Instruction manual
MXS-EVO - MANUAL
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MXS-EVO – Manual – Rev 1.7 - 39 -
Press the Save Screen button and specify a file on which to save the data. The acquisition is now started and ends when
the utility is closed. If the Continuous save field is not enabled is possible to press Save Screen in order to save the data
currently acquired (it may slow down the PC if there is much data to save).
The resulting file is a simple csv that may be edited and viewed by a commond spreadsheet program (e.g. Microsoft
Excel).
Follows the complete list of all the values that are exported:
Time number of seconds since epoch (1st January 1970)
SRC num number of reference (1 GPS, 2 EXT, 3 E1, 4 PTP, 5 IRIG-B)
PPS jitter (ns) short-term stability of the source PPS
Vtune corrente current vtune value of the OCXO
PPS distance (ns) distance of the source PPS against the reference PPS
holdover num (s) number of seconds from which the device is not disciplining
Vtune stabile last stable vtune
Sync num number of PPS resyncs
Antenna status antenna status (0 OK)
T-RAIM solution PPS status (0 OK)
T-RAIM alarm (ns) maximum distance of the reconstructed PPS in order to be considered valid
T-RAIM error (ns) GPS PPS accuracy
GPS error GPS PPS error
Visible sats number of visible satellites
Tracked sats number of tracked satellites
Quality factor quality factor (based on the GPS antenna, > 25 OK)
need_pps_reset (internal use)
need_pwm_duty_stable (internal use)
pps_polarization (internal use)
pwm_speed_limit (internal use)
Sync done * locked
Master <- currently selected source
Is suggested to:
1. Collect the data as previously explained in .csv format (using Continuous save option)
2. open Excel and apply an automatic filter on the 2nd column (the one of the source number with the #)
3. initially filter based on source #1 (GPS) and verify that the 5th column (PPS distance) would contain values
near 100 ns (the base unit is the ns)
4. subsequently filter based on the other sources #2 (EXT), #3 (E1), #4 (PTP) o #5 (IRIG-B) and plot the 5th
column (it shows the precision of the reconstructed PPS).
D: Is it possible to reach NTP stability below 1 ms?
R: Yes. In order to achieve sub-ms precision it is necessary to enable the NTP hardware timestamping support. In this
way is possible to have timestamps accurate to better than 100 ns.
Please note that the client device should be able to cope with the interleaved mode (please refere to NTP section for
further details).
In Windows Vista and Seven a few additional steps may be required to improve the performance:
• Disable CPU spread spectrum capabilities in the BIOS
• Disable CPU frequency scaling capabilities
• Set the following environmental variable:
NTPD_USE_INTERP_DANGEROUS=1
If nothing works you it may also possible to try with the serial port. The device outputs a NMEA stream @ 9600 bps
8/N/1 and triggers the PPS on pin 1 (DCD)
The following configuration may be used in ntpd.conf:
server 127.127.20.1 minpoll 4 maxpoll 4 mode 24 # NMEA @ 9600 bps, $GPZDA
fudge 127.127.20.1 time2 0.0110185 # time correction
A NULL modem cable should be used to connect with the device on the serial port.