Tente usar o comando Get-Counter
que extrai os dados do monitor de desempenho do sistema. Para o seu exemplo, ficaria assim:
# ~> Get-Counter "\Process(ProcessName*)\% Processor Time" | select -expand countersamples
Um exemplo, usando chrome:
# ~> Get-Counter "\Process(chrome*)\% Processor Time" | select -expand countersamples
Path InstanceName CookedValue
---- ------------ -----------
\machinename\process(chrome#7)\% processor time chrome 0
\machinename\process(chrome#6)\% processor time chrome 0
\machinename\process(chrome#5)\% processor time chrome 0
\machinename\process(chrome#4)\% processor time chrome 0
\machinename\process(chrome#3)\% processor time chrome 0
\machinename\process(chrome#2)\% processor time chrome 0
\machinename\process(chrome#1)\% processor time chrome 0
\machinename\process(chrome)\% processor time chrome 3.10141153081511