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S
A
NC
FC
SHD
ADC ?
DS М P
S
A
NC
FC
SHD
АDC
а
S
A
NC
FC
SHD
CDev
АS
S
A
NC
b
FC
SHD
МP
АDC
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
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Sensor (S)–converts arbitary physical quantity into
electric signal
Adaptor (A)–provides signal amplification to a required
level; expands a dynamic range of input signal; sensor
adjustment and other DCP channel elements according
to the load.
Normalization circuit (NC)– is used as a filter, unwanted
low-frequency and high frequency components are
removed from the signal
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Functional conversion (FC) of analog signal is carried
out in order to implement units in sensor structure to
display definite mathematical operations and improve
its accuracy parameters.
Sample and hold device(SHD) – is used to store analog
signal for a transformation time period of ADC
Analog-to-digital converter (ADC) –transforms analog
signal into a digital code
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
Digital switch (DS) – selects a channel and transmits
data to a microprocessor.
Microprocessor (MP) – on the one hand, it is a complex
program-driven device, on the other hand, it is an
enormous integrated circuit.

Operational amplifier (OA) – is an analog integrated
environment (IE), voltage is formed on its output, this
voltage is equal to a gain difference between two input
voltages .
U2
_
U0
U1
+
Рис. 1.2
U O  K OL U1  U 2 
OA is totally insensitive to any
components of input signals common to
both OA inputs. It is called a commonmode signal and is given by
U1  U 2
U i com  mod  
2
Ideal frequency selective filter– a device or system which has a gaintransfer characteristic between input and output; it is constant in a
certain frequency bandwidth and there is a naught output in a
stopband.
Advantages of an active filter compared with a passive filter :
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Gain. The active filter with a maximum gain-transfer characteristic can
be greater than unity.
Minimal load impact. A gain-transfer characteristic of an active filter is
practically independent of the load the filter works for and a source
that controls the filter.
Non-inductive filters. To design an active filter only resistors and
capacitors are required, inductance is not required. This feature is
particularly important when operating at relatively low frequencies
(<10 Hz), otherwise it would require larger inductance.

Comparator – a circuit that compares two input voltages
Uвх and Uоп; it generates output voltage Uo=Uh, if Uвх
˃Uоп and Uo=Ul if Uвх Uоп, where Uh и Ul - two fixed
voltage levels (high and low).
U вх
U0
U оп
Рис. 1.8

To store changing analog signals for the time of
conversion, switching and other operations in data
collection systems a sample and hold circuit is used
_
_
+
U1
CН
+
Управляющее
Control voltage
напряжение
U0