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the survey, the System can measure and then compensate for their effects using the Background
Compensation facility.
Summary:
1. Perform the Background Compensation procedure described in
Compensation and Monitoring" on page 6-14
vals of 30 minutes.
2. Avoid using manipulators and probes during a survey, and ensure that those parts of the ROV
close to the coil array cannot move.
7.2.2.2 Power-carrying Cables
If you use the 440 System to survey power cables that are carrying high currents, the coils might
experience some interference. If this occurs, random errors may appear in measurements supplied by
the System.
The most effective way to cure this problem is to remove power from the target cable.
Summary:
1. Perform regular checks on signal quality by using the SDC oscilloscope function. Determine
whether any electrical noise is present on the received signal. If the noise does not enter either
of the sampling regions shown on the oscilloscope display you may ignore its effects.
2. If noise is present on the oscilloscope display and it is affecting measurements, arrange to
remove power from the cable before you continue the survey.
7.2.2.3 Impressed-current Cathodic Protection
The 440 System may suffer from noise pick-up if you use it to survey pipes that use single-phase
impressed-current cathodic protection. This will generate random errors in the range and offset data.
Use the SDC oscilloscope function to check whether there is noise on the signal from this source.
Three-phase impressed current protection and pipes protected by sacrificial anodes do not affect the
440 System in this way.
Summary:
1. Use the SDC oscilloscope function to make regular checks on signal quality.
2. If necessary, arrange to switch off the impressed-current protection. The interference will dis-
appear immediately but the protection afforded by the current will remain for several days.
7.3 ROVs
You may use the 440 System with most types and size of ROV, and you may operate it at depths down
to its specified depth rating listed in
described in this Manual provides a high degree of accuracy and a useful measurement range,
together with ease of deployment.
It is important to install the 440 System properly by following the instructions included in
"Physical Installation"
and
valid survey data only if you follow the installation and operating instructions in this Manual. Provided
you follow these instructions, you may install the System on most types of ROV.
DPN 402196 Issue 4.1
Chapter 8 "System
Chapter 4 "Electrical Installation"
© Teledyne TSS
7 – Operational Considerations
section 6.3.3 "Background
before the survey commences and then at inter-
Specifications". The standard installation
of this Manual. The System will supply
Chapter 3
7- 7
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