Measure-Website-Performance.ps1

[CmdletBinding()]
param (
    [string]$Url = "http://my-url.com",
    [int]$Interval = 1
)

$csvPath = "$PSScriptRoot\Performance $(Get-Date -Format 'yyyy-MM-dd HH-mm-ss').csv"

while ($true) {
    $start = Get-Date
    $duration = Measure-Command {
        $response = Invoke-WebRequest $Url
    }

    $log = ([PSCustomObject]@{
            Start            = $start
            Duration         = [Math]::Round($duration.TotalMilliseconds)
            RawContentLength = $response.RawContentLength
        })

    Write-Output $log

    $log | Export-Csv -Path $csvPath -Append -NoTypeInformation -Delimiter ";" -Encoding utf8BOM

    Start-Sleep -Seconds $Interval
}