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Old February 9th, 2018, 02:13 PM   #1
Nandraj
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ControlLogix Chassis Analog Input Module issue

Dear all,
I a have issue with 1756-IF8 Module , I reading some Air pressure and temperature analog values from this card , I have total 4 Analog Input out of all One analog input Read Properly But another not reading values .If we go in properties it shows calibration Error . how can be calibration done? Card is good
Please find attachment for more clarification
please help me to resolve issue
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File Type: jpg Cooling Tower Analog card.jpg (66.9 KB, 57 views)
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Old February 9th, 2018, 02:40 PM   #2
mdim
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If you select a channel and press the "Start Calibration"button on the right you are prompted to connect Loop Calibrator(4-20mA signal) and give some levels.
But the fact that it is showing error on all channels and you say, that module is ok(Card is goood)?
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Old February 9th, 2018, 02:45 PM   #3
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Ya sir .I agree it shows error but why it reading 1 channel input . What may be the issue .
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Old February 11th, 2018, 06:14 AM   #4
daba
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1756 analog module calibration is a procedure you have to follow until the end.

You get prompted to connect a voltage or current source (input modules), or a measuring device (output modules) for each channel, recording results as you go.

Your module shows "Error" on all channels because someone, sometime, pressed the "Start Calibration" button, and didn't complete the calibration steps. The "Error" is a calibration process error, not an error with the module's current operational state.

Do not be concerned about this, none of the current gains and offsets (as shown) will be updated to new calibration values until the whole of a calibration process is successfully completed. To "resolve" it (which as I say you do not need to), you would have to successfully complete the calibration process, for which you will need a precision voltage source. Unless you have one, you can buy, or hire, but probably not cheap. In general, unless you work in a regulated industry, no-one bothers with re-calibration, and use the module for the whole of its working life with the factory calibration.

The date that the module was last successfully calibrated is stored in the module, and is shown on that tab you posted.

For your problem that one analog input is reading OK, and another is not, do the following....

Check the configuration settings for the non-working channel. Is it set to the correct input type. Are the scaling parameters correct., etc.

Check (with a voltmeter) that you are actually getting a voltage on the input of the channel that is not reading. (NB. a mA Input type will have a 250 ohm resistor across the input, such that 4 to 20mA will be 1 to 5V). If you have a voltage within range, and the channel is not reading correctly, then the channel may be faulty.

If the above checks out OK, you can try moving the non-working input to another unused channel.

If you see no voltage on the input, then your external wiring is at fault. Has it been fused ? Some people put a fuse in analog inputs, especially if it is a current input.
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Last edited by daba; February 11th, 2018 at 06:45 AM.
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Old February 11th, 2018, 06:18 AM   #5
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How is the calibration process ..If i do this calibration with this module .Will it affect controller operation ? Or shall is inhibit module ?
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Old February 11th, 2018, 06:56 AM   #6
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Quote:
Originally Posted by Nandraj View Post
How is the calibration process ..If i do this calibration with this module .Will it affect controller operation ? Or shall is inhibit module ?
Calibration of an input module requires that you disconnect your normal input signals, so that you can inject precision signals.

Obviously this will be detrimental to the process, so it should not be running at the time of calibration.

You would be advised to read the "Help", click the Help button on the Calibration tab and it takes you straight to "Start 1756 I/O Analog Module Calibration" help page. lots of information on there.

I repeat - You don't need to perform calibration, unless you have to. You can ignore the "Error" status's, they are not affecting module operation.
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Old February 11th, 2018, 09:55 AM   #7
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Yes sir ..Module running but I didn't get. The analog input values
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Old February 11th, 2018, 01:08 PM   #8
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Maybe you should first check the configuration and then if it is ok, just try to provide voltage or current source and check it reads ok. Error status, as Daba says should not affect the module's operation and it should show some values. If it shows values with the loop calibrator, than it means you have problem with the signal coming from field. If no change with the loop calibrator, consider replacing module. We had some modules burnt due to bad maintenance. If you open pg.60 of the manual :

http://literature.rockwellautomation...m009_-en-p.pdf
You can see the 249 Ohm resistor on the input(1/4Watt) If you provide 24VDC directly, it smokes out (It at least, I don't know if there is problem in the module also). Module usually shows calibration error and values are not read. We had a system where we replaced multiple modules due to bad maintenance, until we trained the guys there (and put individual fuses on the inputs).

I hope your module is alive, but you should first determine this, by providing source (loop calibrator) to each of the channels and verifying it reads correct values.
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