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suggested circuit to enhance the output of analog output through high resistance

Created by: hazem at: 10/17/2010 9:04 PM (5 Replies)

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10/17/2010 9:04 PM	Rate (0)
hazem Bronze Member Joined: 2/15/2010 Last visit: 1/20/2024 Posts: 329 Rating: (6)	Dear Expert, i have analog ouput voltage around 1.5vdc connected to load via Slip Ring to feed proportional valve once i connected the voltage to proportional valve the voltage drop at proportional valve to 1.15vdc but at ouput of plc its remain constant 1.5vdc i try to connect normal voltage follower but not use same situation. for your information the slip ring resistor varies depend on the brush connection may be 10 ohm or 100 ohm or less or may be 300 ohm so i search any body know any circuit to enhance this situatio. when i connect the proportional valve without Slip Ring the voltage remain as it is without any change. i hope your fast help. Regards
	Hazem
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10/18/2010 10:25 PM	Rate (0)
Ben Rad Bronze Member Joined: 7/28/2010 Last visit: 8/31/2024 Posts: 184 Rating: (11)	Hazem, You better use a signal isolator. Take a look atthe MINI Analog signal isolatorsfrom Phoenix Contact. Regards, Behnam www.sigmaprocess.ca

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10/18/2010 11:19 PM	Rate (0)
hazem Bronze Member Joined: 2/15/2010 Last visit: 1/20/2024 Posts: 329 Rating: (6)	Dear Behnam; thanks for your reply i knew i need to use siganl isolator but i need to construct this manually right now idon't need to wait tell buy this i need to enhance my system by something then i can think to buy new siganl isolator. Regards
	Hazem
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10/20/2010 9:00 PM	Rate (0)
jklm Platinum Member Joined: 12/22/2006 Last visit: 1/25/2022 Posts: 1742 Rating: (308)	Hello, Is it possible for you to use a current signal instead of voltage output? Let say that without slip ring you measure a current of 10 mA running trough the valve when you apply 1,5VDC. Now you use an analog current output instead of a voltage output and you let the current output deliver 10 mA. The analog output normally will adapt its output voltage to keep the 10 mA in the circuit even with slip ring (in other words with a variable resistance in the loop).
	Best regards jklm Suggestion was helpful? Feel free to rate it.
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10/25/2010 5:18 PM	Rate (0)
hazem Bronze Member Joined: 2/15/2010 Last visit: 1/20/2024 Posts: 329 Rating: (6)	Dear Sir, you mean that i have to change my valve to workwith 4 to 20mampsinstead of 0 to 10vdcor what you mean exactly? i already added one capcitor parallel with signal of proportional and there is too much advance but it shwon now 1.41 from 1.5vdc. and i still need your comment to understand your ideas well.
	Hazem
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10/27/2010 7:52 AM	Rate (0)
hazem Bronze Member Joined: 2/15/2010 Last visit: 1/20/2024 Posts: 329 Rating: (6)	Dear All, After i fully understood the problem i found the better for me in this situation specailly when signal transferred with long distance and or high resistance to use 4 to 20mamps instead of 0 to 10vdc because of the board with give current refrence with regardless resistnace inside the way so i am searching now to find out board to convert from voltage to current then from current to voltage again otherwise i have to change the proprotional valve to work form 4to 20maps insead of 0 to 10vdc. Regards,
	Hazem
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