Fluke PM6685 - Block Diagram Description; General

Block Diagram Description
General
The PM6685 Frequency Counter consists of three main units:
–
Front unit
–
Main board unit
–
Rear panel unit
The following options can be added:
–
GPIB interface including analog output (PM9626B)
–
Prescalers 1.3 GHz (PM9621), 3.0 GHz (PM9624)
–
Oven-controlled crystal oscillators (PM9691 or PM9692)
–
Rack mount adapter (PM9622/02)
–
Battery option (PM9623)
The chassis of the counter consists of a front piece molded in alumi
-
num, an aluminum rear panel, and two profiled aluminum rods that
hold the front and rear panels together. This unit can be slid into the
aluminum cover of the instrument.
The front unit contains all functions needed for the user communica
-
tion. It is connected to the main board unit with a flat cable, and the
molded front unit is fixed to the two profiled aluminum rods with
screws.
The main board unit consists of a PCB mounted on two profiled alu
-
minum rods. Most functions, such as the following, are placed on the
main board:
–
Input amplifiers with trigger level circuits
–
Power supply
–
Measurement logic
–
Microcomputer circuitry
Some outputs, such as the trigger levels and probe compensation
view outputs are directly mounted on the main board.
The rear panel unit is of aluminum with a number of mounted con
-
nectors. Most of the connectors are soldered directly to the main
board. The rear panel is fixed to the two profiled aluminum rods with
screws.
4-2 Block Diagram Description