Teledyne 440, System Manual, Page: 133 / 256

6 – Operating Procedure
DPN 402196 Issue 4.1 © Teledyne TSS 6- 29
accommodate the additional resolution. There are several conditions that will
cause the field to contain question marks:
❐ The target is out of range
❐ The 440 System cannot compute an accurate position for the target
❐ Coil saturation has occurred
NOTE
Although the VRT measurements displayed and logged will be valid to the top of
the weight coating, the 440 System always measures to the top of the conductive
part of the target. The SDC compensates for the thickness of any weight coating
and outputs the corrected value. See Figure 6-3 and Figure 6-4.
11. Coil altitude (ALT) information comes from an altimeter if the System includes one. Otherwise,
the information in this field will be the fixed coil height if available. The field will contain ques-
tion marks if there is no fixed height or altimeter information available. If millimetre resolution is
used the field length will be increased by one character to accommodate the additional resolu-
tion.
12. The SDC calculates the target depth of cover (COV) using COV = VRT – ALT. A positive value
indicates the target is covered. Zero or negative values indicate an exposed target. If millimetre
resolution is used the field length will be increased by one character to accommodate the addi-
tional resolution. There are several conditions that will cause the field to contain question
marks:
❐
The target is out of range
❐
The 440 System cannot compute an accurate position for the target
❐
Coil saturation has occurred
❐
There is no fixed coil height or information available to the SDC from an altimeter
C) Timestamped Coordinates Format
The timestamped coordinates data contains the standard coordinates data format as outlined in Table
6-4 . In addition, the packet contains a timestamp to identify when new data has been received and a
checksum to verify the packet integrity. The data format is described in Table 6-5
Table 6-5: Timestamped Coordinates format