Digital Outputs In Manual Mode; Digital Input Modes; Input Alarms; Enabling An Input Alarm - Lakeshore 340 User Manual

7.2.4

Digital Outputs in Manual Mode

In manual mode, the digital outputs are controlled directly by the user. The digital output signals can be set to
any combination of high (logic 1) or low (logic 0). Digital output can only be set using the 0 and 1 keys. For
example: a setting of 00011 causes digital outputs 1 and 2 to be high (logic 1) and digital outputs 3, 4, and 5
to be low (logic 0).
To manually set a digital output, set the digital output mode to manual as described in Paragraph 7.2.1. Press
the Options key and the Digital I/O screen appears. Press the Next Setting key until the Reading line is
highlighted. Use the number keys, 0 and 1, to enter a setting that corresponds to the digital output numbers
shown below the setting on the display. Press the Save Screen key to store the changes. The default value is
00000.
7.2.5

Digital Input Modes

The digital input signals are always read by the Model 340. Their status is always available from the front
panel or over computer interface. The only defined application of the digital inputs is during external scanner
operation (refer to Paragraph 5.4). If external scanner operation is not being used, the inputs are considered
to be in manual mode.
7.3

INPUT ALARMS

Each input of the Model 340 has a high and low alarm setting. Input reading data in temperature units, sensor
units, or from linear equation can be compared to the alarm values. If a reading is higher than the high alarm
setting the high alarm is active for the input. If a reading is lower than the low alarm setting the low alarm is
active for the input. The alarm feature can be enabled or disabled for each individual input.
Active alarms are indicated on the display with an annunciator. The Alarm annunciator indicates that there is
an input alarm enabled. An Alarming annunciator indicates that an enabled alarm is active. An audible
beeper can also sound to indicate an alarm is active. The audible beeper can be turned off for all alarms. One
or more sets of high and low alarms can be directed to the high and low alarm relays. Parameters on the
RELAY & BEEPER SETUP screen must be changed for the alarm relays and beeper to be active, as
described in Paragraph 7.4.
The alarms can operate in latching or non-latching mode. In non-latching mode, an active alarm becomes
inactive when the alarm condition is corrected. This mode is often used in control applications where an alarm
event is triggered inside the normal operating range of the input sensor. In latching mode an active alarm is
held active even after the alarm condition is corrected. This mode is most often used as a safety feature to
discontinue an external activity if the input sensor is outside of a safe operating range. The Alarm Reset key
is used to reset a latched alarm.
7.3.1

Enabling an Input Alarm

To enable an input alarm, press the Alarm Setup key. The ALARM SETTINGS screen appears with the input
letter in the top left hand corner. Use the s or t key to select an input. Press the Enter or Next Setting key
to show the alarm parameters for that input. Press the Next Setting key until the Enable field is highlighted.
Use the s or t key to turn the alarm on or off for that input. Use the Next Setting key to make more
changes, or press the Save Screen key to store the changes. The default setting is Enable Off.
7-4
Lake Shore Model 340 Temperature Controller User's Manual
Analog, Digital, Alarm & Relay Operation