Configuring a Rate of Change Maths Channel

From the left-hand side of the Maths screen, select Add Math .

If you are not already in Configuration lock, the Configuration lock screen displays:

Enter a reason if required and then select Confirm . The system configuration is now locked pending the submission of your update and the Configuration Locked icon displays on the status bar.

The Add channel screen displays, from Type, select Rate of Change from the available list and select Add :

From the left-hand side of the Maths screen, select the Rate of Change Maths channel required. The Math Configuration section displays on the right-hand side:

If you are not already in Configuration lock, the Configuration lock screen displays:

Enter a reason if required and then select Confirm . The system configuration is now locked pending the submission of your update and the Configuration Locked icon displays on the status bar.

Complete the configuration as required:

• Type - Defaults to Rate of Change.

• Descriptor - Defaults to Math <n> where n is the next number in sequence from the previous Maths channel. We recommend that you enter a meaningful name for the channel (maximum 40 characters), for example,“ROC” or “Gradient”.

  Note - This is not case sensitive, for example, 'AbC' is regarded as identical to 'abc '.
  Tip - When an External link icon displays next to a function’s Descriptor, it indicates that one or more of its parameters are mapped to a Modbus server register table. Select External link to display the Modbus register address, data type and related mapping details, which enables alignment with the exported Modbus register map. See Exporting a Modbus Address Map for details.

• Math Configuration - Select Expand if it does not expand automatically:

  • Input - Value to be calculated. Select a dynamic data source, for example, an I/O channel or Maths channel from the available list or enter a numeric constant, see Linking a Channel as an Input for details.

  • Time Unit - Select a time unit to derive the output (Seconds, Minutes, Hours, Days).

  • Filter Time - Time constant to configure the first-order filter applied to smooth the rate-of-change output and reduce noise sensitivity. Select a dynamic data source, for example, an I/O channel or Maths channel from the available list or enter a numeric constant, see Linking a Channel as an Input for details.

    Tip - When Filter Time is increased, the output becomes smoother and less sensitive to short spikes, but it also responds more slowly.

  For example, if the Input is a temperature signal and it rises from 20°C to 26°C in 3 minutes, then:

  with Time Unit = Minutes, the rate of change is 2°C/min

  with Time Unit = Seconds, the rate of change is about 0.033°C/s

From the left-hand side of the Maths screen, select the Rate of Change Maths channel required. The Chart and presentation settings section displays on the right-hand side:

If you are not already in Configuration lock, the Configuration lock screen displays:

Enter a reason if required and then select Confirm . The system configuration is now locked pending the submission of your update and the Configuration Locked icon displays on the status bar.

From Chart and presentation settings, select Expand if it does not expand automatically and complete as required:

• General Settings:

  

  • Units - Enter an engineering unit, for example, °C, psi or Volts, up to a maximum of six characters. For information on entering special characters, see How do I enter special characters?.

    Tip - The unit displays with the channel value on the Operator Panel.

  • Number Format - Select either:

    • Numeric - Displays values in decimal format, for example, 12345.6789 displays as 12,345.6789.

    • Scientific - Displays values in scientific notation, useful for very large or very small numbers. Numbers display as a coefficient multiplied by a power of 10, for example, 12345.6789 displays as 1.23456789E+4.

  • Decimal Places - Enter the value, or use the Plus or Minus to set the decimal place (0 to 6).

  • Color - Select a color from one of the 56 available colors:

    

• Scale & Zone Settings:

  

  To set the chart scale and zoning for this channel:

  • Scale Enable - Tick to enable scale configuration and specify the scale type and the number of divisions required:

    • Scale Type ( available only when Scale Enable is enabled) - Select one of the following options:

      • Logarithmic - Divisions are displayed using a logarithmic scale. This option is suitable for analyzing data spanning multiple orders of magnitude.

      • Linear - Divisions are displayed at equal intervals. This option is ideal for displaying uniformly distributed data:

        • Scale Division Major ( available only when Scale Type is Linear) - Enter a value, or use the Plus or Minus to set the major divisions to be included on the chart (valid range 1 to 20).

        • Scale Division Minor (available only when Scale Type is Linear) - Enter a value, or use the Plus or Minus to set the minor divisions to be included on the chart (valid range 1 to 20).

          Note - Scale divisions have no impact on a chart grid, they are only for scale. The grid on the chart is defined by the division settings on the group, see Configuring Groups Settings for details.

  • Scale maximum (Unit) - Enter a value, or use the Plus or Minus to set the upper limit of the scale's range.

  • Scale minimum (Unit) - Enter a value, or use the Plus or Minus to set the lower limit of the scale's range.

  • Zone maximum (%) - Enter a value, or use the Plus or Minus to set the percentage offset for the upper limit of the scale and trendline relative to the top of the chart (valid range 5 to 100).

  • Zone minimum (%) - Enter a value, or use the Plus or Minus to set the percentage offset for the lower limit of the scale and trendline relative to the bottom of the chart (valid range 0 to 95).

    Note - The minimum value must be less than the maximum value by 5 or more.
    Tip - The Zone settings offset a scale and its associated trendline relative to the chart grid. This is useful when displaying multiple trends with similar value ranges, which would otherwise overlap and become difficult to distinguish. For example, several digital trends switching between 0 and 1 can overlap, making them difficult to distinguish unless each is defined a different Zone.