TECHNICAL PART
Sensor
It is the first "entrance" part of measuring chain that is non stop in
observing the physical quantity in a given atmosphere. It is the most
important part in the device because the quality of the whole measuring and
signal depends on quality and features of sensor to provide both accuracy
and precision.
Accurate and stable negative thermal coefficient has 20 Ohm resistance. It's
characteristic by its good long-term stability and also by its miniature
size. Temperature extension: from -30oC to 120oC. Made by: PMEC Sumperk,
Czech Republic
Negative thermal coefficients of temperature are using contingent of resist
and temperature. Their application is influenced by external conditions
(possible humidity, possible quakes, extreme temperature changes) in which
they have good reiteration of measuring. Negative thermal coefficients are
alloys of oxides (Fe2O3 + TiO2, MnO + CoO). Temperature extensions are from
normal -50 oC to 100 oC to extreme -268 oC to 1 000 oC.
Signal Transformer
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It transforms resistance from NTC
(Negative Thermal Coefficient) into the
electrical tension in extension from -5V to +5V. This signal is then
transferred into the measuring channels of AD transformer. Its function in
the software program is to process non-linear characteristic of NTC NR 355
20K U. Our knowledge in constructions of transformers like this is not
perfect so we worked with professors from Slovak Technical University on its
construction. We found accommodating results after few consultations.
Transforming table is also published in the analysis.
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Measuring module transforms signal from signal transformer into required to
sort and value physical quantities that could be more accurately processed
in a further procedure. It is a module of integration transformer that is
communicating by signal line RS 232.
This is proper especially for measuring small signals from NTC
or other similar coefficients. This transformer was chosen because of its
reasonable price and the fact that it is external. It is compatible with
all kinds of computers (from PC 386 higher). Software does not need any
libraries or DLL files. The application is almost entirely universal.
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Technical Data
Communication and laying on by RS 232
Extension: +- 0.5 V or +- 5 V
Distinguishing: +- 18 bits
4 differentiate inputs
accuracy: +- 0.02% on extension +- 0.5 V
transfer time: 65ms
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| PC Cannon 9 pin | AD 232 Cannon 9 pin |
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| 5-GND | 5-GND |
| 3-TxD | 2-RxD |
| 7-RTS | 8-CTS |
| 8-CTS | 7-RTS |
| 4-DTR | 6-DSR |
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