Help - Search - Members - Calendar
Full Version: analog channel noise
Forums.MrPLC.com > PLCs and Supporting Devices > Allen Bradley
escski
I hope someone can help me out here....I have a system 5/03 of which is connected an analog card 1746-NI8 on one of the channels I am measuring resistance the range is 1- 10 ohms, however when I try to scale the input through the SCP instr... the counts are not stable at all ,,, I then measure the input voltage coming in from the resistance meter and its rock solid.... I thought I was picking up noise on the analog input but as I stated the voltage is solid..... I don't know where the noise would be coming from..... any ideas would be greatly appreciated.... note: the other channels are noisy as well...
TWControls
Can you post a sketch of how you have your modules wired? These are 4-20mA
Mickey
QUOTE(TWControls @ Sep 30 2008, 03:49 PM) [snapback]74097[/snapback]
Can you post a sketch of how you have your modules wired? These are 4-20mA


Looks like there dip switch selectable voltage or current. (see pdf below)
But you are right, how he has it connected or what he has connected is confusing.
A drawing would help.
TWControls
Mickey, what PDF creator do you use, for some reason I can only open up about half the PDFs you post. But you are correct, my mistake
escski
all inputs are connected as differential, and are config as 0-10v, there is one channel that is not connected and is not Jumpered , I wonder if that would have any effect.
TWControls
So where are you getting your power from? What do you have hooked to the + and -?

Provide a sketch if you can.

Also, if you put a voltmeter across the + and - of a particular channel, do you see this fluctuation? Is the reading what you expect?
Mickey
QUOTE(TWControls @ Sep 30 2008, 04:06 PM) [snapback]74099[/snapback]
Mickey, what PDF creator do you use, for some reason I can only open up about half the PDFs you post. But you are correct, my mistake


The one above was created by PDF995. But sometimes I use CutePDF writer. I have had complaints about CutePDF though.
finfin
How much are the counts varying? all meters have dampening or filtering. Maybe you need to add filtering. You might try putting a scope on it if one is available. A capacitor in your circuit might help also.
This is a "lo-fi" version of our main content. To view the full version with more information, formatting and images, please click here.
Invision Power Board © 2001-2010 Invision Power Services, Inc.