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S7-1200 CPU integrated analog input - source of signal

Created by: vl.roman at: 6/6/2011 4:02 PM (6 Replies)

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6/6/2011 4:02 PM	Rate (0)
vl.roman Posts: 6 Rating: (0)	Hello, is it possible to connect potentiometer to analog input of CPU? Or I need to use only sensor with voltage output. I have analog proximity sensor and I think about the simplest way how to connect it into CPU without any additional parts and I don't want to use modules. Thanks for answers.
vl.roman Posts: 6 Rating: (0)
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6/6/2011 6:38 PM	Rate (0)
FreakOnALeash Posts: 267 Rating: (24)	sorry, but you have to perform a potential divider if you wanna use the onboard AI or you need at least aSB1231 RTD (6ES7231-5PA30-0XB0) to measure resistance (maximum limit 150, 300 or 600 Ohm).
FreakOnALeash Posts: 267 Rating: (24)
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6/6/2011 10:11 PM	Rate (0)
Marko Bursic Posts: 1410 Rating: (154)	You could use 24V dc with series resistor, zener diode and capacitor. That is the cheapest solution to get reference 10V voltage.
Marko Bursic Posts: 1410 Rating: (154)
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6/6/2011 10:30 PM	Rate (0)
0_Einstein Grandmaster-Expert Joined: 7/7/2010 Last visit: 12/31/2025 Posts: 16342 Rating: (2521)	If I am reading your post correctly, you have an analog device which reads proximity to a target. If the signal from the analog deviceoutputis within the range of0-10VDC, you can use that device directly to the PLC analog input. Perhaps you could explain more about your analog proximity device's capabilities?
	science guy
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6/7/2011 9:41 AM	Rate (0)
vl.roman Posts: 6 Rating: (0)	I have proximity sensor, which has linear output - resistance from 0 to 3.7K. Some interfaces with voltage input have inside voltage source and it is possible to connect to this input resistors or voltage source. I have attached simple picture of it. And my question is if S7-1200 can handle sensors with same way. Attachment Analog interface.JPG (947 Downloads)
vl.roman Posts: 6 Rating: (0)
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6/7/2011 4:04 PM	Rate (0)
0_Einstein Grandmaster-Expert Joined: 7/7/2010 Last visit: 12/31/2025 Posts: 16342 Rating: (2521)	Yes, you can use your analog sensor. As others have posted, you need a 10V voltage source to power the Potentiometer output of the sensor (Vcc). The voltage source common should reference the PLC common and your AI signal should work fine on the PLC's onboard analog input connection.
	science guy
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6/7/2011 10:01 PM	Rate (0)
Marko Bursic Posts: 1410 Rating: (154)	From picture you posted is not clearly what kind of sensor you have, also on picture is not a potentiometer, but a variable resistor and this is an another problem. However sipmlest way would be adding a 5.6k resistor in series and 24V source, like first picture and make sure that you will not never disconnect the sensor.
Marko Bursic Posts: 1410 Rating: (154)
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