Trying to get a Voltage Out from PID prog.

MikeLB56

Member
Join Date
Nov 2006
Location
Lancaster, Pa
Posts
14
I am trying to get a voltage output from the analog side car. the Thermocouple we are using is recognized as the program is reflecting readings. We are trying to get a voltage output proportional to the disturbance of the setpoint. We cannot Figure out why maybe this screen shot will help you help me!! THANKS
clip_image002.jpg
clip_image002.jpg
 
Greetings Mike.

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AL110606.JPG
 
Screen Shots

ok hopefully this helps....we are very stuck and have been trying for a long time....we need basically a temperature reading from the thermo into the analog and the analog to give us a 0-10V DC output based on the distance from the setpoint....see if you can help me from these pics....i can get more....thanks
 
MikeLB56 said:
ok hopefully this helps....we are very stuck and have been trying for a long time....we need basically a temperature reading from the thermo into the analog and the analog to give us a 0-10V DC output based on the distance from the setpoint....see if you can help me from these pics....i can get more....thanks

You have the scaled output Min / Max both set to 0. The MAX value should be the MAX value required to give the analog output 10VDC

scaled1.JPG
 
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Thank you for your time and that pic. It's a little more advanced than what I am now trying.

I've tried to just use SCP blocks to accomplish my short term goal of varying an output (voltage 0-10) with an input signal (thermocouple mv).

I am getting a definate input (changes with heat). Can I take my input and put it directly into my scp block and output it right to my analog output? Or do i need to do something with an N register? I actually tried both, but of late I am taking the input right from the thermocouple module into the scp function (I:2.0), scaling it down to 0-10 and it is registering values (8,6,etc). This would appear to work on the screen, but when I go to measure it with a DMM - nothing. I would like to see physical voltage across the output (O:1.0), but all I see on my multimeter is .016V????

I'm confused... My Analog module is set for Voltage (I checked this several times). Maybe I'm missing how to config the Output so that it would give me 0-10V. Please help.

Thanks in Advance.
 
How about you post your application and I will take a look.
The app I posted receives an RTD input to the PID block, the output is sent to an analog output card that uses 4-20ma to control a 3-15PSI control valve to regulate amount of steam in a heat exchanger. Your app is similair
 
Last edited:
MikeLB56 said:
I am trying to get a voltage output from the analog side car. the Thermocouple we are using is recognized as the program is reflecting readings. We are trying to get a voltage output proportional to the disturbance of the setpoint. We cannot Figure out why maybe this screen shot will help you help me!! THANKS
clip_image002.jpg
clip_image002.jpg

Is the "analog side car" a analog output module? If you are trying to use a PID I usually first SCP the input with the proper settings then put it in the PID and setup the Min and Max inside the PID and then SCP the output with the proper settings. Why couldn't you setup your PID Min and Max to 0-10.
 
You mention a thermocouple, can we assume you are using a thermocouple card that converts the milliamp signals to analog ma, either 0-20ma, 4-20ma or? You can not directly connect a thermocouple to a regular analog input.

You need to mention what devices you are using so the help can be in detail.

As mentioned you left SCP at zero, there will have to be settings there so the plc will know how to scale the output to match the input.

As mentioned it would be helpful if you offered more information.
 
the analog module is a 1762-IF2OF2 2 Chan. Input 2 Chan. Output. The thermocouple itself is a type K that reads in mV which represent temperatures. This is connected to the 1762-IT4 4-Channel Thermocouple. That is all I can give tonight. I can get more screenshots and applications tomorrow when I can get back in the Lab. I am a student at Millersville Univ. in PA so my availability of materials is limited.
Thanks so much for your willingness to help. GREATLY APPRECIATED!!!
 
If you want to control Temperature then the PID instruction is the way to go. But for testing output pre your request see below.

Below will vary your output without the PID.

Input Configuration : This gives temperature in degrees F

input.jpg


Output Configuration: This gives 0-10 Volts for 0-16383 input

output.jpg


Scaling: You can change the input min and input max to suit your needs. Below 0 Degrees=5 Volts, 500 Degrees= 10 Volts

scaling.jpg
 
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I've tried just about everything now and I am still lacking Voltage output on my analog module. This might be a silly question, but does the 1762-IF2OF2 2 Channel I/O Analog Module require an external power supply in order to output that voltage. I would think the Module would act essentially as a potentiometer. I've even exactly replicated the program that Mickey gave me. Am I missing something right under my nose????? Thanks again
 
MikeLB56 said:
I've tried just about everything now and I am still lacking Voltage output on my analog module. This might be a silly question, but does the 1762-IF2OF2 2 Channel I/O Analog Module require an external power supply in order to output that voltage. I would think the Module would act essentially as a potentiometer. I've even exactly replicated the program that Mickey gave me. Am I missing something right under my nose????? Thanks again

If you are seeing values outputed to the output register, but no voltage is measured at the card's terminals, then you have a wiring and/or hardware issues. If you see only a value of 0 sent to the output, then its a software and/or configuration problem.
 
How do I get power into the analog module? Is there a physical wiring scheme that I need to be using? If so can anyone post a schematic. I am puting up the program. We are going into the N7 register because we will bee using PID later on. We just took out everything in between. See if you can help me on the program side and physical wiring side.
 

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