1769-IF16C module

ddeshi2

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Join Date
Dec 2010
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Baton Rouge
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Hi all, I'm using a Compactlogix PLC with 1769-L32E processor, 1769-IF16C, 1769-OF8C input and output modules.I'm using RSLOGIX5000 to develop the program. It is a 12-bit system. I'm configuring all the input channels to " scaled for PID". I'm using PID instruction in my program and trying to configure it.My question is what should I enter in the fields of Unscaled Min. and Unscaled Max. for PV. Is it 0-16383 or 0-4095? One of my friends told me that as it is a 12 bit-system and my channels are "scaled for PID" I should enter 0-4095 And if it is a 32-bit system it would be 0-16383. Is he right? Should I enter 0-4095? Please help.

Thank you,

Ding
 
@Sthompson

So, is it 0-16383 even for 12-bit system? Please help

ThankYou!

Ding

Don't get hung up on how many Bits it is, just read the Manual. Allen Bradley should know how it works. ;)

The Table on Page 4-33 (PDF 115) might be a little more helpful for the OF8C.
 
@ all

Thank you!

@Zhoudq

I'm trying to scale my readings of the pressure transmitter (4-20 ma to 0-750psi)for displaying on to the HMI. I'm using 1769-IF16C analog module and SCL instruction. What will be my Input Raw Max. and Input Raw Min. values? Will it be 0-4096 or -32767 to 32767? In the manual it was given as -32767 to +32767 but I'm not sure whether it is for 12bit system or not. Can you please help me with it.
attachment.php


1769.jpg
 
Raw data depends on how you have configured the card. Your picture above shows the choices. So how have you configured it? 0-4095 is not one of them.
 
@Mickey

This is not the manual that came with my PLC. I have lost the manual and when I searched online I found this. I don't think it is for a 12bit system. I have a compactlogix 12 bit system. I have configured 4 of my input channels as 4-20ma,60HZ, Raw/Proportional data. I want to display my Pressure transmitter readings (0-750psi) on the HMI and for displaying I need to scale the values. I'm using SCL function block for scaling. What would be my Input Raw Max and Input Raw Min values. Will it be 0-4095 or -32767 to 32767? Please help.

Thank you!
Ding
 
Agree with sthompson, don't care about the bits !

As you may see in the table you posted, configuring the module as 4-20 mA input and RAW/Proportional data, it will return values using the following considerations:

3,2 mA = -32767
21 mA = 32767

The full range of raw/proportional counts (-32767 to + 32767) applies to the full range, not the normal operating range for an input. While the normal operating range of a 4-20mA current input is 4-20mA, the full range is actually 3.2-21mA. As a result, a 4mA raw/proportional input channel will actually read around -29800, not -32767.

Hope this clears things,

- fuzzy logic
 
See picture below for data format values. I would use the scaled for PID or engineering units myself.

DataFormat.jpg
 
@ all

Thanks for the help.
@ Mickey,fuzzylogic

How did you come up with -29,822 to 29,085. Is it just by following the manual or is there any calculation involved?

Thank you!
Ding
 
Ding, manual gives you the needed value... anyway you may calculate those values, using a formula.

Here below a scaling formula you may use.

  • In = Input value
  • InRawMax = Maximum attainable input value(21 mA)
  • InRawMin = Minimum attainable input value (3.2 mA)
  • InEUMax = Maximum scaled value(32767)
  • InEUMin = Minimum scaled value(-32767)
Example 1: want to know which value corresponds to 4 mA

(4-3.2)x(65534/17.8)+(-32767)
0.8 x 3681.7 -32767
-29821.64

Example 2: want to know which value corresponds to 20 mA

(20-3.2)x(65534/17.8)+(-32767)
16.8 x 3681.7 -32767
29085.56

- fuzzy logic

scaling.JPG
 
Last edited:

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