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S7-300 Analog Input Module 4-20mA not reading properly

Created by: minerman at: 4/14/2013 1:37 AM (7 Replies)

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4/14/2013 1:37 AM	Rate (0)
minerman Posts: 8 Rating: (0)	Hello, I have an: Analog input module SM 331; AI 8 x 12 bit;(6ES7331-7KF02-0AB0) I have 4 channels that are set up for 2-wire 4-20mA signals. HW config is set and the jumper on the side of the module is set to "D". The 4 channels are wired to a current source. When I hook a multimeter to the source, I see 20mA DC. When I hook a source up to a channel, it reads around 13mA. Even when the source is set to transmit 4mA, or anything in between, I always see 13mA. If I disconnect the source from the card, I read about 54mA out of the card. Anybody know what I'm doing wrong?
minerman Posts: 8 Rating: (0)
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4/14/2013 7:28 AM	Rate (0)
S7 AUTOMAN Posts: 515 Rating: (56)	Hi minerman, Did u configure the measuring type(type fo signal to be measured) in the properties of the AI module in the hardware configuration?(Kindly find the attached file for your reference) How did you wire the instrument to the channel? Is it loop powered? Attachment AI Hardware Config.pdf (1346 Downloads)
S7 AUTOMAN Posts: 515 Rating: (56)	Last edited by: shazin at: 4/14/2013 7:29 AM
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4/14/2013 2:37 PM	Rate (0)
minerman Posts: 8 Rating: (0)	I don't have my program with me at the moment. But, I believe it is configured properly. I have it set up for 2-wire current 4-20mA and the switch setting to D. There is no other configuration required, right? The device is not loop powered. The device supplies its own power. 2 wires directly to the module. I think maybe this is the wrong module for a device that supplies its own power?
minerman Posts: 8 Rating: (0)
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4/14/2013 3:34 PM	Rate (0)
S7 AUTOMAN Posts: 515 Rating: (56)	Hi minerman, Kindly find attched the wiring details for the same. You need to provide the loop power for the instrument and give it a try. Attachment AI Module.pdf (953 Downloads)
S7 AUTOMAN Posts: 515 Rating: (56)
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4/14/2013 6:58 PM	Rate (0)
minerman Posts: 8 Rating: (0)	The transducer is wired as shown in the diagram. + from transducer to terminal 2 on the IO module, - on the transducer to terminal 3. The tranducer itself supplies voltage. It seems like the input card is also supplying voltage. I think this is why my current is not being mesured properly. In other words, my device is not passive. I think this may be the problem? Can someone confirm? Thanks.
minerman Posts: 8 Rating: (0)
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4/14/2013 7:21 PM	Rate (0)
Marcjan Platinum Expert Joined: 4/22/2010 Last visit: 5/3/2024 Posts: 5697 Rating: (715)	Hello, Yes,good thinking. Your sensor has it's own powersuply so it's 4 wire. Connect and setup as 4 wire and it should work. Regards, Marcjan
	Problem solved? Please let us know! Please no technical questions by PM, use the forum sections for your questions.
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4/14/2013 7:23 PM	Rate (0)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 10/5/2024 Posts: 12283 Rating: (2685)	Hello minerman; If your device provides power, its connexion must be as a 4-wire instrument. Hope this helps, Daniel Chartier
	Last edited by: dchartier at: 4/14/2013 7:24 PM Sorry, it seems Marcjan and I replied together. But since the answer is the same, you should find comfort...
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4/16/2013 8:01 AM	Rate (0)
THACDINI Experienced Member Joined: 12/1/2011 Last visit: 8/8/2024 Posts: 10 Rating: (0)	Dear Minerman, For your reference, you can use S7 300 Module Data Manual. This is a part of the S7 300 documentation package with order number 6ES7 398-8FA10-8BA0 . You can find this by searching on interent. Refer page No 345 you will find the correct wiring diagram for two wire and four wire. As mention above, you have to use four wire method of wiring. As per your information there are two terminals to power the sensor, also another two terminals for sensor signal. 1) If you are using seperate power supply, dont forget to common 0 ( V ) wires of power supply and PLC power supply. 2) Positive signal wire of the sensor, you can connect directly ONLY to module. 3) Negative terminal of the sensor, you have to connect to module, Mana ( 11 ), and COMP ( 10 ). 4) For four wire method, you have to use " C " measureing range module setting. Set correct setting for the channel, which is you are using. if wiring is ok now check your hardware configuration 5) Then Select AI module on the harware configuration, and right click go to "Object Properties". Set as " Four Wire Current " and select 4 - 20 mA. Please check try those, you may find the error . If you are success, please don't forget to give the results. Thank You.

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