A radio frequency probe analysis system comprising: a sampling unit arranged to generate digital power signals (26a, 26b, 50a, 50b) based on a plurality of analog signals (28, 30) including an analog voltage signal and an analog current signal characterizing power delivered from an RF power delivery system to a plasma chamber; the sampling unit including a first filtering module arranged to band limit the analog voltage signal and the analog current signal to a first predetermined bandwidth, the first predetermined bandwidth including a first plurality of frequencies; and a primary A/D converter coupled to the first filtering module, the primary A/D converter being arranged to generate a first digital voltage signal based on the analog voltage signal and to generate a first digital current signal based on the analog current signal, the first digital voltage signal and the first digital current signal being synchronised and defining the digital power signals; the sampling unit further including a second filtering module arranged to band limit the analog voltage signal and the analog current signal to a second predetermined bandwidth, the second predetermined bandwidth including a second plurality of frequencies; a secondary A/D converter coupled to the second filtering module, the secondary A/D converter being arranged to generate a second digital voltage signal based on the analog voltage signal and to generate a second digital current signal based on the analog current signal, the second digital voltage signal and the second digital current signal being synchronised and further defining the digital power signals; a digital-processing unit arranged to generate a digital power spectrum signal based on the digital power signals; said sampling unit being arranged to simultaneously sample the first plurality of frequencies from the analog signals (28, 30) and to further simultaneously sample the second plurality of frequencies from the analog signals (28, 30) such that the digital spectrum signal defines signal levels for the first plurality of frequencies and further defines signal levels for the second plurality of frequencies. a sampling unit arranged to generate digital power signals (26a, 26b, 50a, 50b) based on a plurality of analog signals (28, 30) including an analog voltage signal and an analog current signal characterizing power delivered from an RF power delivery system to a plasma chamber; the sampling unit including a first filtering module arranged to band limit the analog voltage signal and the analog current signal to a first predetermined bandwidth, the first predetermined bandwidth including a first plurality of frequencies; and a primary A/D converter coupled to the first filtering module, the primary A/D converter being arranged to generate a first digital voltage signal based on the analog voltage signal and to generate a first digital current signal based on the analog current signal, the first digital voltage signal and the first digital current signal being synchronised and defining the digital power signals; the sampling unit further including a second filtering module arranged to band limit the analog voltage signal and the analog current signal to a second predetermined bandwidth, the second predetermined bandwidth including a second plurality of frequencies; a secondary A/D converter coupled to the second filtering module, the secondary A/D converter being arranged to generate a second digital voltage signal based on the analog voltage signal and to generate a second digital current signal based on the analog current signal, the second digital voltage signal and the second digital current signal being synchronised and further defining the digital power signals; a digital-processing unit arranged to generate a digital power spectrum signal based on the digital power signals; said sampling unit being arranged to simultaneously sample the first plurality of frequencies from the analog signals (28, 30) and to further simultaneously sample the second plurality of frequencies from the analog signals (28, 30) such that the digital spectrum signal defines signal levels for the first plurality of frequencies and further defines signal levels for the second plurality of frequencies.