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S7-1200 214 on board analogues

2/19/2010 2:52 PM	Rate (0)
Richard Jupp Posts: 47 Rating: (0)	Is it possible to reconfigure the onboard analogues to current rather than voltage. I recall there being a method of adding a resistor to make this possible but I can't recall how or the ohms of the resistor? Can anyone help.... Regards Richard
Richard Jupp Posts: 47 Rating: (0)
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2/19/2010 3:01 PM	Rate (1)
Giuliano Posts: 21 Rating: (14)	Hi Richard, The 2 analog inputs onboard in all CPU's of S7-1200 is to 0...10V only. You can install this resistor and son on, but I don't recommend. I recommend use the analog modules e.g.SM1234. Regards,
Giuliano Posts: 21 Rating: (14)	Last edited by: Giuliano at: 2/19/2010 3:03 PM
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This contribution was helpful to 1 thankful Users Tomy Master

2/19/2010 5:50 PM	Rate (0)
Denilson Pegaia Diamond Expert Joined: 9/23/2005 Last visit: 12/30/2025 Posts: 4435 Rating: (1487)	Hi, 10V/500Ohm = 20mA The error will be proprotional of the Resistor tolerance and the effect of the input impedance of the module in paralell: 500 Ohm // 100.000 Ohm =497,51 ohm => 0.5% addtional error
	Denilson Pegaia Siemens Industry Sector Technical Support
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2/19/2010 7:51 PM	Rate (0)
Richard Jupp Posts: 47 Rating: (0)	thank you
Richard Jupp Posts: 47 Rating: (0)
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3/24/2010 5:36 PM	Rate (0)
reimond Posts: 3 Rating: (0)	It would possible to use onboard analogs as current this way: 1. Using 500 ohm resistor (two 1k parallel) and getting voltage input 2-10V from sensor 4-20mA output 2. Then, in NORM_X function, setting minimum value to 5530 (27648*2V/10V=5529.6) instead of 0 3. After that, with SCALE_X function will scale sensor value It seems to work, but is it way to solve this problem?
reimond Posts: 3 Rating: (0)
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3/24/2010 9:15 PM	Rate (0)
Denilson Pegaia Diamond Expert Joined: 9/23/2005 Last visit: 12/30/2025 Posts: 4435 Rating: (1487)	Hi, I don't found alternative to the use of the resistor. About the mathematics, you can use the ready to use blockson the tip: https://www.automation.siemens.com/BR/tf/WW/en/Posts/31698
	Denilson Pegaia Siemens Industry Sector Technical Support
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3/25/2010 7:17 AM	Rate (0)
NLL-Stefan Posts: 3 Rating: (0)	Pegaia I don't found alternative to the use of the resistor. Hi, You can use: INTERFACE CONVERTER ON: 4 TO 20 MA OFF: 0 TO 10 V MLFB: 3RS1703-1AD00 This converts the 4 to 20mA input to 0 to 10V Output. It can't supply the sensor with current but I use this with a small workround and it works fine with my S7-1200. BR Stefan
NLL-Stefan Posts: 3 Rating: (0)
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