adccommunitymod (AutomationDirect) asked a question.
Created Date: May 12,2014
Created By: groovydc
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Hello, It's been over 5 years since I 've worked on a PLC project from the ground up and up until today it's been going very well. The problem is that I have 2 Calex non contact temperature sensors. One with a display and one without. The one with a display is reading 90-115 degrees F (based on the display) and I have a measured 7mA coming into the F2-04AD-1 analog input card. I used the scale function to set the 4-20mA signal to 0-500 in order to match the scale I configured in the PM-MA-301-CT-CRT infrared temperature sensor controller screen. The problem is that I cannot get a reading to display in the Do-More software. Both sensors read a -125. Here is what I 've done so far: Checked connections. Verified polarity and re-wired wx0 and wx1 a couple different times. I'm still getting the same output from the scale function. It's not changing. Even when I take a piece of metal and heat it with a lighter. The display will show 200+ degrees F but the output value in the scale function doesn't change. I'm using a 9 slot base with a 205 cpu with Ethernet/usb/serial connection options. If you folks can help me get the sensor with the display working I'm positive that the other will fall in line also. Any assistance would be greatly appreciated. Included is a picture of the scale value for WX0. Sincerely, Groovy :cool:
Created Date: May 12,2014
Created by: groovydc
By the way at the time of this posting the screen readout on the IR Temp sensor is 97.5 degrees F.
Created Date: May 12,2014
Created by: scott.lawrence
your input scale isn't correct... you should have that scaled to the ADC of your module, i.e., if it's 12 bits, then 0-4095.
example...
http://i.imgur.com/EkyFuPo.png
Created Date: May 12,2014
Created by: groovydc
Ok so I changed the scale. Thing is that the input isn't changing any. I am reading about 8.2mA going to WX0 but the scaled output is still bottomed out. It should be reading somewhere around 134.6
Created Date: May 12,2014
Created by: scott.lawrence
have you done a program-to-run transition since modifying the code? Sometimes, analog modules are funny that way...
Created Date: May 12,2014
Created by: groovydc
Nope.
I 've never thought of that. I'll do it now and see what happens.
Created Date: May 12,2014
Created by: groovydc
Still bottomed out. I have even tried hooking the sensors up to WX3 and 4 and get the same feedback in the designer software.
But let's see if I got this cycle right. On the 205CPU I switch to terminal mode. Then from within the designer software I go to program mode. Wait a bit and then go back to run mode. Correct?
If that's so then we 're still at the same spot. I hope that I didn't get a faulty analog input module. But no issues are being reported so that may not be the case. It's probably a configuration issue somewhere.
Created Date: May 12,2014
Created by: scott.lawrence
ok.. barring anything else, verify the 24VDC to the module
Created Date: May 12,2014
Created by: groovydc
Ok so in order to do what you suggested do I:
1: check the voltage across the top terminals which is listed at 0 and 24V respectively.
2: Power down the PLC remove the analog in card, power it up, take voltage readings along the molex/quick connector.
Just curious.
I went ahead and did number 1 and got nothing. Thing is that I 've got an auxiliary 24V PS on the rack (Ordered it with the 9 slot rack)
Created Date: May 12,2014
Created by: scott.lawrence
Ok so in order to do what you suggested do I:
1: check the voltage across the top terminals which is listed at 0 and 24V respectively.....
I went ahead and did number 1 and got nothing.
On the module terminals, you should have 24VDC connected...
Created Date: May 12,2014
Created by: bcarlton
As Scott is saying, 24VDC must be brought by wires from a secondary power supply to the module. It doesn't get this from the backplane. It is not a good idea to use the 24VDC auxilary output from the rack power supply - too noisy.