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Revision A
Model 340 Telemetry System
5-9
2006920-001
Calibration: Receiver Calibration
6.
Refer to
. Confirm each tone decoder output locks. The
output will go to a logic low state when a 50 mVRMS sine wave of
proper frequency is applied to each input at pin 3 of each IC.
7.
Ground TP18. Confirm TP30 goes to a low with the presence of the
20 Hz mode tone.
8.
Remove the 20 Hz tone. Confirm TP31 goes to a low with presence of
2600Hz subcarrier only, with 1.0 Vp-p at TP 45.
RF Carrier Detect
1.
Disconnect the UHF receiver module at J6. Connect the positive lead
of a 0 to +5 Vdc adjustable voltage source to J6 pin 3. Connect the
negative lead of the variable voltage source to J6 pin 5. Set R1 fully
clockwise (wiper at +5 Vdc). Set the variable voltage source to +2.0
Vdc. Observe the following: the signal indicator is off, and a high
signal is on J4 pin 3. Adjust R1 counter-clockwise until TP1 goes
low. Observe that the signal indicator flashes at approximately 1-
second intervals. Increase the voltage from the variable voltage
source until the signal indicator stops flashing and remains
illuminated. Confirm the voltage source is at +3.0 ± 0.45 Vdc.
127(
R1 may need to be readjusted with the UHF receiver module
reconnected to J6.
2.
Remove the voltage source while observing TP1. TP1 should go high
between 0.2 and 0.8 seconds after the voltage source is removed.
3.
With TP1 low, confirm the weak battery indicator signal located on
J4, pin 5 flashes at approximately 1-second intervals with TP12 and
TP7 jumpered to ground. Confirm the indicator illuminates
continuously with only TP1 and TP12 low, and is off if TP1 or TP12 is
high.
Table 5-4. Tone Decoder Output Locks
Input
C Reference
Input
Center Frequency and Voltage
Output
Test Point
U26-3
10 Hz at 50 mVRMS
TP7
U28-3
20 Hz at 50 mVRMS
TP47
U14-3
40 Hz at 50 mVRMS
TP48
U21-3
80 Hz at 50 mVRMS
TP12
DC
VOLTS
DC SUPPLY
↑
↑
Содержание Corometrics 340
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