Vaisala DMT152 - Manual (Page 41)

Chapter 5 ________________________________________________________ Serial Line Operation
VAISALA ________________________________________________________________________ 39
Limit Alarm
The limit alarm is activated when the measured quantity goes below the
low limit or above the high limit. The alarm can be specified during
ordering for a specified parameter, or configured on the serial line using
the ALARM command.
When ordering a limit alarm, the alarm levels are set as follows:
- For current output, an active alarm is indicated by the current being
at the maximum of the scale (20 mA).
- For voltage output, an active alarm is indicated by the voltage being
at the maximum of the selected scale. For example, if the voltage
output scale is 0 … 5 V, an output of 5 V indicates the alarm is active.
Using the ALARM command, you can also set a hysteresis value to
prevent the repeated triggering of the alarm when the measurement
fluctuates around a limit value.
ALARM<cr>
The following example shows that a high limit alarm has been enabled
for channel 1. If the measured value rises above the -40.00 °C T
d
limit,
analog channel 1 is set to 5 V (Limit Hi = -40.00, Level Hi = 5.00). The
malfunction alarm (aerr) is disabled for both channels.
alarm ?
Channel 1:
Low Limit : OFF
High Limit : ON
Aerr : OFF
Quantity : Tdf
Limit Lo : 0.00
Limit Hi : -40.00
Hysteresis : 0.00
Level Lo : 0.00
Level Hi : 5.00
Channel 2:
Low Limit : OFF
High Limit : OFF
Aerr : OFF
Quantity : ppm
Limit Lo : 0.00
Limit Hi : 0.00
Hysteresis : 0.00
Level Lo : 0.00
Level Hi : 0.00
NOTE Avoid enabling more than one alarm type for a channel.