MA1044 MAQ20-RTD31/-RTD41 Hardware User Manual
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15.0 Alarm Functions
The powerful alarm functions in the MAQ20 Data Acquisition System provide essential monitoring
and warnings to ensure optimum process flow and fail-safe applications. Alarms have the following
parameters which can be configured:
Alarm Enable
Enables the Alarm on a given channel provided that the Alarm Configuration Register has a valid
configuration. Set the bit corresponding to the given channel to a 1 to enable the alarm. If the Alarm
Configuration register for the given channel does not have a valid value, the write will be ignored
and the Alarm Enable bit will remain 0. Write a 0 to the bit corresponding to the given channel to
disable the alarm and clear any alarms that have tripped.
Alarm Configuration
Selects Tracking or Latching alarms for a given channel and selects which limits trip the alarm -
High, Low, High-High or Low-Low. There is a register for each channel. The value written to this
register is the sum of the codes for the Alarm Type and Alarm Limits. See the
section for the specific codes. If an invalid value is written to this register, the value will be
ignored and the last valid value that the register contained will be kept. If a 0 is written to the register,
the Alarm Enable register for the channel will be set to 0 and alarms that the channel has tripped
will be cleared.
Tracking alarms follow the value of the input signal and reset automatically when the signal comes
back into the valid range specified by the limit and deadband. Latching alarms trip when the signal
exceeds the alarm condition and remain set until reset by the user.
High Limit
Sets the value for the High limit in counts. Alarm status is stored in a register.
Low Limit
Sets the value for the Low limit in counts. Alarm status is stored in a register.
High Low Deadband
Used for the High and/or Low limits to prevent false tripping or alarm chatter for noisy signals.
Deadband is the region less than the High limit or greater than the Low limit, measured in counts,
which the signal must traverse through before the alarm is reset after being tripped.
High-High Limit
Sets the value for the High-High limit in counts. Alarm status is stored in a register.
Low-Low Limit
Sets the value for the Low-Low limit in counts. Alarm status is stored in a register.
High-High Low-Low Deadband
Used for the High-High and/or Low-Low limits to prevent false tripping or alarm chatter for noisy
signals. Deadband is the region less than the High-High limit or greater than the Low-Low limit,
measured in counts, which the signal must traverse through before the alarm is reset after being
tripped.
See Figure 11 below for graphical representations of alarm parameters and functionality.