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Reference Manual
00809-0100-4052, Rev AA
Section 4: DeltaV Ready
April 2015
21DeltaV
™
Ready
Section 4 DeltaV
™
Ready
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 21
Latency considerations in control logic design and operation . . . . . . . . . . . . . . . . . . . . . page 21
Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 21
Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 22
4.1 Overview
Native integration with DeltaV enables the Smart Wireless Gateway to be auto-sensed and easily
commissioned for seamless integration with all DeltaV applications: Explorer, Diagnostics, and
Control Studio. WirelessHART
®
devices can be easily added to the wireless field network and
then reconciled through DeltaV Explorer and assigned to analog channels through drag and
drop assignment.
4.2 Latency considerations in control logic design and
operation
Since the DeltaV wireless I/O scanner software requests updates for 1/5 of the devices each
second, DeltaV receives updates on a particular field device once every 5 seconds. That is not
necessarily synchronized with the update rate of the field device. Also, there is some latency
between when the field device takes a process sample and when it is permitted to pass its value
onto the wireless network. Status update responses can also increase latency in some instances.
So for example, if a device updates once every 8 seconds, and wireless network latency is 2
seconds, the amount of time that could pass between when an event occurred in the field and
before it is available to the DeltaV I/O bus is between zero and 15 (8+2+5) seconds. The update
period of the DeltaV control module should be added to that total to determine the range of
latencies before an event in the field can be acted upon by the control system.
Operators should be made aware that the update rate of wireless measurements on operator
screens are somewhat slower than those from wired devices. For example, if the operator
initiates a valve movement, it can be 5-15 seconds before confirming feedback appears on the
operator screen. Any control logic designed along the same principles should also take the
update rates and latencies into account as well.
4.3 Requirements
DeltaV
Version 10.3 or newer.
Smart Wireless Gateway
DeltaV Ready option