GE Mini Field Agent, User Manual

Page: 81 / 87

GFK-2993F 81
For public disclosure
6.2.5 Guidelines for Maximum Configured Variables
All variables read from the Server by a Machine Adapter are published. The OPC UA Machine Adapter supports OPC UA
Subscription functionality, which can be used to limit the variables published to those that have either changed or changed
more than a specified amount since the last subscription interval. Other protocols do not include this functionality; Machine
Adapters for these protocols will publish all variables configured to be read each interval.
Variables of type LREAL (OPC UA type Double) are supported for both OPC UA and Modbus TCP Machine Adapters; one
LREAL may be configured and published in the place of two 4-byte or smaller variables. This formula may be used to
calculate the effective number of 4-byte or smaller variables when also configuring and publishing LREAL variables:
(# of 4-Byte or smaller variables) + (# of LREAL variables * 2) = Effective Variable Count
When using multiple Subscriptions, the maximum number of configured variables and the maximum number of published
variables is cumulative across all Subscriptions on a given Field Agent. When using different PublishInterval settings for
different subscriptions, the fastest PublishInterval in use should be used to determine the maximum numbers of configured
and published variables.
6.2.5.1 Using the OPC UA Machine Adapter without Store and Forward
NOTE
Using the OPC UA Machine Adapter without Store and Forward is not currently supported on the EFA or VFA.
When Store and Forward is disabled, the OPC UA Machine Adapter limits for the Mini Field Agent platform are displayed in
the following table.
Supported Configurations for OPC UA Machine Adapter with Store and Forward Disabled on MFA
PublishInterval (ms)
Configured 4-Byte Variables Max Published
500-999
600
300
1000-1999
1,200
600
≥2000
1,200 1,200
Note For ICMFA000000-AAxx only, multiply the values in the above table by 0.83 to calculate the OPC UA Machine
Adapter limits when Store and Forward is disabled.
Note Some OPC UA Servers may negotiate a different interval at the time of the connection if the configured
PublishInterval does not match its available subscription intervals. It is recommended to confirm that the OPC UA Server to
which the Mini Field Agent is connected can serve data at the requested interval.
Note The minimum supported OPC UA Machine Adapter PublishInterval on the Mini Field Agent is 500ms when running
Predix Machine 17.1.2 or later.