Appendix A: Alarm Functions - Extech Instruments 48VTR User Manual

Appendix A: Alarm and Timer Selections
To select an Alarm function use the 3
available settings '00' to '11' are described below. To set an alarm setpoint use 'A1SP' in the
st
1 Menu Level. To set a time for an event or soak timer, use 'time' in the 1
'00' Deviation High Alarm The actual Alarm setpoint equals the Main Controller Setpoint (SV) plus the 'A1SP'
setting. For example, if SV = 400 and A1SP = +10 then the Alarm relay will trip when the temperature rises
above 410 (400 + 10 = 410).
o
'01' Deviation Low Alarm For a Deviation Low Alarm, the actual Alarm setpoint equals the Main Controller
Setpoint (SV) plus the 'A1SP' setting. For example, if SV = 400 and A1SP = -10 then the Alarm relay will trip
when the temperature falls below 390
'02' Process High Alarm Relay trips when the process (PV) exceeds the 'A1SP' value.
'03' Process Low Alarm Relay trips when the process (PV) falls below the 'A1SP' value.
'04' Deviation High Alarm with Standby Sequence Same as the Deviation High Alarm but no relay action takes
place until the process PV reaches the setpoint for a second time. Also known as "Startup Inhibit" and is useful
for avoiding alarm trips during startup.
'05' Deviation Low Alarm with Standby Sequence Same as the Deviation Low Alarm but no relay action takes
place until the process PV reaches the setpoint for a second time. Also known as "Startup Inhibit" and is useful
for avoiding alarm trips during startup.
'06' Process High Alarm with Standby Sequence Same as the Process High Alarm but no relay action takes
place until the process PV reaches the setpoint for a second time. Also known as "Startup Inhibit" and is useful
for avoiding alarm trips during startup.
'07' Process Low Alarm with Standby Sequence Same as the Process Low Alarm but no relay action takes
place until the process PV reaches the setpoint for a second time. Also known as "Startup Inhibit" and is useful
for avoiding alarm trips during startup.
'08' EVENT ON-Timer Upon power-up the alarm is de-energized. When the PV = SV the alarm relay remains
de-energized. When the timer counts down to zero, the relay energizes. Set the timer at parameter 'time' in the
1 Menu Level. See Table below.
st
'09' EVENT OFF-Timer Upon power-up the alarm relay energizes. When the PV = SV the alarm relay remains
energized. When the timer counts down to zero, the relay de-energizes. Set the timer at parameter 'time' in the
1 Menu Level. See Table below.
st
'10' SOAK ON-Timer Upon power-up, the alarm relay is de-energized. When the PV = SV the alarm relay
energizes. When the timer counts down to zero the relay de-energizes. Set the timer at parameter 'time' in the
1 Menu Level. See Table below.
st
'11' SOAK OFF-Timer Upon power-up, the alarm relay energizes. When the PV = SV the alarm relay de-
energizes. When the timer counts down to zero the relay energizes. Set the timer at parameter 'time' in the 1
Menu Level. See Table below.
'A1Fu'
Setting ALARM RELAY MODE
8 EVENT ON-TIMER
9 EVENT OFF-TIMER
10 SOAK ON-TIMER
11 SOAK OFF-TIMER
EVENT and SOAK Timer Relay States
ON = Alarm Relay energized
rd
Menu Level parameter 'A1Fu' (Alarm Function). The
(400 – 10 = 390).
o
Relay Relay state when PV=SV
at Power-up (Timer Starts counting)
OFF OFF
ON ON
OFF ON
ON OFF
OFF = Alarm Relay de-energized
24 Model 48VTR - Version 5.0 – January 2006
st
Menu Level.
st
Relay after Timer
Counts Down
ON
OFF
OFF
ON