Signal Conditioning
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Amplifiers and Filters
Transcript of Signal Conditioning
-
Signal Conditioningmohammad iqbal [email protected]
Teknik Elektro
Universitas Muria Kudus
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2Signal Conditioning
1. Introduction to signal conditioning
2. Bridge circuits
3. Amplifiers
4. Filters
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3Amplifiers
-
4Op amp characteristic
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5Summing amplifier
+= 2
3
21
1
2 VRRV
RRVout
-
6Noninverting amplifier
inout
outinin
VRRV
RVV
RV
II
+=
=
+
=+
1
2
21
21
1
0
0
-
7Exercise 7
Design a high impedance
amplifier with a voltage
gain of 42 if R1 = 1 k is
chosen.
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8Differential amplifier
( )CMRRCMRAACMRR
VVV
cm
bacm
10log20
2
=
=
+=
( )baout VVAV = The transfer function;
Common mode rejection;
( )121
2 VVRRVout =
-
9Voltage-to-Current converter
( )( )
543
354
42531
31
2
RRR
RI
VRRR
RRRRR
VRR
RI
m
sat
ml
in
++
+
=
=+
=
-
10
Current-to-Voltage converter
IRVout =
-
11
Integrator
tRCKV
dtVRC
V
dtdVC
RV
out
inout
outin
=
=
=+
1
0
-
12
Exercise 8
Use an integrator to
produce a linear ramp
voltage rising at 10 V per
ms. Determine the R and C.
-
13
Differentiator
dtdVRCV
RV
dtdVC
inout
outin
=
=+ 0
-
14
Linearization
( )
=
=+
RVGV
VIR
V
inout
outin 0
-
15
Linearization
( ) ( )( ) ( )RIVV
VIVI
eincout
outout
0
0
log1log1exp
=
=
-
16
Filters
-
17
Filters
Filter : a circuit that is designed to pass signals with desired frequencies and reject or attenuate others
4 types of filters:
1. Low-pass filter: passes low frequencies and stops high frequencies
2. High-pass filter: passes high frequencies and rejects low frequencies
3. Band-pass filter: passes frequencies within a frequency band and blocks or attenuates frequencies outside the band
4. Band-reject filter: passes frequencies outside a frequency band and blocks or attenuates frequencies within the band
-
18
Low-pass RC filter
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19
Low-pass RC filter
Critical frequency:
Output-to-input voltage ratio:
RCfc pi2
1=
( )2/11
cin
out
ffVV
+=
-
20
Exercise 9
A measurement signal has a frequency less than
1 kHz, but there is unwanted noise at about 1
MHz. Design a lowpass filter that attenuates the
noise to 1% if a capacitor 0.01 F has been
used. What is the effect on the measurement
signal at its maximum of 1 kHz?
-
21
High-pass RC filter
-
22
High-pass RC filter
Critical frequency:
Output-to-input voltage ratio:
RCfc pi2
1=
( )( )2/1/
c
c
in
out
ffff
VV
+=
-
23
Exercise 10
Pulses for a stepping motor are
being transmitted at 2000 Hz.
Design a highpass filter to reduce
60 Hz noise and reduce the pulses
by no more than 3 dB.
-
24
Design Methods
1. Determine critical frequency, fc
2. Select standard capacitor (F pF)
3. Calculate required resistance (1 k - 1 M)
4. Use nearest resistance standard value to
calculated value
5. Consider tolerance in resistors and capacitors
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25
Practical considerations
1. Very small resistance -> lead to large currents and
loading effects -> avoid large capacitance
(R= k -M, C= F pF)
2. The exact fc is not important, choose R and C of
approximately to the fc
3. Isolation filter input/output with voltage follower
4. Cascade RC filters to improved fc sharpness ->
consider loading
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26
Band-pass RC filter
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27
Band-pass RC filter
Critical frequency:
Output-to-input voltage ratio:
HHL CR
fpi2
1=
( ) ( )[ ]L
H
HLLH
H
in
out
RR
r
ffrffffff
VV
=
+++=
2222 1
LLH CR
fpi2
1=
-
28
Exercise 11
A signal conditioning system uses a frequency
variation from 6 kHz to 60 kHz to carry
measurement information. There is considerable
noise at 120 Hz and at 1 MHz. Design a
bandpass filter to reduce the noise by 90%.
What is the effect on the desired passband
frequencies if r = 0.01? Determine all the
resistors and capacitors.
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29
Band-pass RC filter
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30
Band-reject RC filter
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31
Twin-T notch filter
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32
Twin-T notch filter
Critical frequency:
Grounding resistor and capacitor:
cn ff 785.0= RCfC pi21
=
cH ff 57.4=cL ff 187.0=
101RR pi=
pi
CC 101 =
