
It also looks like the blue wires should be connected to pins 4 and 5 and the red wire to pin 3. If you have a multi meter, the blue wires should show a short circuit when you measure between them, and if you measure between the blue wires and the red wire you should have around 110 ohms depending on the ambient temperature. At 0 degrees the PT100 should show 100 ohms when measured between the blue wires and the red wire.
 

bulp

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Gday jonw

You need to change your thermocouple type in this menu


Screen_shot_2012_04_28_at_10.18.00_AM.png

Screen_shot_2012_04_28_at_10.18.14_AM.png

And definately calibrate the probe after this step, i've made that mistake before i had 2 C difference , if you need to calibrate it use this menu :

Screen_shot_2012_04_28_at_10.24.42_AM.png

Hope that helps they can be confusing .


cheers
 

jonw

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Thanks guys. Unfortunately I don't have a multimeter, so I can't check the connections to the probe. However, the PID reports an under scale (check your wiring!) error with it wired up any other way than the way I have it. I hadn't found the PV bias value, which sounds like it's what I need. I've adjusted that so that the unit reads the same as my digital thermo, and I'll run the my HLT through a few cycles and make sure it settles on the same temp.

Thanks again.

Cheers,

Jon
 

matho

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hope it works for you, if you do end up getting a multimeter I would recommend getting a CAT III class of multimeter which really is the minimum that you should use on mains powered devices, Jaycar sells a $30 CAT III multimeter which would come in handy when working on projects like these.

cheers steve
 

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