adccommunitymod (AutomationDirect) asked a question.
Created Date: July 28,2010
Created By: rgrant8584
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hello,I am setting up a loadcell to controlle unwind load but i can not scale the negative number loadcell are 0-300 lbs the high side is fine i can scale that,but i can not scale low side PLC 260 // Rung 92 // Address 738 #BEGIN COMMENT "line 92 and 93 are for negative numbers from load cell (0=0 -10v= 4095) " #END STR SP1 LD V1500 ANDD K7fff OUT V34030 AND V1500 K8001 OUT C63 // Rung 93 // Address 746 STR SP1 LD V34030 INV ADDB K1 OUT V34032 // Rung 94 // Address 751 STR SP1 ANSCL V34030 K1500 K0 V34034 // Rung 95 // Address 778 STR SP1 LD V34044 OUTD V34050 // Rung 96 // Address 781 END // Rung 97 // Address 782 NOP
Created Date: July 28,2010
Created by: JoeW
Have you considered converting to a real number after you read in your analog value? It will let you operate in negatives.
Created Date: July 28,2010
Created by: rgrant8584
no i have not this is the 1st time i have used negative numbers so i will try it.
i can get the negative number but just cant scale it
Created Date: July 28,2010
Created by: Do-more PE
You might want to look at EP-MISC-011 in the Example programs section of the Technical Support website.
Created Date: July 28,2010
Created by: rgrant8584
hello, i am not trying to zero this val. what i need to do is controle the output val.to the unwind brakes, i have 2 loadcell with a 90lb roller on them
val.=600 now when the mach start up roll are out of round, loadcell goes high then goes low,so when it goes low that negative has to tell the pid that it low not high (must have more air not less)
Created Date: July 28,2010
Created by: bcarlton
Add enough to your received reading to shift to all positive. The proceed with calculations.
e.g. signal -5 to + 5, add 5 to get 0 - 10
Created Date: July 28,2010
Created by: bcarlton
How is the signal from the loadcell being received?
What is the range of the raw values?
In what format are they being received? (BCD, Binary)
Created Date: July 29,2010
Created by: rgrant8584
I am using a strain amp. then it output -10 to +10 to analog card i am using Binary. no load on cells, input is 750 running load is around 2500
Created Date: July 29,2010
Created by: bcarlton
What is the received binary input when it goes negative? Are you saying that the signal drops to a low value then continues below 0? Or does it possibly go so high that the top most bit (bit 15) is set?
Exactly which CPU and analog card are you using?
Created Date: July 29,2010
Created by: rgrant8584
yes at startup it will go high and low the full scale is 0 to 8001 i got the negative to come up but when i try to scale it, it goes back to a postive number , i tryed using the ibox.with out scaling it work great
Created Date: July 29,2010
Created by: Tom Jenkins
yes at startup it will go high and low the full scale is 0 to 8001 i got the negative to come up but when i try to scale it, it goes back to a postive number , i tryed using the ibox.with out scaling it work great
8001 to me indicates a loss of signal bit is set. Are you sure your analog card is set up to accommodate +/- signals?