IM 12D7B2-E-H
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2-2. Functional description
The EXA SC200 is a real time micro-control-
ler operated conductivity-analyzing system.
It uses a dedicated micro-controller to con-
trol all function necessary in such a system.
The input and output functions are concen-
trated in the analogue section of the instru-
ment. Even these functions are operated
through special interfaces designed to give
a minimum of interference problems to the
digital functions. A separation of function is
strictly executed.
By using very low power components it is
possible to make a complete micro-compu-
ter system work on less than 4 mA current.
By using an EEPROM for essential informa-
tion the operating parameters are fixed in
memory without the need for batteries. The
supply-voltage is stabilized by regulators to
the internal supply system. Any voltage
between 17 and 40 Volt is acceptable.
The user-interface is limited to a basic set of
6 keys accessible through the flexible win-
dow cover.
The software is designed with the user in
mind. It uses a simple 3 layer set-up to
communicate with the operator by giving
messages on the second line of the display
area and indicating which keys are to be
pressed in the display too.
The keys are scanned continuously and the
actions are taken immediately. An extensive
system of checking values and parameters
is implemented.
The EXA SC200 operates just like a normal
2-wire instrument but with additional func-
tions. These extra functions are possible by
using a micro-controller at the heart of the
system.
- Continuous sensor polarisation checking
during measurement.
- Automatic optimisation of measuring pulse
frequency and reference voltage.
- Accurate temperature compensation by
non liner NaCI algorithm.
- Simple output range adaptation making it
a versatile instrument.
- A HOLD-function for the current output
signal.
- Selection of temperature sensors.
- Passcode protection.
Additionally YOKOGAWA designed the in-
strument in such a way that an intrinsically
safe version is available with the same featu-
res and specifications. In fact the instrument
is only adapted slightly to fulfil the require-
ments of CENELEC.
The instrument comes in 2 versions only:
-A general purpose model.
-An intrinsically safe model.
This makes it easy to set up the instrument
on site and valuable for large scale exchan-
ges or emergency operations.
Summary of Contents for SC200
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