Fróðskaparrit - 01.01.1993, Page 149

MEASUREMENTS OF SEA BOTTOM TEMPERATURES
153
1.5 times the bottom depth. From the be-
ginning the cable was deployed with con-
siderable slack and cable breaks often tend-
ed to occur at the same sites so that the
slack from previous splicings could be re-
moved; but during the period the cables did
change in length several times. This was
documented by the “Splicing-list” from the
ship which was updated after each splicing.
For each section of cable the list showed
the length, the weight, detailed cable con-
struction, core resistance at 24°C and ca-
pacitance in addition to the time of final
splicing and miscellaneous information.
During the second World War cable repair
was performed by British ships and for this
period the splicing lists were not always re-
ported. Thus there are gaps in the measure-
ments during the war period.
Resistance measurement
The resistance measurements were initiat-
ed primarily to monitor the state of the ca-
bles and in addition to resistance, the ca-
pacitance and isolation resistance were also
monitored. From the beginning the mea-
surements were made on the fírst sunday of
every month so that 12 annual measure-
ments were obtained except for periods of
cable break. At the end of 1942, however,
this was changed to the fírst sunday of
every third month as the British navy would
not accept the 2-hour disruption in commu-
nication required for the measurements.
After the war the reduced measurement fre-
quency was retained.
The measurements were performed in
Tórshavn while the cables were grounded
■<200m r [[j00-500m ' □ 500-1000m □ >1000m
Fig. 2. Cable track and bottom topography for the two
cables.
in Iceland and Shetland respectively quite
close to the landing points. Resistance of
the Iceland-cable was also measured from
Iceland, but these values are not presented
here. Resistance was measured using a
Wheatstone Bridge with a reflecting gal-
vanometer of type “Sullivan”. Such a mea-
surement is sensitive to various disturban-
cies including slowly varying and rapidly
varying earth current. The measurement
procedure was adapted to this and always
included two different types of measure-
ment; using “false zero” and the “Rolland
Black” method respectively. The details of
these methods are described in the manual:
“Lærebog i maalings-teknik vedrørende
søkabler m.m.” published by SNTS
(Copenhagen, 1934). The values presented
here are from the “false zero” measure-