Table Of Contents

Streams of Data

Last Modified: October 16, 2020

NI monitoring devices, such as Condition Monitoring Systems (CMS) and Motor Current Signature Analysis (MCSA) systems, are designed to detect when a piece of equipment enters a particular state of behavior, and then collect and group a series of data files until the equipment reaches a steady state. For example, a device might detect when a turbine begins a run-up when the speed measured by a tachometer increases to above 200 RPM, and then enter an operating state in which it collects and groups files. When devices group files in this way, the resulting files are referred to as a stream. The Data Viewer page provides several features for displaying data that has been acquired as part of a stream.

Introduction to Streams

A stream is a single entity that combines many measurements from one device for the purpose of visualizing the data as a group. This is useful because by interacting with a single stream, you can quickly view all data the device acquired when the equipment was experiencing the behavior of interest. In the case of run-ups and coast-downs, where speed measurements cause a data group to enter a stream-enabled operating state, a stream contains the trend of speed measurements throughout the run-up or coast-down, as well as data from each sensor in the data group.

How Streams Work

The following steps describe the actions that occur during a stream-enabled operating state to produce a stream:

  1. A device detects when a particular expression evaluates true and starts collecting files. For example, a device might detect a run-up when the speed increases to above 200 RPM, and then start a cycle of collecting ten seconds of data, waiting for fifteen seconds, and then repeating.
    spd-note-note
    Note  

    Users configure stream settings, such as the expression that triggers stream acquisitions, on a per-equipment basis on the Properties tab of the Asset Configuration page.

  2. NI InsightCM Server receives data from the device and makes the data available for viewing in on the Data Viewer page.
    spd-note-note
    Note  

    On the Data Viewer page, you can subscribe to the stream to update viewers with live data. Watching a Live Stream

  3. The device detects the stop condition that indicates the equipment reached a steady state, and then stops performing stream acquisitions.
  4. On the Data Viewer page, you can load the stream of data that the server created.

The following illustration shows the role of each component.

Run-Up Example

The following workspace shows the Data Viewer page with a run-up stream loaded. Notice the following characteristics:

  • The workspace is in continuous-data mode.
  • The Trend viewer contains a single trend of speed values from the tachometer whose measurements indicate a run-up and trigger stream acquisitions.
  • The Trend viewer time axis is restricted to the duration of the run-up. In other words, you cannot adjust the time range to show other historical measurements that occurred before or after the run-up.
  • Other viewers contain measurements from several different sensors.
  • If you place a cursor in the Trend viewer and move it with the arrow keys, the data in the other viewers will update to match the timestamp of the Trend viewer.

Behavior when Devices Monitor Multiple Pieces of Equipment or Multiple Devices Monitor the Same Equipment

Streams consist of all the data that sensors on a specific data group acquire. A data group is a set of channels mapped to sensors that monitor the same piece of equipment. Data groups are useful in situations where a single device connects to sensors on multiple pieces of equipment whose data you want to acquire according to different parameters.

Multiple devices cannot share a data group. This means that if two devices monitor one piece of equipment, only data acquired by the one data group that experiences the enter condition is part of the stream.

If a device monitors two pieces of equipment, each with unique operating behaviors, ensure the equipment belong to separate data groups. Otherwise, if the data group experiences an enter condition that is relevant for only one piece of equipment, the device includes data from the second piece of equipment as part of the stream.

Streams versus Periodic Acquisitions

Data streams are similar to periodic acquisitions in the following ways.

  • The InsightCM Server stores both types of data.
  • The Trend viewer displays values from both types of acquisitions.

Streams differ from periodic acquisitions in the following ways:

  • Users can configure a device to continuously collect files at intervals of only a few minutes or delta EUs when it enters a stream-enabled operating state. However, periodic acquisitions might occur much less frequently, such as only when a time interval elapses or a delta EU or alarm condition evaluates true.
  • Separate aging rules apply to stream and periodic data files.

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