Integrators Guide - Light 95
© 2018 Nortek AS
temperature the clock drift is likely to be even smaller. At 8 Hz sampling rate, this will be 1/10 of a
sampling interval over one hour of measurements.
Figure: Description of sync and sampling and data out intervals
Output of the Vector system data (compass, tilt and temperature) is not synchronized between
different Vectors through the use of the SyncIn signal. Instead, the start on the sync edge that is
present in both synchronization modes is used to start the 1 Hz output of the system data. Each
Vector will then output its system data based on its internal real time clock. This implies that the
number of system data outputs may vary slightly from one instrument to another. Note that this is
not a problem for the synchronization of the velocity measurements. The compass and tilt data are
used internally in the Vector to ensure correct transformation of the velocities to earth coordinates
when ENU is selected as coordinate system. In detail, each Vector configured for Start on Sync will
output system data in a certain order at the start of continuous measurement and at the start of
each burst when configured for burst measurements. The system data are output in the following
order:
1. Output header containing noise measurements and date/clock.
2. Output one sample of system data.
3. Wait until external trigger is detected and then start to output system data at a 1 Hz rate based
on the local clock. Velocity data will be output according to the configured synchronization
scheme.
Specifications of Signal Levels
The SyncIn input voltage must be between 0 V and 5.0 V. The SyncIn is a Schmitt Trigger input with
a pulldown resistor of 100kΩ to ground. The input threshold values for the SyncIn are:
Vt+ input positive threshold, 2.2 V
Vt– input negative threshold, 0.9 V
Figure: Inout threshold values for SyncIn
The output voltage levels for the SyncOut are:
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