P788x Oscillator Selection
|
Our ultra-fast TOF/Multiscaler/Photon Counters of the P788x-Series are normally equipped with a standard 10 MHz quartz reference oscillator. The requirements for the reference oscillators quality depend on the selected sweep length - the longer the sweep lengths the better the reference oscillator has to be.
What do we offer ?
We offer 10 MHz reference oscillators with tighter specifications as an option.
- Standard Quartz Oscillator: <100 ppm over temperature range
- Temperature compensated QO +/- 1ppm (P7889 only)
- Ovenized QO +/-0.03 ppm over t emperature rangel
- Rubidium Oscillator +/-0.00005 ppm over temp.
How to select the right oscillator ?
One has to calculate the relative accuracy of the clock and compare it to the relative channel resolution. Both numbers should be about equal (if possible).
Examples: (calculated for an ambient temperature variation of 10 deg C)
1) P7888: (1ns time res.), 10.000 time bins / sweep:
relative resolution is 10.000 to 1. (10 µs)
normal oscillator: 50 ppm x 10 deg = 500ppm = 1 / 2000 (max).
typ: 100ppm over temp range: 1/10.000
conclusion: the normal reference oscillator should be ok.
2) P7888: (1ns time res.), 1.000.000 time bins / sweep:
relative resolution is 1.000.000 to 1 (1 ms)
normal oscillator: 50 ppm x 10 deg = 500ppm = 1 / 2000 (max).
typ: 100ppm over temp range: 1/10.000
conclusion: normal ref oscillator is 100 times worse than the time bin resolution.
oven oscillator: 0,03 ppm (over temp range) = 1 / 30.000.000 ageing: 0,2ppm over one year
conclusion: oven ref oscillator is ok up to 30.000.000 time bins (30ms for the P7888).
(5.000.000 time bins for long term measurements)
3) P7889: 100ps time res., 100.000 time bins / sweep:
relative resolution is 100.000 to 1. (10µs)
improved quartz oscillator: 1 ppm (over temp range) = 1 / 1.000.000
conclusion: improved ref oscillatorshould be ok.
4) P7889: 100ps time res., 10.000.000 time bins / sweep:
relative resolution is 10.000.000 to 1 (1 ms)
improved quartz oscillator: 1 ppm (over temp range)= 1 / 1.000.000
conclusion: improved ref oscillator is not ok.
oven oscillator: 0,03 ppm (over temp range) = 1 / 30.000.000 (ageing: 0,2 ppm over one year)
conclusion: oven ref oscillator is ok up to 30.000.000 time bins (3ms for the P7889).
5) P7889: 100ps time res., 10.000.000.000 time bins / sweep:
relative resolution is10.000.000.000 to 1 (1 s)
improved quartz oscillator: 1 ppm (over temp range) = 1 / 1.000.000
conclusion: improved ref oscillator is not ok.
oven oscillator: 0,03 ppm (over temp range) = 1 / 30.000.000 (ageing: 0,2ppm over one year)
conclusion: oven ref oscillator is not ok.
Rubidium oscillator: 0,00005 ppm (over temp range) = 1 / 20.000.000.000 (ageing: 0,0001ppm over one year)
conclusion:: Rubidium oscillator is ok up to 100.000.000.000 time bins (10s for the P7889).
SUMMARY
for sweep length up to: use:
20.000 time bins normal quartz oscillator.
1.000.000 time bins improved osc. (P7889).
30.000.000 time bins ovenized quartz oscillator.
100.000.000.000 bins Rubidium oscillator
