3 GPS180SV Features
3 GPS180SV Features
The GPS180SV is using the "Standard Positioning Service" SPS. Navigation messages coming in from the
satellites are decoded by the GPS180SV microprocessor in order to track the GPS system time. Compensa-
tion of the RF signal´s propagation delay is done by automatic determination of the receiver´s geographical
position. A correction value computed from the satellites´ navigation messages increases the accuracy of the
board´s oven controlled master oscillator (OCXO) and automatically compensates the OCXO´s aging. The last
state of this value is restored from the battery buffered memory at power-up.
The GPS180SV has several different optional outputs, including four progammable pulses, modulated / un-
modulated timecode and max. four RS232 COM ports, depending on the hardware configuation. Additionally,
you can get the GPS180SV with different oscillators (e.g. OCXO- LQ/SQ/MQ/HQ/DHQ or Rubidium) to cover
all levels of accuracy requirements.
You can review and change the hard- and software configuration options of the clock with the GPSMON32
application(see corresponding section in this manual).
3.1 Time Zone and Daylight Saving
GPS system time differs from the universal time scale (UTC) by the number of leap seconds which have been
inserted into the UTC time scale since GPS was initiated in 1980. The current number of leap seconds is
part of the navigation message supplied by the satellites, so the internal real time of the GPS180SV is based
on UTC time scale. Conversion to local time and annual daylight saving time can be done by the receiver’s
microprocessor if the corresponding parameters are set up by the user.
3.2 Pulse and Frequency Outputs
The pulse generator of GPS180 generates pulses once per second (P_SEC) and once per minute (P_MIN).
Additionally, master frequencies of 10 MHz, 1 MHz and 100 kHz are derived from the OCXO. All the pulses are
available with TTL level at the rear connector.
Frequency Outputs (optional)
The included synthesizer generates a frequency from 1/8 Hz up to 10 MHz synchronous to the internal timing
frame. The phase of this output can be shifted from -360
◦
to +360
◦
for frequencies less than 10 kHz. Both
frequency and phase can be setup from the front panel or using the serial port COM0. Synthesizer output is
available at the rear connector as sine-wave output (F_SYNTH_SIN), with TTL level (F_SYNTH) and via an
open drain output (F_SYNTH_OD). The open drain output can be used to drive an optocoupler when a low
frequency is generated.
In the default mode of operation, pulse outputs and the synthesizer output are disabled until the receiver
has synchronized after power-up. However, the system can be configured to enable those outputs immedi-
ately after power-up. An additional TTL output (TIME_SYN) reflects the state of synchronization. This output
switches to TTL HIGH level when synchronization has been achieved and returns to TTL LOW level if not a
single satellite can be received or the receiver is forced to another mode of operation by the user.
3.3 Time Capture Inputs
Two time capture inputs called User Capture 0 and 1 are provided at the rear connector (CAP0 and CAP1) to
measure asynchronous time events. A falling TTL slope at one of these inputs lets the microprocessor save the
current real time in its capture buffer. From the buffer, capture events are transmitted via COM0 or COM1 and
displayed on LCD. The capture buffer can hold more than 500 events, so either a burst of events with intervals
down to less than 1.5 msec can be recorded or a continuous stream of events at a lower rate depending on the
GPS180SV
Date: 21st June 2017
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