
D – ALTIMETER
DPN 402197 © TSS (International) Ltd Page 11 of 18
The serial data is converted to RS232 levels in the digital section where the usual pro-
tection diodes etc. are situated.
The +12VDC for the RS232 interface is derived from the transmitter +12VDC and the
minus -12VDC from a +12VDC to -12V DC-DC converter circuit.
D.3.2.6 Averaging Algorithm
The microcontroller uses a moving weighted averaging algorithm to ensure that any
momentary noise or interference from the Sonar signal does not appear as a range at
the data output. This is achieved by giving each new range a weight of 25% while the
previous range is given a weight of 75%. If the new range differs significantly from the
old the new range will be replaced with the old. If more than two unacceptable ranges
are received the next new range is accepted. Each new range occurs approximately
0.2 second apart.
D.3.2.7 Optional Modem
Position IC1 is for an optional modem module. This module receives the serial data
from the altimeter and superimposes the data on to the +24VDC power cable; this
allows the altimeter to connect using just two cable cores over long cables using FSK
modem technology. To use this option the power supply must be +24VDC. Switch S1
switch 3 and switch 4 to the on position to select 9600 baud and dc-dc converter
inhibit.
D.4 PART NUMBERS
Table D–5: Part numbers
500292 Altimeter, subsea TSS-ALT-250 (no cable or accessories)
500294 As above, detection kit (includes bracket 601824A)
500295 Altimeter, including 3m pigtail 601826A
601824A Cable ALT-250 to TSS 350/440 SEP (3m)
601825A Cable ALT-250 to TSS 350/440 SEP (7m)
601826A Pigtail (3m)
601827A Pigtail (7m)
402321 Separate manual
307558 O-Ring
402608 Carton
200809 Mini wet-pluggable free lead, LPMIL-7-MP200809
305676 Mounting kit
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