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Problem in Analog input card

Created by: venugopal at: 10/4/2008 7:32 AM (20 Replies)

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10/4/2008 7:32 AM	Rate (0)
venugopal Posts: 12 Rating: (0)	In one of my project i am using S7-300 Analog input module part no:6ES7331-7KF02-0ABA0.In this there is a position feedback transducer which is of 4 wire type.From the transducer i am getting 4-20ma signal properly,But in analog input module it is showing continiously overflow(the value of pheripheral input is 32767 which i have monitored in VAT table).But for the all other analog input signals which is of 4 wire i can read the proper values. So while checking this i found the voltage across the 4 wire tranducer terminals which is working properly is nearly 24Volts. But the voltage across the 4 wire position feedback tranducer which is not working is of 28v. How to resolve this problem? Regards, Venugopal.T
venugopal Posts: 12 Rating: (0)
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10/4/2008 4:21 PM	Rate (0)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 10/10/2024 Posts: 12285 Rating: (2685)	Hello venugopal; The 6ES7 331-7KF02-0AB0 module is capable of measuring current in boith 2-wire and 4-wire configurations, but the selector module (on the outside of the physical module) must be set to "D" for 2-wire measurements, and to "C" for 4-wire connections. Of course the hardware configuration of the analog module channelmust be done correctly in the HWConfig editor. This is shown in the S7-300 Module Data manual: Measuring range Measuring range module setting 2-wire transducer 4 mA to 20 mA D 4-wire transducer± 3.2 mA C ± 10 mA 0 mA to 20 mA 4 mA to 20 mA ± 20 mA Tell us if this corrects the issue. If not, we'll look for other problems. Hope this helps, Daniel Chartier

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10/4/2008 4:44 PM	Rate (0)
venugopal Posts: 12 Rating: (0)	Dear Daniel, I have done a setting in selector module to C for 4wire connection and in hardware configuration also the settings are properly configured.I checked this particular channel (used for position feedback)with analog injection (4-20ma)kit.I also checked with another 4-20ma 4 wire flowmeter signal in this channel.In bothe the cases I can able to read the values in PLC.But the problem is when i connect this 4wire position feedback signal the pheripheral input is showing 32647 and it is also affecting other pheripheral inputs in the same analog input module. Regards, Venugopal.T
venugopal Posts: 12 Rating: (0)
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10/5/2008 8:11 AM	Rate (0)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 10/10/2024 Posts: 12285 Rating: (2685)	Hello venugopal; If your channel is operating correctly with a flowmeter signal, and with a 4-20 mA simulator, but not with the position feedback transmitter, it could well be ythis transmitter is not wired properly or deficient. You have measured 28 V at the transmitter outlet, you say? What is the type of instrument you are using for analog position signals? Some kind of magnetorestrictive sensor (Temposonic)? or some type of resolver? Here are a few suggestions: Check the sensor's power supply, grounding and cabling first (re-examine the sensor's dtasheets and connection diagrams to make sure it is well cabled).. Once that is validated, try connectingit on other channels of your analog input card to see if it shows the same problem. Use a multimeter to read the mA signal coming from the sensor at different signal levels. Please come back to us with the results of this investigation. Hope this helps, Daniel Chartier

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10/5/2008 8:26 AM	Rate (0)
venugopal Posts: 12 Rating: (0)	Dear Mr.Daniel, Position feedback transmitter wiring is properly connected and i can measure 4-20ma in multimeter also.But when i connect it to AI Card in PLC and read this channel inVAT table i am continously reading 32647 in this particular pheripheral input even the current is changed from 4-20ma. Regards, Venugopal.T
venugopal Posts: 12 Rating: (0)
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10/5/2008 8:53 AM	Rate (0)
UMENCHO Diamond Member Joined: 3/21/2006 Last visit: 10/7/2024 Posts: 10229 Rating: (1181)	Hi you can try to disconect other chanel and connect only this transducer to this card. Or try to connect to different chanel. regards

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10/5/2008 9:39 PM	Rate (0)
CHAPs Member Joined: 10/5/2008 Last visit: 9/21/2023 Posts: 4 Rating: (1)	Dear UMENCHO, Please go to the field and also check that if there is an AC wiring Moving along the Analog Input Field Wiring through the ducts. In your eariler Post you have already tested the card and corrected the channel. The problem only occurs when there is Field and Instrument Involved. TheMumtimeter is not that sensitive as the AI card so the Harmonicscan effect. Even of thereis a big motor near by the AI field wring the Magnetic Interference can give problem. Also for furthur check Please take that4 wire transmitter outof field into a LAB or some seperate place and thencheck it with card using a standard 24 volts supply. If the problem persists then the transmitter has some problem if not then clearly its a field Harmonics problem or Wiring shortproblem etc.
	------------------ Regards, Umar Samad Abu Dhabi Polymers Company Co. Ltd. (Borouge)
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10/7/2008 10:10 AM	Rate (0)
venugopal Posts: 12 Rating: (0)	Dear Umar, There is a seperate duct for power cable and control cable. Regards, Venugopal.T
venugopal Posts: 12 Rating: (0)
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10/8/2008 4:51 PM	Rate (0)
Ayman Elotaify Platinum Expert Joined: 5/28/2008 Last visit: 10/7/2024 Posts: 4515 Rating: (839)	Hi venugopal, Do you use shielded cabels? Did you connect the shield with the ground? Please tell us as you have said that the value of this AI channel affect the other channels of the same module. and this means that your problem that you have noise affect the AI reading. Regards,
	Ayman Elotaify
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10/8/2008 6:53 PM	Rate (0)
SteveA Posts: 297 Rating: (41)	When the input card is configured for current input, there is a 25 ohm resistor across the input terminals to sense the current. If 24 volts is applied directly to the input accidentally (miswired or short circuit), this resistor will be destroyed. If this happens, you will always get a maximum value reading in software. You should be able to check this with an ohmmeter, especially by comparing to a working channel. If it is damaged, you will need to replace the module. Hope this helps, SteveA
SteveA Posts: 297 Rating: (41)
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