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After installing 18x-LVC, the NTPClockOffset is in a much improved range, from -70 to 25 microseconds:
. NTPFreqOffset is also in a much tighter range, indicating that NTP is applying smaller corrections to the system clock. GPSdiff is also much better behaved, ranging from a minimum of 0.5 to 1.1 seconds. The number of satellites tracked by the new GPS is also generally higher.
Temperature Effects
The frequency offset shows a temperature dependence in the system clock oscillator. We do not measure the temperature inside the data system box enclosure, which is at the base of the tower. The nearest temperature measurement is of the ambient air at 2 meters up the tower. The top panel in the plot below shows a time series of the air temperature, along with NTPFreqOffset, for a cool 3 day period in April, after the installation of the new GPS. It appears that when the air temperature is below 5 deg C, the system clock oscillator does not show an obvious temperature relation.
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