$logpath = "C:\PerfLogs\Admin\ServerManager\*.blg"
$perfcounter = "*Processor(_Total)\% Processor Time*"
#$perfcounter = "*Memory\Available KBytes*"
$intervalhr = 1

$since = (Get-Date).AddHours(-1*$intervalhr)
$logs = Get-ChildItem $logpath |
    Where-Object { $_.LastWriteTime -ge $since } |
    Sort-Object LastWriteTime -Descending

$counters = @()
foreach ($log in $logs) {
  $ret = $null
  if((get-item($log)).Length -gt 131072) {
    $ret = Import-Counter -Path $log.FullName -ErrorAction SilentlyContinue | Where-Object { $_.TimeStamp -ge $since } | Select-Object -Expand CounterSamples
    if ($ret -and $ret.Count -gt 0) {
      $counters += $ret
    }
  }
}
if ($counters) {
  $usage = $counters | Where-Object Path -like $perfcounter
  if($usage) {
    $result = $usage |Measure-Object -Property CookedValue -Average -Maximum -Minimum
    "AVG: {0:N2} MAX: {1:N2} MIN: {2:N2}" -f $result.Average,$result.Maximum,$result.Minimum
    #return $result.Average
  } else {
    Write-Host "No performance data in logs."
  }
} else {
  Write-Host "No performance data in logs."
}