APCS Reverse Acting Relay with Long Off Delay Example

Reverse Acting Relay with Long Off Delay Example

UAP0010 - USC Application

Because the on and off delays on the relays only go up to 2330 seconds this example uses an equation to obtain a one hour delay.

If input on CH1 is below a low limit then RY1 should switch on.
If input on CH1 then goes above hi limit then a switch off timer should start.
RY1 will switch off after the switch off timer has expired as long as the input to CH1 is above the low limit (This functionality could be changed in a number of ways).

Constant	Description
Con_a	Low Limit (3)
Con_b	Hi Limit (12)
Con_c	Maximum Time (3600 for 1 hour)
Con_d	Timer not running flag value and decrement value
M4	Timer counter
Timer enable:	must be set to Y
Update on input	must be set to N
Timer period:	1 second

Command	Comment
Send M4	send timer value for debug purposes
If RY1 Goto 014	Branch if relay on.
Read Ch1	Check if
Con_a	below low
Subtract	trip
Send M4	send timer value for debug purposes
If < 0 Goto 028
Exit	----------------------
Line 014	Check if timer
Read Mem4	is running
Exit	If > 0 Goto 034
Del S
Read Ch1	Check hi limit
Con_b	if timer not
Subtract	running
If > 0 Goto 048
Exit	----------------------
Line 028:	Switch on
RY1 on	relay and
Con_d	initialise
Save Mem4	timer to not started
Exit	----------------------
Line 034	STEP TIMER
Con_d
Add
If= 0 Goto 042	Branch if time out.
Save Mem4
Exit	----------------------
Line 042	TIME OUT
Read Ch1	Check if
Con_a	below low
Subtract	trip before
If < 0 Goto 028	switching off
RY1 off	relay
Con_d
Save Mem4
Exit	----------------------
Line 048:	START TIMER
Del S
Con_c
Save Mem4
Exit	----------------------

File	Comment
Help	If unexpected results occur when loading the .usc file press back and click on help for instructions.
UAP00101.usc	First Issue.
UAP00102.usc	Convert to USC config 105 standard.

Analogue Process Control Services - The Signal Conditioning Specialist