Serial Data Format - Cygnus 1 Operation Manual

SERIAL DATA FORMAT

CygLink program is provided to automatically decode the measurement data sent from the
Gauge, and to provide a calibrated display of the results
For users who want to display and log the data using their own software : this describes the
arrangement of the data sent from the Gauge
Data Communication Format
Data Output Standard
Differential RS-422 line drivers [TX+, TX-]
Unidirectional - Gauge is transmit only
Data-byte Format
8 Data bits, 1 Start bit, 1 Stop bit, No Parity; 2400 baud
Data-Packet Arrangement
4 packets per second
Valid-Reading packet-length
No-Reading packet-length
Interpreting the Reading sent from the Gauge
Scaling
The Gauge takes measurements using an accurate fixed-rate crystal oscillator
Readings are scaled for an equivalent Velocity of Sound of 6400 m/s
Displayed readings have to be scaled by multiplying by the Velocity of Sound (in
m/s) for the Material-under-Test, and then dividing by 6400
Decimal Point position is implied from the combination of Range, Resolution, and
Units bits in the Status byte of each Reading [see table below]
Range
The Gauge returns all Readings in a 4-byte decimal string
Readings which require 5-bytes [eg 100.00+mm, or 10.000+inch] are autoranged to
the 4 most significant bytes
Range bit for every Reading must be read from the Status-byte
Resolution
The Gauge has a default Hi-Resolution setting : 0.05 mm, or 0.002 inch
Lo-Resolution setting is not normally used : 0.1 mm, or 0.005 inch
Resolution bit must be read from the Status-byte
Units
The Gauge has a default Metric Units-setting
Units bit must be read from the Status-byte
: 7 bytes
: 3 bytes
Introduction
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