AVIATION RECORDERS
OPERATOR'S MANUAL
MODEL FA2100GSE
PORTABLE INTERFACE (PI)
Rev. 01 Page 5
−
15
May 01/99
CVDR Operation
5.3.4
Rotor Speed FSK Data
Rotor Speed output data is displayed (in Hz) on the following PI menus:
D
Playback Menu
D
File Playback Menu
D
Can be selected for display from the Special Functions Menu.
Rotor Speed FSK data is output by the PI each time a new rotor speed value is available.
The bit rate is 768 bit/sec
5% with the LSB transmitted first. The Rotor Speed FSK level
is 2 vrms
−
122 vrms, differential input.
A “1” bit is represented by a frequency of 4193
30 Hz.
A “0” bit is represented by a frequency of 3607
30 Hz.
To ensure synchronization by ground based equipment, the input label (Bits 1
−
8) are set to
“0” and Bit 9 is set to “1”. Bits 10
−
12 are set to “0”. Bits 13
−
20 represent the reference
count and bits 21
−
32 represent the rotor pulse count. These counts are output as present-
ed by the FA2100 over the GSE TDM bus, words 24 and 25. The output signal has an
output impedance of 20 ohms maximum and a signal level of 2.45 Vrms +10% across a
load impedance of 600 ohms.
/TC_INH
(enable)
TC
32 / 768 Sec
32 bits of data (1 bit = 1 / 768 Sec)
.
.
.
FSK
.
.
.
ONCE EVERY FOUR (4) SECONDS
Mark (1) = 4193 + 30Hz
Space (0) = 3607 + 30Hz
Figure 5
−
4.
GMT FSK And Rotor Speed FSK 32
−
bit Format
Rotor Pulse Frequency = (400 Hz) x (Rotor Pulse Count) / (Reference Count), or
Rotor Pulse Frequency = 400 x Word 2 / Word 1.
For displaying rotor speed the user must be able to select the display to be frequency or
calculated revolutions per minute (RPM). To allow the conversion from frequency to RPM
the user must provide a matching frequency to RPM ratio. For example, 6 kHz = 300
RPM. To determine the calculated RPM use the following formula:
RPM = Rotor Pulse Frequency x (Rotor RPM/Tach Frequency).
Rev. 04 Page 5
−
15
June 01/04