Temperature control of Mitsubishi FX3U 4AD.

Hi guys

I am trying to change the setpoints on a PT100 that i have in a tank that is controlling a process. I am using GX works software and the temperature control module is an FX3U 4AD. The thing is i am a novice at this and i am not sure how to navigate through the software to find this or how to begin. The PT100 is using 3 setpoints to heat and cool a process 110 degrees c then 100 and then to 80 i just want to change the 110 to 100 but i am not sure how to go about this. I know this may sound silly but i was expecting to see the values somewhere in the program ie. 110c 100c 80c. but all i see are the M8000 etc and dont know how they relate to the setpoints

Do you use FX3U-4AD or FX3U-4AD-PT?

Fx3u-4ad-pt

From a glance at the installation sheet for that module, it appears that it is a signal conditioning module for a Pt100, an RTD temperature sensor.

The temperature signal from that module will be an input to either an on-off control (comparator) function or a PI/PID controller. The SP would be associated with the oontrol function, not the temperature signal.

A setpoint is also likely to be a remote function done in an HMI, and then communicated to the controller in the PLC.

Install library in attachment and use the function...

Best regards,
Goran.

thanks guys i am actually having another problem with this now as when i am in monitor mode it is only letting me view it as read only and i cannot make changes why is this so? and how do i unlock it from read only

And Goran i cannot open that file

It is library - you need to install it in GX IEC Developer or GX Works2.

If I remember correctly the AD PT is analog in only and not the PID controller card that is a 2LC card, however to read the analog inputs from the card you need to set the card up with a TO instruction on first scan of plc then on every scan read the channels from the card using the From instruction, the information usually comes with the card or you can download the manual from the Mitsubishi website.
http://dl.mitsubishielectric.com/dl/fa/document/manual/plc_fx/jy997d16701/jy997d16701p.pdf

I agree with DanW

You have a working program right now. The PT100 is programmed and working. You need to look at the device doing the heating. Probably a 4-20mA output to a control valve or something like that. Then find that devices address and look in the code for that address using search function

The set point is probably set either as a constant or as d DanW said, from a HMI or BMS etc so it may be a value in a D register

Great guys thanks for the info

Hi guys

Back again i have actually traced the problem back to the HMI controller on the heater unit itself. The trouble is that the PLC is dictating 3 different temperatures to the controller but i don't think the controller is able to meet the instructions of the PLC as when it is heating its internal heater just keeps ramping up constantly until it alarms and trips out the contactor. I have had an expert in to review the problem and he says it is not the PLC but the HMI controller on the heater unit itself but the problem is the company who made it have gone out of business so i cannot get help from them. The PLC guy did suggest putting in a controller with multi channel input so it can be regulated through the 3 different setpoints or possibly a second temperature controller. The HMI is turning on an output which is turning on a SSR which is then turning on the contactor which stays on until it trips because it doesn't know when to stop.If i try adjust the pots, or even if i disconnect the output from the HMI i get an alarm too, so it is like the relay banks ( photo below) are constantly looking for a feedback, but i cannot be sure of this because it doesnt look like they are and I have no schematics. I am just looking for some direction as to where to go with this would a different controller help that could talk back to the PLC? Or is it a second probe?

The photo attachments are of the relay controller (1 of 3) the back of the HMI input/ output terminals and the front and back of the variable temperature probe pots.