**The Magic of Math Constants**

Many configurations will use math constants for their most basic purpose, to store a constant number used elsewhere in the configuration. However, there are multiple other uses of math constants to help you accomplish what you need.

Math constants’ ability to switch between alternate values, in addition to their uses within Controller Channels, Calibrations, and Condition Manager, can save you time and make your life easier!

**Alternate Values**

Math constants can be assigned up to two input expressions that will change the value of the math constant. When the configured ‘Secondary Input Expression’ is true, the value of the math constant will change to whatever is configured in the ‘Secondary Value’ field. The same pertains to the ‘Tertiary Input Expression’ and ‘Tertiary Value’ fields. If both the secondary and tertiary input expressions are true, the secondary input expressions will take precedent. Should neither input expression be true or if neither expression is configured, the math constant will remain equal to the ‘Primary Value’.**Controller Channels, Calibrations, and Condition Manager**

In addition to configuring alternate values for a math constant, constants can also be written by other elements of the configuration. Channels can be set to write a particular interval to a math constant. In addition, calibrations are able to write the results of a calibration or even the expected value of a calibration to a math constant. Even Condition Manager is able to write to a math constant when run within ProcessNow. Writing a constant with a Condition Manager script even allows you to send something like a 30-day average calculated by the server down to the logger.**Precautions**

When using math constants, the value of the constant is not stored like the value of a channel. If a historical record of a constant is required, the math constant should be associated with a parameter. In addition, if a parameter using a math constant is not associated with a channel, you must specify within StackStudio which controller it should look at. This means that you are unable to use multiple math constants from different controllers within the same equation.

##### To better understand how your system uses math constants, contact the ESC support team.

512-250-7901 • support@envirosys.com

If you think you can use any of these features of math constants in your system, contact ESC Sales for Engineering support.

512-250-7902 • sales@envirosys.com

Clint Anderson, System Implementation Engineer, ESC Published: 12/14/2016 5:10:39 PM