How do I get AvgDiskSecPerWrite to return the same value as the object in perfmon instead of 0?

Question

I am trying to query WMI to get the value for AvgDiskSecPerWrite from Win32_PerfFormattedData_PerfDisk_PhysicalDisk using WQL with the following query

SELECT AvgDiskSecPerWrite FROM Win32_PerfFormattedData_PerfDisk_PhysicalDisk 

but it always returns 0, if I view the same counter in perfmonitor I am getting values like 0,002. How can I query WMI to get this value? The machine I am trying this on is running windows server 2003