Script to find if a SQL Server Instance Exist

Kindly provide a good script to check if a sql server instance does exist. If not need to throw a good alert. I'm trying using the below script, but taking long time to execute. Any better way to write it, plz suggest $instance = "domain\INST4" $serverObject = New-Object Microsoft.SqlServer.Management.Smo.Server($instance) $instance = $instance.toupper() $serverName = $serverObject.ComputerNamePhysicalNetBIOS $serverName = $serverName +"\"+$serverObject.InstanceName $serverName