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0-10V analog input.

Created by: Chehombing at: 5/8/2012 3:50 AM (10 Replies)

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5/8/2012 3:50 AM	Rate (0)
Chehombing Posts: 98 Rating: (4)	Hi, I got problem analog input in CPU module S71200. Measuring Value always jumping, but Measure with Volt meter and mA meter is stable. there press transmitter 4-20, but i make a resistant 5K ohm to convert 0-10V. Please any some suggestion..? Cheers.
Chehombing Posts: 98 Rating: (4)
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5/8/2012 8:23 AM	Rate (0)
Darius Platinum Expert Joined: 9/28/2005 Last visit: 12/10/2024 Posts: 2957 Rating: (243)	Chehombing Hi, I got problem analog input in CPU module S71200. Measuring Value always jumping, but Measure with Volt meter and mA meter is stable. there press transmitter 4-20, but i make a resistant 5K ohm to convert 0-10V. Please any some suggestion..? Cheers. Multimeter makes averaging of a value so you'll never see jumping. Use osciloscope to see jumps. In your case it might be lots of issues: frequency converter is near, alanog signal wires are near high power cables, it may be also some incorrect welding (if any) of the wires niear resistor and so on.... It highly depends on where resistor is installed, what lenght of a cable and is there any noise source near.
	Best regards, Darius
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5/8/2012 8:26 AM	Rate (0)
koenb Silver Member Joined: 6/26/2009 Last visit: 11/27/2024 Posts: 122 Rating: (23)	Hi , I believe that your analog input will overflow or the sensoroutput will saturate. U = I x R , 0.02A x 5000ohm = 100V !!! You should use a 500 Ohm ( 499 is a standard E96 series resistor ) Also check ground connections of your system if still unstable. koenb

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5/8/2012 8:31 AM	Rate (0)
Darius Platinum Expert Joined: 9/28/2005 Last visit: 12/10/2024 Posts: 2957 Rating: (243)	koenb Hi , I believe that your analog input will overflow or the sensoroutput will saturate. U = I x R , 0.02A x 5000ohm = 100V !!! You should use a 500 Ohm ( 499 is a standard E96 series resistor ) Also check ground connections of your system if still unstable. koenb I suppose original user mistyped 5k, because as you said it will give 100 V On the other hand if sensor power source is 24V I don't believe it will give 100V out of nowhere
	Best regards, Darius
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5/8/2012 8:48 AM	Rate (0)
koenb Silver Member Joined: 6/26/2009 Last visit: 11/27/2024 Posts: 122 Rating: (23)	Indead , the value where it will saturate is related to the sensor-supply. In the sensor- specifications , there is generally a maximum resitance given. If the current trough the resistor becomes to high , there is no voltage left to feed the 2-wire sensor. Nothing more than Ohm's law.

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5/8/2012 7:48 PM	Rate (0)
Tomy Master Gold Member Joined: 5/4/2009 Last visit: 11/23/2024 Posts: 914 Rating: (40)	Please consider using signal filter and isolater... Have luck
	Aim Higher
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5/9/2012 7:34 AM	Rate (0)
Darius Platinum Expert Joined: 9/28/2005 Last visit: 12/10/2024 Posts: 2957 Rating: (243)	Tomy Master Please consider using signal filter and isolater... Have luck Do you really think ? Normally we don't use it, it is enough just to correctly connect with correct cable which has screen. And don't put in the same tray as power cables. Normally it is enough. Furthermore, you could make software signal filter. Also, on some analog modules you can set up filter. About hardware filter... well in some cases it could be maybe ok.
	Best regards, Darius
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6/7/2012 4:14 AM	Rate (0)
Chehombing Posts: 98 Rating: (4)	I have been measuring with Multimeter, voltage is stable. I think analog channel is not working properly... this Analog included with CPU... So, i want to try filtering by hardware... Thanks for suguestion all
Chehombing Posts: 98 Rating: (4)
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6/7/2012 3:31 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 1/24/2025 Posts: 15558 Rating: (2468)	Chehombing I have been measuring with Multimeter, voltage is stable. I think analog channel is not working properly... this Analog included with CPU... So, i want to try filtering by hardware... Thanks for suguestion all Did you already replace the 5K resister across the input termnals with a ~500 Ohm so it stops being 10 times as sensitive to changes?
	science guy
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6/8/2012 2:39 AM	Rate (0)
Chehombing Posts: 98 Rating: (4)	yes...actually the resistant is 500 ohm.
Chehombing Posts: 98 Rating: (4)
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