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Configuring I/O
7.8
DOUT Type options and examples
For all settings of DOUT Type except Latched, the DOUT Type parameter controls the relationship
between the discrete output's On period and Off period.
The following sections provide information on how the duration of the cycle, On period, and Off
period are determined, and examples of DO configuration. In these discussions, one On period plus
one Off period equals one cycle.
7.8.1
Accuracy of Time Duration and TDO Toggle
The DO state calculation is updated at one-second intervals. The calculated On period is then rounded
to the nearest second to produce the actual On period, for example:
•
Calculated On period = 4.4 seconds; actual On period = 4 seconds
•
Calculated On period = 4.5 seconds; actual On period = 5 seconds
7.8.2
Durations
DOUT Type = Toggle
•
Cycle = Time On parameter setting x 2
•
On period = Off period = Time On parameter setting
DOUT Type = Time Duration
•
Cycle = Cycle Time setting
•
On period = Calculated from the current EU value of the assigned process variable
•
Minimum Off period = Cycle Time minus On period
DOUT Type = TDO Toggle
•
Cycle = Cycle Time setting
•
On period = Calculated from the current EU value of the assigned process variable
•
Off period = Cycle Time minus On period
7.8.3
Examples
A discrete output is used to emulate a field instrument that measures flow. The DO is configured as
follows:
•
DOUT Type = Time duration
•
Cycle Time = 12
•
0% Count = 3
•
100% Count = 12
•
Low Reading EU = 0
•
High Reading EU = 1000
•
Units = MCF (million cubic feet per day)
78
®
Micro Motion
Model 3711 Gas Flow Computers
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Troubleshooting
