# How to use Equation in TRNSYS

Simulation Studio provides a useful component called Equation. It can be used to process expressions that are not included in the standard components, define constants, and determine conditions.

In this article, using WBGT as an example, wet-bulb temperature and globe temperature are defined as Input, and WBGT equation as Output.

## How to use Equation

### Adding a New Equation

The first step is to insert a new Equation. Unlike the standard component, it is inserted by menu operation.

From the Simulation Studio menu, select [Assembly]-[Insert New Equation] to insert a new Equation.

Double-click on the inserted new Equation (the calculator icon) to open the Equation window. In this window, you can add or delete Inputs and Outputs, and add expressions.

### Adding an Input

Add a new Input and enter a name for it.

- Click on the document icon next to “Show input in Macro” and add a new Input.
- Enter a name for the added Input.

### Adding an Output and Entering the equation

Add an Output and enter the equation for the output.

- Click on the document icon to the right of “Intermediates & Outputs” and add a new Output.
- Enter a name for the added Output.

Next, enter the equation for the Output you have added.

- Select the Output you have added.
- Click on the magnifying glass button.

Then you will be able to enter the equation for the selected Output in the box in the middle of the window. Enter the equation here.

In the equation, you can use the Input item and function (bottom left of the screen).

The Equation thus added can be used in the same ways as the standard components, in combination with other components.

See the following article for an example of how it is actually used to calculate WBGT.

## Tips

### Functions

You can use the buttons at the bottom left of the screen to enter functions and operators.

For more information on functions, please refer to “6.3.9.1. Available mathematical functions” in the documentation.

### Edit all equations at once

Click on the “Edit all equations” button to open the input window. On this window, you can enter and edit multiple equations for Output.

## Examples

Here are a couple of links to some examples of Equation.

## Test Environment

It has been confirmed that the software works in the following environments.

Windows10 Pro(64bit, 20H2)

TRNSYS18.02.0002(64bit)