Lake Shore 370, Руководство пользователя

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Lake Shore Model 370 AC Resistance Bridge User’s Manual
Linear Equation (Continued)
A setpoint setting screen appears in the sequence if temperature control is disabled because the
Setpoint
key is locked out.
Linear Setup
Channel 1
Enter A Value For
Setpoint: 100.00 mK
Use the data entry keys to enter a setpoint value. Enter the numeric value first. Press
Enter
to accept the new value and
advance to the units multiplier. Use the
s
or
t
key to select a units multiplier of m, blank, k, or M. Press
Enter
to
accept the new selection and return to the normal display. Press
Escape
to restart the setting sequence and enter a new
value. Press
Escape
again to cancel the sequence and return to the normal display.
4.14 ALARMS
The Model 370 can compare reading data from each channel to a high and low alarm setpoint. Alarm setpoints and most
other alarm parameters can be set independently for each channel. If the Model 3716 Scanner is installed, the alarm
operates for the active scan channel only. The alarm feature uses filtered reading data when the filter is enabled.
When any alarm is enabled the Alarm annunciator will be shown on the top line of the display. The annunciator remains
steady if neither alarm is in the active alarm state. It blinks when either alarm is active. The alarming channel does not
have to be displayed for the alarm annunciator to indicate status. If a Model 3716 Scanner is installed, the alarm
annunciator follows the active scan channel to indicate the alarm status of that channel. The instrument has an audible
alarm beeper that can be programmed to sound is any of the alarms are active. The relays described in Paragraph 4.15
can also be programmed to follow the alarm feature.
The alarm feature has two modes of operation, latching and non-latching. The operation of these modes is described
below.
Latching Operation:
During latching operation, if the reading value is ever greater than the high alarm setpoint, the
high alarm for that channel is latched in as an active state. Similarly, if the reading value is ever lower than the low
alarm setpoint, the low alarm for that channel is latched in. The alarm remains active until the alarm condition has
been cleared
and
the alarm feature is reset. This mode is often used to detect faults in a system or experiment that
require operator intervention. The alarm remains visible to the operator for diagnostics even if the alarm condition no
longer exists.
Non-latching Operation:
During non-latching operation, the high alarm remains active only as long as the reading
value is greater than the high alarm setpoint. Similarly, the low alarm remains active only as long as the reading value
is lower than the low alarm setpoint. No action is required from the operator to reset the alarm state after the alarm
condition is cleared. The deadband parameter is available to prevent the alarm from chattering (turning on and off
repeatedly) when the reading value is very near the setpoint. This mode provides a simple form of control that is often
actuated through a relay. An example of non-latching operation is shown below.
High Alarm Setpoint
Low Alarm Setpoint
Deadband = 5 K
100 K
50 K
95 K
55 K
Alarm Latching Off
Temperature Reading
High Alarm Activated
High Alarm Deactivated
Low Alarm Activated
Low Alarm Deactivated
Deadband.eps
Figure 4-2. Deadband Example
4-26 Operation