Sampling Modes

Many different sampling and calculation modes can be used on retrieval of data that has already been collected in the archive. Available sampling modes in Historian include:

These topics explain some of these retrieval concepts. Each sampling mode (except calculated) is described with details and examples, including how sample attributes are determined. Each sample returned by Historian during data retrieval has the following properties:

• Timestamp — time stamp of the collected sample or an interval time stamp
• Value — The collected value or sampled value
• Quality — Each sample in Current Value and Raw retrieval has a quality of "good" or "bad". Interpolated and Lab Retrieval express quality as a "per cent good".

Current value sampling is the simplest retrieval mode. Raw data retrieval is the second simplest method of retrieval. Intervals and interpolation concepts are common to Interpolation and Lab sampling. Interpolation and lab sampling are presented together so that they can be contrasted for values and qualities returned from the same set of collected data.

Example Data: Each topic contains all necessary data for executing each example in the form of a CSV file that can be imported by the Historian File collector. You will have to copy and paste the appropriate data into a separate file with a CSV file name extension. Delete all archives before importing the data. You will not be able to import the data unless you adjust the active hours setting; this is true any time you import old data with the File collector. For details, see Historian documentation.