Brooks Instrument MT3809E - Manual (Page 48)

3-8
Section 3 Operation
Models MT 3809 and 3819
Installation and Operation Manual
X-VA-MT3809-3819-eng
Part Number: 541B049AHG
September, 2008
Transmitter Analog Output: Analog Output HiRange, Analog Output
LoRange
d. Optional Programmable Alarm and Pulse Output Parameters and
Features
Alarm Contact Output: HiLimit, LoLimit
One or two digital outputs are available for a alarm signals. Contact output
polarity is configurable as Normally Open (N.O.) or Normally Closed (N.C.).
The alarms may be set at the minimum and maximum flow rate or at any
other preferred high and low limits. The units of measure of the alarm limits
is the same units of measure as the process variable itself.
Computations: Totalization
Totalizers are available in both Resettable and Inventory options.
Resettable totalization is used for batching while inventory totalization
measures the total volume over time. Units of measure are set
independently for each of these options.
Pulse Output: Pulse Out Scaler, Pulse Out Width
The SMM has a pulse output channel that indicates flow rate as a variable
frequency and therefore can pass information to many types of external
equipment such as batch controllers, automation systems or provers. The
output pulse width default is 1 millisec but may be user-configured since
certain external receiving equipment cannot keep up with high incoming
frequency.
Low Flow Cutoff Warning for Pulse Output and Totalization
The low flow cutoff parameter can be programmed to signal when the flow
level is below which the process is intended. Below this level, the totalizer
will assume that the flow rate is actually zero and that no data should be
accumulated by the totalizers.
Pulse Output Overrun Alarm
If a larger than acceptable output pulse width is configured, totalizer pulses
may be delayed or queued. No loss of pulses will occur. The totalizer
output pulses will to be sent until the queue is empty. Under these
circumstances, an alarm message will be sent to the control station.
However, the alarm can be disabled if not required.
Optional Alarm Configurations— Enable, Destination, Alarm Type
(Latching)
Three additional parameters may be programmed for process and
diagnostic alarms to control functionality — enable, destination, and alarm
type (latching). ‘Enable’ allows alarms to be enabled and disabled
depending on use of the alarm. For example, if output pulses are being
used it may be normal practice to delay (e.g. queue up) output pulses
because of a slow receiving end-device that requires a wide pulse-width.
The ‘enable’ parameter allows the user to disable the pulse output overrun
alarm and not send an alarm when in fact pulse outputs are delayed by
choice. Some critical diagnostic alarms, such as database initialization, can