The 3320 is comprised of the following func-
tional blocks:
Power Supply - Part No. 332950
The power entry assembly interfaces the AC
voltage presented to the instrument with the
power supply. The power supply provides
+15VDC to the main printed circuit board.
The thermoelectric cooling well fan and sole-
noid operate at +15VDC. The secondary cool-
ing fan operates at +12VDC via a drop-down
resistor.
Front End (sample handling assembly)
The sample thermistor measures the tempera-
ture of the sample. The thermoelectric
(whose duty cycle is controlled through the
block probe/thermistor) supercools the sam-
ple. When the supercooled sample reaches a
set temperature (3200 mOsm), the impactor
strikes the sample, causing the sample to
freeze. The main cooling fan remains on as
long as the thermoelectric is running.
The sample handling assembly also includes a
mechanical slide for holding and introducing
the sampler. Under this slide is a microswitch
connected to the application PCB, to automat-
ically start and stop the test routine.
332620 Control Board Set
General: The control board set is made up of
two printed circuit boards in a motherboard/
daughterboard configuration.
PCB120 Processor Board
Processor: The processor used is an Intel
80C186 16-bit embedded processor. The
80C186 contains three programmable 16-bit
timers, two serial ports, programmable inter-
rupts, 1 megabyte of memory address space,
and 64 kilobytes of input/output (I/O) address
space. The processor uses an external 32
MHz crystal to generate the internal 16 MHz
system clock. The processor controls access
to all memory and all I/O.
Memory Map: The 1 megabyte of memory
address space contains read-only memory
(Flash EPROM), read/write memory (static
RAM), and the real time clock. About half of
the address space is unused, allowing for
3320 Circuit Description
Processor
Board
Serial Port
Applications
Board
Cooling
System
Power
Supply
Printer
Port
KeypadDisplay
Barcode
Port
19
The Advanced
®
Osmometer Model 3320 Service Manual
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