PID Heating Applicaton using a ML1400

[randy741985]

I have a PID Heating Applicaton using a ML1400. I want to bring the PV Type K thermocouple into the PID scaled for PID 0-16383. Then I want to Scale that same Input For EU in degrees. According to the Thermocouple Input Card Documentation the card Specs the Type K T.C. -454 to 2498 Fairnheit. I want to use the SPS in the PID.This Is where my question comes in, Should I Set the SPS Min to -454 and the SPS Max to 2498 in the PID. Is this the typical method? If not what is?




Thanks in advance

 

[Mickey]

As far as the Set-Point scaling what you posted should work. See below for what the manual has to say.
This allows you to enter your set-point in engineering units. ( My preferred method)

Inputs

Setpoint SP

Type a value between 1-16383, or within valid scaled range

The desired control point of the process variable. Enter this value via your ladder program to the third word in the control block (word 2).

Setpoint Max
(Smax)
Type in a value. (With 5/02 controllers the valid range is from -16383 to +16383. With the 5/03, 5/04, and 5/05 controllers the valid range is -32768 to +32767.)

If the setpoint is to read in engineering units, this corresponds to the value of the setpoint in engineering units hen the control input is 16383.

Setpoint Min (Smin)

Type in a value. (With the 5/02 controller the range is from -16383 to +16383. With the 5/03, 5/04, and 5/05 controllers the valid range is from -32768 to +32767.)

If the setpoint is to read in engineering units, then this parameter corresponds to the value of the setpoint in engineering units when the control input is zero.

Process Variable PV
(Read-only)
This is the scaled value of the Process Variable (the analog input). Without scaling, the range of this value is 0–16383. Otherwise, the range is minimum scaled (word 8) to maximum scaled (word 7).

Of course there are other parameters you are going to have to address.

 

[leitmotif]

Be very careful with Thermocouple and AC power conductors. The AC EMI can throw off the TCs. Keep them as separate as possible. Learned this the hard way.

Dan Bentler

 

[randy741985]

I was concerned about the Smin -454 I have seen this set at 0. But my understanding of the T/C card Documentation it scaling should be -454 to 2498. I had started a previous post the true range of a T/C which was related to this Question.

 

[Mickey]

I was concerned about the Smin -454 I have seen this set at 0. But my understanding of the T/C card Documentation it scaling should be -454 to 2498. I had started a previous post the true range of a T/C which was related to this Question.

Test it to prove it to yourself. Configure it as shown and then connect a thermocouple, take a reading at room temperature then heat it up to see how accurate it is. Or if you have test equipment to simulate a thermocouple, use that. Seeing believing.

 

[randy741985]

Test it to prove it to yourself. Configure it as shown and then connect a thermocouple, take a reading at room temperature then heat it up to see how accurate it is. Or if you have test equipment to simulate a thermocouple, use that. Seeing believing.

Yes I can parallel a milivolt signal with a loop calibrator to two channels 1 0-16383 the other in EU.

Thanks Mickey

 

[tracer]

I could be wrong but what the spec's are saying is that a k-type TC reads from -454 to 2498 degrees, if your not going that cold, or that hot, then you can set your min and max as you need them.