_______________________________________
______________________________________
Instruction Manual MM850099 ed.02a
_________________________________________ 14 ________________________________________
ON
power -ON- key
OFF
power -OFF- key
t
/
s
simulation value cursors (1 L.S.D. step)
STO
memory load keys
STEP
step value setting on ramp simulation
0, 1, 2
IN - OUT memories
SELECT
set-up procedure
AVERAGE
average measurements
IN/OUT
IN-OUT mode selection
LCD±
display contrast adjustment
HOLD
last measured value display hold
%
technical unit selection
mA
electrical unit selection
ENTER
memory load key
SHIFT
key secondary function
FAST
cursor accelerator (L.S.D. x 100)
A "bip" sound indicates that the instrument has received and
acknowledged the operators instruction.
4.3
Input circuit
This input circuit is based on two shunt resistors to convert the current signal to voltage signal.
The voltage signal is converted from analog to digital with a dedicated integrated circuit.
4.4
Microprocessor
The microprocessor handles all the logic functions of the instrument, drives the digital display and
acknowledges all operator instructions.
The heart of the circuit is a single-chip microcomputer (68HC705C8) that utilizes HCMOS technology to
provide the low power characteristics and high noise immunity of CMOS plus the high speed operation of
HMOS.
The above circuit incorporates a watchdog feature to reset normal operation in case of program blocks
caused by external high energy interferences and two serial communication subsystems (SCI and SPI).
4.5
Firmware
The operating system firmware handles all logic instructions to the internal peripheral circuits and
performs the computation of scale factor and square root.
The application system firmware is resident on the non-volatile memory (EEPROM) on the
microprocessor chip.
It is used to store the installation parameters (autocalibration data, programs data, etc.)
4.6
Digital display
The digital display, mounted on an auxiliary board, uses high contrast LCD technology .