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CPU analog input 0-10V wiring with transducer output 4-20mA

Created by: Milosh at: 1/29/2014 2:19 PM (17 Replies)

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1/29/2014 2:19 PM	Rate (0)
Milosh Silver Member Joined: 8/16/2010 Last visit: 3/20/2023 Posts: 622 Rating: (11)	Hi all, I have the situation from the attached image. So, on first analog input is output from frequency inverter drive (0-10V), and on second analog input is output of the thermocouple transducer (4-20mA), but in parallel is connected resistor (500Ohm)... Is this good solution??? Is the 0V good conected? Attachment cpu ai.jpg (563 Downloads)

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1/29/2014 2:38 PM	Rate (0)
Marcjan Platinum Member Joined: 4/22/2010 Last visit: 12/15/2022 Posts: 5697 Rating: (702)	Hello, I would not call it a good solution, that would be using other transducer or other anlog card. But the connection is o.k. if the transduser is a 4wire type and does like the 500 ohm resistor (some can handle max 250 ohms at the load side). 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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1/29/2014 2:48 PM	Rate (0)
Milosh Silver Member Joined: 8/16/2010 Last visit: 3/20/2023 Posts: 622 Rating: (11)	Marcjan Hello, I would not call it a good solution, that would be using other transducer or other anlog card. But the connection is o.k. if the transduser is a 4wire type and does like the 500 ohm resistor (some can handle max 250 ohms at the load side). Regards, Marcjan Sorry, it's a working solution, not good :) How you determine which resistor to use??? Thank's for reply...

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1/29/2014 4:12 PM	Rate (0)
Marcjan Platinum Member Joined: 4/22/2010 Last visit: 12/15/2022 Posts: 5697 Rating: (702)	Hello, Most of the time 500 ohm will do the job, in case of trouble(or betterm before)you need to read the transducer datasheet. 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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1/30/2014 7:37 AM	Rate (0)
Milosh Silver Member Joined: 8/16/2010 Last visit: 3/20/2023 Posts: 622 Rating: (11)	Ok, I have HD778TR1 transmitter, with specification in attachement... Which resistor to use? How to connect it to PLC analog input (new 'sheme' is attached - is that good wiring)??? Attachment HD778TR1_HD978TR1_2_uk.pdf (318 Downloads)

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1/30/2014 7:38 AM	Rate (0)
Milosh Silver Member Joined: 8/16/2010 Last visit: 3/20/2023 Posts: 622 Rating: (11)	And new sheme attachement.... Attachment cpu ai.jpg (371 Downloads)

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1/30/2014 8:07 AM	Rate (0)
Marcjan Platinum Member Joined: 4/22/2010 Last visit: 12/15/2022 Posts: 5697 Rating: (702)	Hello, A 500 ohm resistor will do. I think you should connect it as per attached schematic. Regards, Marcjan Attachment cpu ai2_1.JPG (544 Downloads)
	Problem solved? Please let us know! Please no technical questions by PM, use the forum sections for your questions.
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This contribution was helpful to 1 thankful Users Milosh

1/30/2014 12:40 PM	Rate (0)
Milosh Silver Member Joined: 8/16/2010 Last visit: 3/20/2023 Posts: 622 Rating: (11)	Thank's Marcjan Everything works great...

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This contribution was helpful to 2 thankful Users S_Moderator Marcjan

1/30/2014 1:54 PM	Rate (0)
Milosh Silver Member Joined: 8/16/2010 Last visit: 3/20/2023 Posts: 622 Rating: (11)	Marcjan, one more question... Do you have some formula to calculate resistance? I think that this kind of connection (from your attachement) is voltage divider. Right? So, to determine resistance I need resistance of the transmitter? How to know that? Formula for voltage divider U2=(R2U1)/(R1+R2) where: R1 - resistance of the transmitter R2 - required resistance U1 - supply voltage (24Vdc) U2 - voltage to PLC input I think, this is right calculation: I=U/(R1+R2) where I=0,02A or 20mA so R1+R2 = 24Vdc/0,02A = 1200 Ohm From U2=(R2U1)/(R1+R2) R2= (U2(R1+R2))/U1 U2 - need to be 10Vdc R2= (10V1200Ohm)/24V R2=500Ohm Is this good calculation?
	Last edited by: Milosh at: 1/30/2014 2:04 PM
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1/30/2014 2:05 PM	Rate (0)
Marcjan Platinum Member Joined: 4/22/2010 Last visit: 12/15/2022 Posts: 5697 Rating: (702)	Hello, U=ir R=U/I You need 10V as max by 20mA. 10/0.02=500 Same formula explains why you have 2 V at 4mA: 20 mA 500 =2V The only problem can be the sensor, there are sensors that can handle max 250 ohm at load side, in that case you can't use a ~~250~~ 500 ohm resistor. Regards, Marcjan
	Last edited by: Marcjan at: 1/31/2014 11:34 AM corrected error. Problem solved? Please let us know! Please no technical questions by PM, use the forum sections for your questions.
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This contribution was helpful to 1 thankful Users Milosh

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