Document Title:
11
User’s Manual for the GPS Orion-S/-HD Receiver
Document No.
Issue 1.0
GTN-MAN-0110
June 22, 2003
DLR/GSOCNo part of this document shall be reproduced in any form or disclosed to third parties without prior authorization.
3.1.6 Pulse-per-Second Signal
Supporting receiver versions provide a one-pulse-per-second signal (CMOS TTL level) at pin
10 of the interface connector. The PPS signal is available in case of valid navigation. It has a
one millisecond duration and its starting edge is aligned to the occurrence of an integer GPS
second with an accuracy of better than 1
µ
s. The typical error amounts t ca. 0.2
µ
s and is
determined by the limited resolution of the correlator timing (175 ns) and the accuracy with
which the modelled GPS time of the receiver matches the true GPS system time (<0.1
µ
s
with S/A off). When using long antenna cables in ground based tests, the PPS will experi-
ence a systematic shift in accord with the added signal time.
Irrespective of the availability of an output pin for the PPS hardware signal, the measure-
ments and navigation solution of the receiver are aligned to the integer GPS second when-
ever a continuous 3D navigation solution has been achieved.
3.1.7 Troubleshooting
If deemed necessary, various electrical and functional checks may be performed at any time
to validate the proper receiver operation:
•
The product of the supply voltage and current consumption shall match the nominal
power consumption of 2.4±0.1W. A lower value may indicate errors in the boot proc-
ess caused by e.g. twisted EPROMs or a broken address/data line on the main
board.
•
When connected to a terminal program, the receiver shall output a continuous stream
of (mostly numeric) ASCII characters. Failures to do so may indicate problems with
the physical connection (e.g. twisted RX/TX lines of the serial cable) or a wrong con-
figuration (baud rate, etc.) of the PCs COM port.
•
The receiver shall respond to commands (for a simple test, try the <STX>DR00-
10A<ETX> and <STX>DR000117<ETX> commands to toggle the F00 message out-
put). Failures may again indicate problems with the physical connection or the com-
munication software.
•
With adequate open sky visibility the receiver shall achieve code lock (“C”) with an
SNR value of better than 10 dB on (at least) one channel within a maximum of 5 min
irrespective of its initialization state. Otherwise, problems in the antenna system (pas-
sive versus active antenna, inappropriate or erroneously connected pre-amplifier,
broken antenna cable, etc.) may be suspected.
•
If other problems in the antenna system can be ruled out, one may further verify that
the center pin of the antenna connector has a DC level of +5.0±0.1V with respect to
ground.
In case of persistent failures inspection by the manufacturer may be required.
