### Time Constant The information below provides a FULL description of this microblock and all of its properties. What information you see and what you can do with it depends on your license and the application you are in, and in some cases, a controller's driver version.
Microblock family | Sys In microblocks
Icon and symbol |
What it does | This microblock specifies a time value to be sent to another microblock in the control program. Time Constants do not appear on the Properties page and should be used instead of Time Parameter microblocks when the value of the microblock will not change.
#### Properties TIPS Alt+click any value in the WebCTRL® or Field Assistant interface to view property details, including its editing privilege and expression (location path) for use on graphics. You can right-click some properties in the EIKON® Property Editor and select Make editable or Make read-only to determine that property's functionality in your system.
Reference Name RefName | Use the default reference name unless you want a more descriptive name for graphics or network links. Limitations: lower case only limited to 40 characters cannot begin with a number must be unique within a control program
Present Value | The value that the microblock uses on the control program output wire. For constant microblocks, this value can only be changed in the EIKON® application. For parameter microblocks, this value can be changed in the WebCTRL® or Field Assistant system or in the EIKON® application.