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5-6
Model 340 Telemetry System
Revision A
2006920-001
Calibration: Receiver Calibration
TOCO Channel
1.
Confirm the –3dB points of the band-pass frequency from the input
at TP45 to the output at TP29. The lower 3 dB point should measure
between 1250 and 1650 Hz. The upper 3 dB point should measure
between 1900 and 2250 Hz. The gain at TP29 is 2 at the center of the
bandpass.
2.
With input frequency at TP45 set to 1750Hz and 250 mVp-p, adjust
R73 until the dc voltage at TP3 is equal to the dc voltage at
TP4 ± 10 mVdc.
3.
With the input frequency switched between 1750 Hz and 1505 Hz,
adjust R89 for a voltage differential at TP20 of 4.14 ± 0.1 Vdc.
127(
The low frequency response of this output stage is
approximately 0.1 Hz. Allow the stage time to settle between
frequency shifts. The scale factors for the TOCO stages are
27.2 mV/mm and 16.3 mV/Hz at TP20. Any input frequency
shifts can be used to achieve these scale factors.
4.
Confirm frequency response at TP20 is dc to 0.1 ± 0.02Hz.
5.
Confirm the PLL lock-in range. This is the frequency where it
first achieves lock, not the range over which it maintains lock.
PLL lock occurs at
≥
1300 Hz and
≤
2200Hz. Confirm lock occurs at
1300–1520 Hz and 1970–2420 Hz. Lock-in is verified by a logic low
at TP5.
dB
UNITS
AC
VOLTS
888 888 888
Hz Generator
888 888 888
Hz Counter
Содержание Corometrics 340
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