Instructions

UM-0085-B09 DT80 Range User Manual Page 85
RG
Alarm Digital Action Channels
One or two comma-separated digital action channels can be declared for each alarm. These channels will then mimic the
state of the alarm. That is, these outputs are set to their default state if the alarm tests false, and are set to there non
default state if the alarm tests true:
Digital action channels can be:
• digital outputs (n
DSO)
• Attn LED output (
1WARN)
• latching relay output (
1RELAY)
• channel variables (n
CV)
These will be set according to the following table:
Digital Action Channel
Value if Alarm FALSE
Value if Alarm TRUE
1..4DSO (DT80/ 82I/ 85)
1..3DSO
(DT81/ 82)
1 (high/ off) 0 (low/ on)
5..8DSO
(DT80/ 85)
4DSO
(DT81/ 82)
0 (low) 1 (high)
1WARN
0 (LED off) 1 (LED on)
1RELAY
0 (relay open)
1 (relay closed)
nCV
0.0 1.0
Typically, the digital state outputs are used to annunciate the DT80 alarm by switching devices such as relays, sirens
and lights, or to directly control actuators and similar equipment.
For example,
RA1M ALARM(4TK<-1)3DSO"Heater on^M"
will check the temperature every minute. If it drops below -1°C a message will be output and digital output 3D will go low,
energising an external heater relay. The digital output will remain low (heater on) until the temperature (measured every
minute) is no longer below -1°C.
Similarly,
RB10S ALARM(2+TC>2100)2CV,1RELAY"ReactorScram"
checks a temperature every 10s; if it exceeds 2100°C then the relay will close and 2CV will be set to 1.0 until the
temperature drops back below the setpoint. Once this occurs the relay will open and 2CV will be set back to 0.0.
Alarm Action Text
Action text may be included in an alarm command. This text string is automatically returned to the host computer and/or
logged to the internal file system and/or transmitted by email/ SMS:
• once whenever the state of a single-shot alarm (
ALARM) goes from false to true, or
• repeatedly at the controlling schedule’s rate while a repeating alarm (
IF or DO) remains true
Up to 511 characters of action text can be included in each alarm. Note however that the resultant string (after
processing any substitution characters; see Substitution Characters (P86)) may be truncated depending on its final
destination:
Destination
Max number of characters that will be output
host computer via command interface
511
LCD display 16
log file
set by
ALARMS:W
n (alarm width) schedule option
(default 60, max 245)
email
255
SMS 160
Setting the alarm message switch (P262) to /z stops the return of the action text to the host – in a similar way to the NR
(no return) channel option.
Destination for Text
Action text is normally enclosed in "double quotes", in which case it is returned to the host computer using the currently
active communication port. If, however, the action text is instead enclosed in
'single quotes', the actionText is sent
exclusively to the RS232 Host Port on the logger. This is useful for communicating with external modems when they are
in command mode and when the host port is used for other purposes.