Circuit Description
85
SR620 Universal Time Interval Counter
temperature control can provide 0 to 26 Vdc to the
fan.
Thermal control of the fan speed has several
advantages, including, quieter operation, longer
fan life, faster warm-up, and lower overall
temperature coefficients for the instrument.
POWER SUPPLY BYPASS
(Sheet 15 of 16)
The 60 bypass capacitors for the +5, -5.2, -2, and
+/-15 Vdc power supplies are shown on this page.
These capacitors are distributed around the PCB:
they bypass portions of the power plane to the
ground plane (inside PCB layers).
Unused portions of IC's are also shown on this
page.
FRONT PANEL DISPLAY PCB
(Sheet 16 of 16)
The front panel display PCB holds 16 seven
segment displays (U1-16), 75 LED lamps, and 32
conductive rubber keys. All of the driver circuits
are located on the main PCB (sheet 4 of 16).
The PCB is a double sided, gold plated, glass-
epoxy board. The gold plating is required for long
term reliability of the rubber keypad.
All of the LED's are refreshed for 2 ms with a 1:8
duty cycle. One of the strobe lines, Stb0 to Stb7, is
held high to refresh a pair of seven segment
displays and a column of 10 LED lamps. The
particular segments and lamps in the strobe
column are turned on by grounding the cathode of
the LEDs through a current limiting resistor on the
main PCB. During the refresh time for a particular
strobe column, the state of the four keyboard
switches in the column by be read by the
processor. The pn diodes in the strobe lines
prevent simultaneous key closures in different
columns from affecting the display refresh.
Содержание SR620
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Страница 6: ...iv Table of Contents SR620 Universal Time Interval Counter...
Страница 8: ...vi Safety and Preparation for Use SR620 Universal Time Interval Counter...
Страница 12: ...x Specifications SR620 Universal Time Interval Counter...
Страница 58: ...42 Programming Commands SR620 Universal Time Interval Counter...
Страница 72: ...56 Programming Examples SR620 Universal Time Interval Counter...
Страница 76: ...60 Troubleshooting Tips SR620 Universal Time Interval Counter...
Страница 82: ...66 Performance Test SR620 Universal Time Interval Counter...
Страница 90: ...74 Calibration Procedure SR620 Universal Time Interval Counter...
Страница 102: ...86 Circuit Description SR620 Universal Time Interval Counter...
Страница 124: ...108 Parts List SR620 Universal Time Interval Counter...