Hi
> On Oct 25, 2014, at 3:34 PM, Tom Van Baak <[email protected]> wrote: > >> How many hours / days/ months / years had the OCXO been off power before the >> run was started? >> >> How soon after turn on did you start taking data? > > Hi Bob, > > On the ocxo.dat data set, the frequency drift rate was down to just 5e-11 a > day so it's likely the OCXO had been powered for many days, even weeks. I > don't know for sure w/o finding an old log book. The web page says the data > came from "run3004/log50187.txt", which is was a free-running TBolt in > November 2008 measured with a TSC 5120 against a locked HP 58503B. I can > re-run the measurement if you wish. > > Why do you ask? I ask because the most common place I see ADEV changing over time without systematic issues is when they have been off power for a long time. If you warm them up and run them for a while, the ADEV tends to become much more predictable. Bob > I have many data sets here, both with lower drift (e.g., rubidium or masers), > or higher drift, or a variety of phase measurement instruments. Lots of > samples is usually better than few samples, but it doesn't take a lot to pin > the stability of an oscillator down to a couple of dB. > > In some cases, computed ADEV is not a number that gets more precise or more > accurate the more data you collect. You can hit a floor and it starts to > diverge if you collect for too many weeks or months. This is expected. HDEV > would be better. > > An analogy: no one is interested in the mean of 1,000,000 days of earth > temperature data. Yes, it will be a "very precise" number, if you apply the > mindless sqrt(N) rule-of-thumb. But once you get enough data, looking at > periodicity, jumps, outliers, and trends over time is usually far more > important than blindly calculating a simple mean or standard deviation from > an entire data set. > > You can argue all day if the ADEV(tau 1000s) should be 3.7e-12 or 3.75e-12 or > 4e-12. Regardless, it's clearly about halfway between 1e-12 and 1e-11. Below > 1 dB, the rest is what day it is, what hour you started the run, how long you > collected data, or how your lab feels that day. Here's an example of ADEV(tau > 1000) from adev6: > > C:\Tmp>adev6 /a < ocxo.dat 1000 > 1000 0/400000 a 3.706451e-012 398000 > > C:\Tmp>adev6 /a < ocxo.dat 1000 40000 > 1000 0/400000 a 4.100519e-012 38000 > 1000 40000/400000 a 3.912714e-012 38000 > 1000 80000/400000 a 3.736134e-012 38000 > 1000 120000/400000 a 4.413685e-012 38000 > 1000 160000/400000 a 3.050424e-012 38000 > 1000 200000/400000 a 3.692079e-012 38000 > 1000 240000/400000 a 3.367214e-012 38000 > 1000 280000/400000 a 3.223972e-012 38000 > 1000 320000/400000 a 3.742055e-012 38000 > 1000 360000/400000 a 3.897041e-012 38000 > > C:\Tmp>adev6 /a < ocxo.dat 1000 4000 > 1000 0/400000 a 7.804138e-012 2000 > 1000 4000/400000 a 4.085721e-012 2000 > 1000 8000/400000 a 3.368610e-012 2000 > 1000 12000/400000 a 2.890283e-012 2000 > 1000 16000/400000 a 2.408464e-012 2000 > 1000 20000/400000 a 5.823737e-012 2000 > 1000 24000/400000 a 4.127749e-012 2000 > 1000 28000/400000 a 4.310555e-012 2000 > 1000 32000/400000 a 3.375545e-012 2000 > 1000 36000/400000 a 4.166632e-012 2000 > 1000 40000/400000 a 3.052641e-012 2000 > 1000 44000/400000 a 4.718652e-012 2000 > 1000 48000/400000 a 4.238576e-012 2000 > 1000 52000/400000 a 5.275587e-012 2000 > 1000 56000/400000 a 5.695453e-012 2000 > 1000 60000/400000 a 3.669497e-012 2000 > 1000 64000/400000 a 3.107038e-012 2000 > 1000 68000/400000 a 4.863025e-012 2000 > 1000 72000/400000 a 1.882393e-012 2000 > 1000 76000/400000 a 2.395768e-012 2000 > 1000 80000/400000 a 1.606562e-012 2000 > 1000 84000/400000 a 6.180515e-012 2000 > 1000 88000/400000 a 3.201972e-012 2000 > 1000 92000/400000 a 2.023414e-012 2000 > 1000 96000/400000 a 1.515005e-012 2000 > 1000 100000/400000 a 2.343072e-012 2000 > 1000 104000/400000 a 4.249873e-012 2000 > 1000 108000/400000 a 2.676816e-012 2000 > 1000 112000/400000 a 1.656133e-012 2000 > 1000 116000/400000 a 2.411179e-012 2000 > 1000 120000/400000 a 4.081474e-012 2000 > 1000 124000/400000 a 2.997803e-012 2000 > 1000 128000/400000 a 2.095393e-012 2000 > 1000 132000/400000 a 5.760947e-012 2000 > 1000 136000/400000 a 7.075811e-012 2000 > 1000 140000/400000 a 1.769521e-012 2000 > 1000 144000/400000 a 3.358276e-012 2000 > 1000 148000/400000 a 4.893182e-012 2000 > 1000 152000/400000 a 1.936321e-012 2000 > 1000 156000/400000 a 1.578596e-012 2000 > 1000 160000/400000 a 3.601683e-012 2000 > 1000 164000/400000 a 2.287769e-012 2000 > 1000 168000/400000 a 3.073412e-012 2000 > 1000 172000/400000 a 2.291148e-012 2000 > 1000 176000/400000 a 5.813071e-012 2000 > 1000 180000/400000 a 3.669111e-012 2000 > 1000 184000/400000 a 1.766833e-012 2000 > 1000 188000/400000 a 2.527836e-012 2000 > 1000 192000/400000 a 1.982012e-012 2000 > 1000 196000/400000 a 2.387086e-012 2000 > 1000 200000/400000 a 4.483388e-012 2000 > 1000 204000/400000 a 1.825970e-012 2000 > 1000 208000/400000 a 1.405565e-012 2000 > 1000 212000/400000 a 5.431766e-012 2000 > 1000 216000/400000 a 1.325479e-012 2000 > 1000 220000/400000 a 1.874571e-012 2000 > 1000 224000/400000 a 8.372485e-012 2000 > 1000 228000/400000 a 4.277784e-012 2000 > 1000 232000/400000 a 2.616340e-012 2000 > 1000 236000/400000 a 3.765100e-012 2000 > 1000 240000/400000 a 1.840977e-012 2000 > 1000 244000/400000 a 2.921888e-012 2000 > 1000 248000/400000 a 1.532576e-012 2000 > 1000 252000/400000 a 2.774957e-012 2000 > 1000 256000/400000 a 5.713711e-012 2000 > 1000 260000/400000 a 4.725035e-012 2000 > 1000 264000/400000 a 3.428511e-012 2000 > 1000 268000/400000 a 2.549448e-012 2000 > 1000 272000/400000 a 8.913688e-013 2000 > 1000 276000/400000 a 4.408449e-012 2000 > 1000 280000/400000 a 2.503479e-012 2000 > 1000 284000/400000 a 1.883790e-012 2000 > 1000 288000/400000 a 3.782682e-012 2000 > 1000 292000/400000 a 3.132628e-012 2000 > 1000 296000/400000 a 2.913452e-012 2000 > 1000 300000/400000 a 2.021695e-012 2000 > 1000 304000/400000 a 3.370930e-012 2000 > 1000 308000/400000 a 2.043129e-012 2000 > 1000 312000/400000 a 5.285278e-012 2000 > 1000 316000/400000 a 3.020556e-012 2000 > 1000 320000/400000 a 3.454389e-012 2000 > 1000 324000/400000 a 5.324399e-012 2000 > 1000 328000/400000 a 4.481485e-012 2000 > 1000 332000/400000 a 1.773463e-012 2000 > 1000 336000/400000 a 4.372101e-012 2000 > 1000 340000/400000 a 5.504813e-012 2000 > 1000 344000/400000 a 3.117502e-012 2000 > 1000 348000/400000 a 5.678955e-012 2000 > 1000 352000/400000 a 2.934761e-012 2000 > 1000 356000/400000 a 3.119271e-012 2000 > 1000 360000/400000 a 2.867365e-012 2000 > 1000 364000/400000 a 5.534214e-012 2000 > 1000 368000/400000 a 1.696574e-012 2000 > 1000 372000/400000 a 1.954016e-012 2000 > 1000 376000/400000 a 3.051420e-012 2000 > 1000 380000/400000 a 5.290654e-012 2000 > 1000 384000/400000 a 3.908393e-012 2000 > 1000 388000/400000 a 2.984008e-012 2000 > 1000 392000/400000 a 2.348755e-012 2000 > 1000 396000/400000 a 4.209189e-012 2000 > > /tvb > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to 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