Configure Integer and Cardinal Point Scaling

Use the fields within the Scaling section of the <Point Type> tab to configure an SNMP Integer or Cardinal Point’s scaling. The SNMP driver applies the scaling to each integer or cardinal value that it retrieves from an SNMP agent, before passing the resultant value to the ClearSCADA database. The driver applies the scaling in reverse whenever the Set Value pick action is used.

• Multiplier—Use to specify the amount by which the SNMP driver is to multiply each value that it retrieves from the SNMP agent. The driver then applies the relevant Offset before passing the resultant value to ClearSCADA.
• Leave at the default of 1 if the driver is not required to perform such a multiplication task.
• Offset—Use to specify the amount that the SNMP driver is to add or subtract from each value, once the Multiplier has been applied.

  Leave at the default of 0 is no addition or subtraction is required.

  Example 1:

  An SNMP Integer point’s configuration includes this Scaling:

  Multiplier: 0.1
  Offset: 5

  The SNMP driver applies the scaling to each integer value that it retrieves from the SNMP agent with which the point is associated.

  In this particular case, the driver multiplies the retrieved value by 0.1, then adds 5 to that value, before passing the resultant value to the ClearSCADA database.

  So if the driver retrieves an integer value of 45, for example, it will pass a value of 9.5 to ClearSCADA (as (45 x 0.1) + 5 = 9.5).

  Example 2:

  Another SNMP Integer point has its Set Value Enabled check box selected in the Poll/Link Status section of the Point Form. The SNMP driver has read/write access to the SNMP agent with which the point is associated, and write access to the community specified in the point’s Community Name field.

  The point’s configuration includes this Scaling:

  Multiplier: 0.1
  Offset: 5

  An operator uses the Set Value pick action to set the point value to 20.

  The ClearSCADA server passes the value to the SNMP driver, which applies the point’s scaling in reverse (deducting the Offset and dividing by the Multiplier).

  This results in the driver sending a command to the SNMP agent to set its value to 150 (as (20 - 5) / 0.1 = 150).