Analog value filtering (wwFilter)

You can use the following analog filters for all retrieval modes:

• Statistical removal of outliers

• Analog to discrete conversion

• Zero around a base value

These filters are applied in a query to retrieve data from the History table, WideHistory table, or StateWideHistory table. These filter only apply to analog tags. All other types of tags, including analog summary tags, are not supported.

You need to specify a filter name in the virtual column wwFilter, with or without an override, to the set of parameters that are defined for the specified filter. The filters are specified as C-like functions: parentheses are always required, even when you choose not to override the default parameters by passing no parameters.

The default value for the wwFilter column is ‘NoFilter’. If the query does not specify the wwFilter element at all, or if its default value is not overridden, then no filter is applied.

When you use the analog filters in a query that uses wwQualityRule, wwQualityRule is applied first and wwFilter is applied later. You can only use one filter per query.