Instrument WriteValue Method is used to change the value of the ProcessVariable in the MDISInstrumentOutObjectType. The Instrument WriteValue Method operation applies to the object in the subsea system. Some systems will be able to report any errors immediately others will only be able to report that the operation was not refused. Clients are expected to monitor the ProcessVariable and ensure that the operation completed successfully. If an error occurs after the Method has returned, a Fault flag shall be set and an appropriate FaultCode will be returned. The Fault (and FaultCode) will reset on the next successful Instrument WriteValue Method invocation.

Method Declaration

WriteValue (

[in] Value Float

);

Table 18 – Instrument WriteValue Method parameters

Argument	Description
Value	Float value Variable, that indicates the target state of the Variable

Method result codes are defined as part of the Call Service (see OPC UA Services Part 4 – Services specification). They are described in Table 94 for ease of reference.

Comments

The WriteValue Method will change the value of the ProcessVariable Variable. The Method will report if any error occurs while writing the value of the Object. Table 19 specifies the AddressSpace representation for the WriteInstrumentValueMethod.

Table 19 – Instrument WriteValue Method AddressSpace Definition

Attribute	Value
BrowseName	Value
References	Node Class	BrowseName	DataType	TypeDefinition	Modelling Rule
HasProperty	Variable	InputArguments	Argument[]	PropertyType	Mandatory