Manual

24 Watlow Series 935A User’s Manual
Configuration Menu
[``In]
Input Type
[`C_F]
Celsius/Fahrenheit
[``rL]
Input Range Low
[``rh]
Input Range High
[`Ot1]
Output 1 Function
[`Ot2]
Output 2 Function
[dISP]
Display Default
[ALtY] ✓
Alarm Type
[AhYS] ✓
Alarm Hysteresis
[`LAt] ✓
Alarm Latch
[`SIL] ✓
Alarm Silencing
[FAIL]
Failure Mode
Operations
Menu
[`Aut]
Auto-tune
[`ALO] ✓
Alarm Range Low
[`AhI] ✓
Alarm Range High
[`Pid]
PID
[CnFG]
Configuration
Learning Alarms
Alarms signal an excursion from normal operating conditions. In general, audible alarms or lights
connected to alarm outputs will signal a problem. In the 935A the front panel LED “1” or “2” indicates an
alarm with [``hI] or [``LO] flashing on the main display.
• Process alarms use absolute high and low values to trigger an alarm. Use this alarm type if your
process may be subject to temperatures that it must not exceed. Use [`AhI] and [`ALO] to set
alarm points at or near these values. See Table 10: [ALtY], next page.
• Deviation alarms are triggered by a deviation from the set point. The alarm high value [`AhI] is
the deviation above set point, and the low value [`ALO] is the deviation below set point. Whenever
the set point is adjusted, the alarm settings are relative to that value. Deviation alarms use the cur-
rently controlling set point, whether primary, remote, idle, or 90% of primary, during auto-tuning. See
Table 10: [ALtY], next page.
• Normally Open, [dEno] or [Prno], Alarms energize the alarm output when an alarm condition
occurs, and de-energize it when cleared. Use this type to activate external devices such as audible
alarms or lights. See Table 10: [ALtY], next page.
• Normally Closed, [dEnc] or [Prnc], Alarms de-energize the alarm output when an alarm condi-
tion occurs, and energize it when the alarm is cleared. Use this type as a “deadman” switch where
system continuity is required for operation. See Table 10: [ALtY], next page.
For example, by running the control output through the alarm output, you can set a normally
closed process alarm to disable the process when the process exceeds the alarm set point.
The alarm output will be off when power is off.
• Alarm Hysteresis sets a point the process must pass on a return (from an alarm condition excur-
sion) to the [`ALO] and [`AhI] points before the alarm can clear. This prevents the alarm output
from “chattering” if the process is hovering around the alarm set point. See Table 10: [AhYS], next
page.
• Latching Alarms require the operator to clear them with a ß press after the process returns to a
safe, or non-alarm condition. Non-latching alarms self-clear. See Table 11: [`LAt], p. 27.
• Silenced Alarms provide a means to clear the alarm output with a ß press even if the alarm
condition still exists. The flashing [``hI] or [``LO] message will persist until the alarm condition
ceases. See Table 11: [`SIL], p. 27. If [`SIL] = [`YES], alarms are disabled (no message or
output) on startup until the safe area is reached.
• Alarm High and Low Points, [`AhI] and [`ALO], in the Operations menu determine where
alarms will trigger. Alarm hysteresis [AhYS] determines where an alarm condition clears. See Table
11, page 27.
• To Clear an Alarm that is latched or “silence-able’ requires the operator to press the ß key after
the process returns to a safe, or non-alarm condition. Non-latching alarms self-clear. See Table 11:
[`LAt] and [`SIL], p. 27.
Table 10 (p. 25) and Table 11 (p. 27) illustrate the Series 935A alarm features.