This calculator was created to give an approximate value for measurement
error based upon the values entered. Input the frequency to be measured
(in Hz), then select the timebase, the model of the frequency counter,
and the arming (triggering) mode to be used. You can view the assumptions
made in calculating the measurement error by selecting Assumptions below
"THE MEASUREMENT ERROR" result.
Select Assumptions for details in calculating Total Measurement Error and Time Base Error.
Select Details to show values for Time Base Error, RMS Resolution, Systematic Uncertainty, and LSD (Least Significant Digit) Displayed, which will help if you wish to follow and/or customize the formulas given in the manuals and data sheet.
The following assumptions have been made:
Total Measurement Error = Systematic Uncertainty ± s * RMS Resolution Measurement Error has been computed to within 2-sigma confidence (ie s = 2).
A 1 year Time Base Error, assuming the instrument is operating within the specified temperature range and a 1 year specifications for the aging rate (ie Time Base Error = Temperature Stability + Daily Aging Rage * 30 days + Monthly Aging Rate * 11 Months). A lower time base error can be used for the time leading up to the calibration and just after calibration. See Tips for making more accurate measurements with a frequency counter.
The formulas for Systematic Uncertainty and RMS Resolution are given in the manuals and data sheet. The typical values for tres, tacc, and tjitter provided in the manuals and data sheet have been used in this calculator.
It has been assumed that the trigger error is negligible compared to the total measurement error. If the input signal is noisy, the trigger points that define the beginning and end of a measurement may be advanced or delayed. The resulting timing uncertainty is a function of the slew rate of the signal and the amplitude of spurious noise spikes.
It is assumed the trigger is set to auto trigger at a 50% level.
It is assumed the instrument is calibrated and operated in accordance to good metrology standards.