First Use

What is needed:

  • The tinyPFA
  • An oscillator to be measured with preferably a sine wave output at an output level of at least -10 dBm
  • A reference oscillator that has equal or better performance than the oscillator to be measured with preferably a sine wave output at an output level of at least -10 dBm
  • Some attenuators to bring the signal level into the tinyPFA preferably between -10 and -5 dBm but between -20 and 0 dBm will also work with some reduced performance.

How to prepare for measurement:

Frequency calibration (optional step):

  • For frequency calibration of the internal reference apply a input of known frequency and a level around -10dBm to input A, no signal into input B.
  • Set the MEASURE/FREQ to the frequency of the calibration signal.
  • The Level: indicator will show the input level. Start with too much attenuation and reduce the attenuation till "Level:" indicates between -10dBm and -5 dBm
  • Now you will see after "Last A Freq" the frequency of the input signal.
  • To remove any frequency difference activate MEASURE/NULL A FREQ
  • Check if the indicated frequency is now on target, if not, you can repeat nulling the A frequency.
  • The internal reference can be expected to stay within 0.1 Hz of the calibrated frequency. Sufficient for the assessment of the input signals when preparing for accurate measurement

Before frequency calibration:

After frequency calibration:

Assessing the inputs, step 1:

  • The maximum frequency difference that can be measured with high resolution is limited and for the calibration of devices with a possible large frequency error it may be needed to assess if the input frequencies are in range of the high resolution measurement.
  • Connect both sources to the respective inputs ensuring their levels are below 0 dBm
  • Activate DISPLAY/FFT/FFT A (or B) and enable WIDE FFT. Now the spectrum of input A (or B) will be shown within a +/- 37.5 kHz range.
  • To measure the frequency you can either drag the marker to the signal or move the marker to the signal using the left/right function of the jog button.
  • Any frequency deviation larger than 37.5kHz can not be displayed correctly and will create all kind of unexpected problems.
  • Make sure the frequency error is well below 100Hz before proceeding to the next step.

Input signal with -20 kHz frequency error:

Assessing the inputs, step 2:

  • Activate DISPLAY/FFT/FFT A (or B) and disable WIDE FFT. Now the spectrum of input A (or B) will be shown with a +/- 390 Hz range.
  • The actual frequency of the input signal is displayed in the large number behind "Last A(or B) Freq"
  • Make sure both inputs are within 0.1 Hz of each other

Input signal with +9.7 Hz frequency error:

Default measurement setup:

  • Restart the tinyPFA to reset all settings to their defaults. Disabling the FFT mode may work but sometimes it is not sufficient.
  • The default setting with Tau = 0.1 s and Decimation set to 10 should be good starting point.
  • Enable OUTPUT/USB LOG or OUTPUT/DISK LOG if needed
  • With USB LOG enabled and connected to a PC but no program reading the data active at the PC side, the tinyPFA will freeze after some seconds. The menu still works but every button press may take up to two seconds.

Two signal with 0.01 Hz frequency difference:

Highest resolution frequency measurement:

  • Set Tau to 1 s and Decimation to 1
  • Use MEASURE/NULL PHASE to get a phase baseline when measuring two input that should be coherent (frequency difference less than 1 micro Hz)

Two signals with less than 1 micro Hz difference and nulled phase difference: