if you need an acccurate value for your clock never probe the clock directly because the probe capacitance will alter your clocks actual preformance -in some cases it will make a marginal clock fail in others it may improve it, but to get real data measure a derived known signal and extropolate back for the operating frequency. Those 30 pf caps both insure startup and load the crystal. The manufacturerspecifies them and factors this in when he cuts the quartz. Changing them affects startup, frequency, stability and output wave quality. Hope this helps Terry