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OMB-DAQ-TC-RACK User's Guide
Functional Details
15
Figure 7. Example of digital output/alarm controlling a relay
The alarm configurations are stored in non-volatile memory and loaded at power up.
Alarm settings are applied when changed and at power on. Temperatures are constantly converted on enabled
channels and processed for alarm conditions regardless of the communications connectivity.
Each available alarm mode and setting is explained below.
Alarm input modes
Set independent temperature thresholds T1 and T2
for each alarm.
Trigger alarm when input temperature ≥ T1; reset alarm when
input temperature < T2
Trigger alarm when input temperature ≤ T1; reset alarm when
input temperature > T2
Trigger alarm when input temperature is < T1 or > T2
Alarm error modes
Alarm on temperature reading only
Alarm on temperature reading, open thermocouple, or common-
mode voltage error
Alarm on open thermocouple or common-mode voltage out-of-
range error only
Alarm output modes
Alarm disabled; digital output line can be used for normal
operation
Alarm enabled; active low output (output line goes low when
alarm condition is met)
Alarm enabled; active high output (output line goes high when
alarm condition is met)
Alarm output may be latched and will not clear unless explicitly
cleared by the user
The OMB-DAQ-TC-RACK provides three alarm indicators – the
, the
front panel and, optionally, the user-configurable digital outputs associated with each channel.
Because the digital alarm outputs are user-configurable, they can be used to supply additional information
(visually, if the digital outputs are used to drive LEDs), such as the channel associated with the alarm condition
or differentiating between threshold and common mode voltage out-of-range alarms.
Pull-up configuration
By default, pull-up is enabled for all eight digital inputs and all 32 digital outputs. Slide switches on the rear of
the housing can disable pull-up for each digital input bit and digital output bit.
When pull-up is disabled for a digital bit, the bit is left floating.
LED indicators
The OMB-DAQ-TC-RACK has four LEDs that indicate the power, communication, alarm, and open TC status