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Deviation alarm with sensing of signal(s) drop out

UAP0007 - USC Application

Operating Description

  1. If the input to CH1 is below dropout then RY1 is OFF.
  2. If the input to CH2 is below dropout then RY2 is OFF.
  3. If CH1 and CH2 are within the deviation level then RY1 and RY2 are ON, this is the no fault condition.
  4. If inputs are above dropout and they are more than the deviation apart then the higher of the two inputs are OFF.






Declarations


USC Component Eng. Unit/Label Description
Constant
Con_a Dropout level (4, user specified)
Con_b Deviation level (2, user specified)
Con_i Relay On value (1, fixed value)
Con_j Relay Off value (-1, fixed value)
RY1, RY2 Trip points for the relays can be any values between -1 and +1.

Program List


Program List Comment
Read CH1 Read CH1 and CH2 to determine difference
Read CH2
Subtract
Save Mem6 Save difference in Mem6
Save Mem6 Save difference in Mem6
Del S Delete stack, this is equivalent to pressing clear on calaulator. This is done to prevent possible stack overflow and makes the equation easier to read in the simulator.
Read CH1
Gosub ChkCh1Lo Check if CH1 is below dropout value
Read CH2
Gosub ChkCh2Lo Check if CH2 is below dropout value
Read Mem4 A deviation test is only required if either CH1 or CH2 are above the drop out values. The following lines check if above dropout by testing the values in Mem4 and Mem5, if either is above 0 then the deviation test is performed at line DevTest.
If > 0 Goto DevTest
Del S
Read Mem5
If > 0 Goto DevTest
Goto SendExit If both M4 and M5 are below 0 then the program will continue to this point.LAB: SendExit is the general exit point. The Exit command on the next line is never executed and has been added for clarity.
Exit -----------------------------------
LAB: ChkCh1Lo TEST if CH1 is below Con_a
Con_a
Subtract Subtract 'Con_a' from CH1
If < 0 Goto Ry1Off Go to line Ry1Off if CH1< Con_a
Del S
Con_I
Save Mem4 Save Con_i in Mem4
Del S
Return Go back to last gosub command
-----------------------------------
LAB: Ry1Off
Del S
Con_j
Save Mem4 Save Con_j in Mem4
Del S
Return Go back to last gosub command
Exit -----------------------------------
LAB: ChkCh2Lo TEST if CH2 is below Con_a
Con_a
Subtract Subtract 'Con_a' from CH2
If < 0 Goto Ry2Off Go to line Ry2Off if CH2 < Con_a
Del S
Con_I
Save Mem5 Save Con_i in Mem5
Del S
Return Go back to last gosub command
Exit -----------------------------------
LAB: Ry2Off
Del S
Con_j
Save Mem5 Save Con_j in Mem5
Del S
Return Go back to last gosub command
Exit -----------------------------------
LAB: DevTest The Deviation Test checks if the difference between CH1 and CH2 are within the deviation value Con_b.
Del S
Read CH1
Read CH2
Subtract
ABS CH2 is subtracted from CH2 and the sign removed,
Con_b 59
Subtract Con_b is then subtracted.
If < 0 Goto SendExit If the value left in the calculator stack is < 0 then CH1 is within the deviation value of CH2, Mem4 and Mem5 already hold the correct values to control the relays and the program will jump to the exit point at LAB: SendExit
Del S
Read CH1 The Deviation Test Failed as the value left IS NOT < 0 then CH1 and CH2 are outside the deviation value, the program will continue to this point. Determine if CH1 > CH2 or CH2 > CH1 and switch OFF the appropriate relay.
Read CH2
Subtract
If > 0 Goto Rely1Off
Con_j CH2 is > CH1
Save Mem5 Save Con_j on Mem5
Goto SendExit Goto exit
Exit ----------------------------------
LAB: Rely1Off
Con_j
Save Mem4 Save Con_j on Mem4
LAB: SendExit General program exit point. Used to send the values in MEM4, MEM5 and MEM6 to the computer adaptor. The module will function without these commands, they have been included to monitor the values in these locations while testing.
Send M4
Send M5
Send M6
Exit -----------------------------------

USC Programs


File Comment
Help If unexpected results occur when loading the .usc file press back and click on help for instructions.
UAP00071.usc First Issue.
UAP00072.usc Convert to USC config 105 standard.

Analogue Process Control Services - The Signal Conditioning Specialist