Quality

Quality of data value as string

Description

Quality indicates the quality of the daitem object's Value property as a string. You can use the Quality property to determine if a value is useful or not.

The Quality string is made up of a major quality string, a substatus string, and an optional limit status string, arranged in the format 'Major: Substatus: Limit status'. The limit status part is omitted if the value is not limited. The major quality can be one of the following values:

Value

Description

Bad

The value is not useful for reasons indicated by the Substatus.

Good

The value is of good quality.

Uncertain

The quality of the value is uncertain for reasons indicated by the Substatus.

For a list of substatus and limit status values and their interpretations, consult OPC Quality Strings.

Quality is updated when you perform a read operation using read or readasync, or when a subscription callback occurs. Quality is also returned during a synchronous read operation.

Characteristics

Access

Read-only

Applies to

daitem

Data type

string

Values

The default value is 'Bad: Out of Service'.

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