History Ordinals and Points

The relationship between Emerson ROCPlus field devices and CygNet history data groups is defined by the use of RAM areas, segments, points, and ordinals. To some extent, this is also true of FMS data groups because they depend on native history data groups for their data.

Because the process of configuring a CygNet data group to "talk" to a field device begins at the field device, the following information first provides details about field device history points, then native history data groups, and finally EFM data groups.

For more information, see the following subsections below:

• Field Device RAM Areas, Segments, and Points
• Native History Data Group Ordinals, RAM Areas, Segments, and Points
• To Find History Segments and Points
• FMS History Data Group Ordinals, Segments, and Points
• To Add Segment and Point Numbers

In order for your Emerson ROCPlus EIE to collect historical information for a given field device, that device must be properly configured. See the appropriate manufacturer-provided documentation.

Field Device RAM Areas, Segments, and Points

For Emerson ROCPlus devices, a combination of history segments and points define where and how data is stored on and recovered from a field device. Segments define the rate of collection and the number of indexed records available. Points simply contain values.

The following list breaks down RAM areas, segments, and points by model and series number:

• Emerson ROCPlus Series 1 field devices use history segments (general and 1 - 10, which are often referenced as 0 - 10) and points (1 - 200) within those segments to access history.
• Emerson ROCPlus Series 2 field devices use history segments (general and 1 - 12, which are often referenced as 0 - 12) and points (1 - 200) within those segments to access history.

Native History Data Group Ordinals, RAM Areas, Segments, and Points

Ordinals

Each CygNet data group added to a remote device is identified by a number called an ordinal. The ordinal is specified on the Data Group Properties page.

For native history data groups, the ordinal derives from an associated history point on a field device. However, history point numbers alone are not always enough to locate and access a point's data. So CygNet history ordinals sometimes derive from a combination of values, as with Emerson ROCPlus devices. Emerson ROCPlus devices combine a segment number with a point number in order to create an ordinal.

RAM Areas, Segments, and Points

For Emerson ROCPlus devices, a combination of history segments and points define where and how data is stored on and recovered from a field device. Segments define the rate of collection and the number of indexed records available. Points simply contain values.

The following list breaks down RAM areas, segments, and points by model:

• Periodic history data groups on Emerson ROCPlus Series 1 remote devices require you to specify a segment (1 - 10) and point (1 - 200). They then automatically create an ordinal with a range of 0 - 2199.
• Periodic history data groups on Emerson ROCPlus Series 2 remote devices require you to specify a segment (1 - 12) and point (1 - 200). They then automatically create an ordinal with a range of 0 - 2599.

To Find History Segments and Points

For an Emerson ROCPlus EIE, find a segment by polling the correct Station # on a "Station Parameters" data group; the segment appears in the History Segment field.

Find points by polling the correct Segment # on a "History Point Configuration" data group; the points appear in the Pt# column.

FMS History Data Group Ordinals, Segments, and Points

Ordinals

FMS history data groups also use ordinals. However, these ordinals are associated with a meter, not a history point. When you specify a Meter# in an FMS history Data Group Properties dialog box, that number displays in the Ordinal column under the Data Group page.

Segments and Points

To Add Segment and Point Numbers

For Emerson ROCPlus devices, the "FMS History" data groups must be configured automatically with Segment # and manually with History Point numbers. After a Segment # is assigned to an FMS history data group, specify the history points needed to map process variables between CygNet and a connected field device. The History Point value is a point number within a segment.

Example

For an Emerson ROCPlus remote device, imagine differential pressure is collected on a field device in segment 11, point 2. A "Periodic History" data group is created to retrieve this data. Specifying segment 11, point 2 in the Data Group Properties dialog box automatically generates an ordinal of 414, which is computed by the CygNet Explorer remote device editor. To collect differential pressure as part of meter 1 FMS history data, the differential pressure process variable for FMS history data group ordinal (meter) 1 must specify the history point as 2.

The following procedure explains how to find and add segment and point numbers to an Emerson ROCPlus remote device that uses FMS.

1. Open CygNet Explorer.
2. Click Device Definition Service (DDS) in your service hierarchy.
3. Locate the remote device you want to alter and double-click it to open its remote device editor.
4. Click the Data Group page.
5. Add, configure, and poll an FMS configuration data group for the meter from which you want to collect history.
6. Add and configure an FMS history data group. Make sure that the history data group's Meter # is the same as the FMS configuration data group added in step 5. See steps 7 and 8 for details.
7. Close and reopen the FMS history data group from step 6 to populate its Segment # field with the correct segment.
8. In the FMS history data group from step 6, assign history points to process variables. Exactly what each number represents depends on your field device set up. FMS history data groups require no predefined history points.
   1. Locate the process variable for which you want to assign a history point, and click in the corresponding History Point field to display a Browse button.
   2. Click the Browse button to open the Browse History Points dialog box.
   3. Select the correct history point from the list of available items.

9. When you are done assigning history points to process variables, click OK.
10. Click Apply to save the FMS history data group configuration.
11. You may now poll the FMS history data group from step 6.