PowerPoint PresentationReview of Electrical Sensors and Actuators
Andrew Mason
Biomedical Engineering (instrumentation)
Sensors p.*
Transducers
Transducer
a device that converts a primary form of energy into a corresponding signal with a different energy form
Primary Energy Forms: mechanical, thermal, electromagnetic, optical, chemical, etc.
take form of a sensor or an actuator
Sensor (e.g., thermometer)
acquires information from the “real world”
Actuator (e.g., heater)
real
world
sensor
actuator
intelligent
feedback
system
convert desired parameter into electrically measurable signal
General Electronic Sensor
secondary transducer: converts electrical signal into analog or digital values
Typical Electronic Sensor System
microcontroller
multiple sensors displayed over internet
µC
thermocouple: temperature difference
compass (magnetic): direction
photodiode/phototransistor: photon energy (light)
infrared detectors, proximity/intrusion alarms
chemical senors: O2, CO2, Cl, Nitrates (explosives)
DNA arrays: match DNA sequences
Sensors p.*
Examples
diameter of part under stress (direct)
movement of a microphone diaphragm to quantify liquid movement through the heart (indirect)
Primary Transducer Types
Inductive Sensors
Capacitive Sensors
Piezoelectric Sensors
Secondary Transducers
Wheatstone Bridge
DR/R = DL/L – DA/A + Dr/r
A = p (D/2)2, for circular wire
Poisson’s ratio, m: relates change in diameter D to change in length L
DD/D = - m DL/L
Gage Factor, G, used to compare strain-gate materials
G = DR/R = (1+2m) + Dr/r
DL/L DL/L
dimensional effect
piezoresistive effect
positive temperature coefficients
formed from semiconductor materials, not metals
often composite of a ceramic and a metallic oxide (Mn, Co, Cu or Fe)
typically have negative temperature coefficients
Thermocouples
based on the Seebeck effect: dissimilar metals at diff. temps. signal
Sensors p.*
Sensor operation
small prism-shaped sample of single-crystal undoped GaAs attached to ends of two optical fibers
light energy absorbed by the GaAs crystal depends on temperature
percentage of received vs. transmitted energy is a function of temperature
Can be made small enough for biological implantation
GaAs semiconductor temperature probe
Microaccelerometer
If R1 = R2, Vout-nominal = 0
Vout varies as R3 changes
VCC
high open-loop gain virtual short between + and - inputs
input impedance: ideally infinite: CMOS opamps are close to ideal
output impedance: ideally zero: practical values 20-100
zero output offset: ideally zero: practical value <1mV
gain-bandwidth product (GB): practical values ~MHz
frequency where open-loop gain drops to 1 V/V
Commercial opamps provide many different properties
low noise
Sensors p.*
Overall amplifier
high input impedance suitable for biopotential electrodes with high output impedance
input stage
gain stage
instrumentation amplifier
With 776 op amps, the circuit was found to have a CMRR of 86 dB at 100 Hz and a noise level of 40 mV peak to peak at the output. The frequency response was 0.04 to 150 Hz for ±3 dB and was flat over 4 to 40 Hz. The total gain is 25 (instrument amp) x 32 (non-inverting amp) = 800.
HPF
8-bit to 12-bit common
Digital
synchronous (with clock)
must match baud rate and bit width, transmission protocol, etc.
frequency encoded
µC
“Smart sensor” = sensor with built-in signal processing & communication
e.g., combining a “dumb sensor” and a microcontroller
Data Acquisition Cards (DAQ)
interface through LabVIEW or user-generated code
Communication Links Common for Sensors
asynchronous serial comm.
universal asynchronous receive and transmit (UART)
1 receive line + 1 transmit line. nodes must match baud rate & protocol
RS232 Serial Port on PCs uses UART format (but at +/- 12V)
can buy a chip to convert from UART to RS232
synchronous serial comm.
I2C = Inter Integrated Circuit bus
designed by Philips for comm. inside TVs, used in several commercial sensor systems
IEEE P1451: Sensor Comm. Standard
several different sensor comm. protocols for different applications
Sensors p.*
Sensor Calibration
offset: nominal output ≠ nominal parameter value
nonlinearity: output not linear with parameter changes
cross parameter sensitivity: secondary output variation with, e.g., temperature
Calibration = adjusting output to match parameter
analog signal conditioning
a,b,c = calibration coefficients
can remove with polynomial evaluation
P = a + bV + cT + dVT + e V2, where P=pressure, T=temperature
T1
T2
T3
offset
linear
non-linear
Chart2
-30
-30
-30
-30
-30
-30
-20
-20
-20
-20
-20
-20
-10
-10
-10
-10
-10
-10
0
0
0
0
0
0
10
10
10
10
10
10
20
20
20
20
20
20
30
30
30
30
30
30
40
40
40
40
40
40
50
50
50
50
50
50
60
60
60
60
60
60
70
70
70
70
70
70
1001
1010
1001
1101
1110
1111
1.00E-12
5
2
3.5
0.05
10
2
3.5
T
IDd
0.02
Temp.
0001
0010
0011
1001
1010
1001
1101
1110
1111
-30
0.318
1.010
1.204
0.341
1.283
1.613
-0.102
1.571
2.359
-20
0.424
0.988
1.152
0.471
1.287
1.579
0.098
1.641
2.376
-10
0.502
0.958
1.095
0.579
1.283
1.542
0.281
1.703
2.389
0
0.556
0.921
1.034
0.667
1.273
1.500
0.447
1.759
2.397
10
0.587
0.877
0.970
0.735
1.255
1.454
0.599
1.807
2.402
20
0.600
0.827
0.902
0.788
1.232
1.405
0.736
1.848
2.402
30
0.596
0.771
0.830
0.824
1.202
1.352
0.860
1.883
2.398
40
0.577
0.710
0.756
0.847
1.166
1.295
0.972
1.912
2.390
50
0.545
0.643
0.677
0.857
1.125
1.235
1.071
1.935
2.378
60
0.502
0.571
0.596
0.856
1.079
1.172
1.160
1.953
2.363
70
0.447
0.494
0.512
0.843
1.027
1.106
1.238
1.965
2.344
5
2
3.5
0.1
10
2
3.5
15
2
3.5
-1
5
3
3
0
10
3
3
15
3
3
5
3
8
10
3
8
15
3
8
0001
0010
0011
1001
1010
1001
1101
1110
1111
6.0E-06
2E-06
2E-06
Freq.
1.0E-05
2E-06
2E-06
Freq.
1.5E-05
2E-06
2E-06
Freq.
5E-06
2E-06
3.5E-06
Freq.
1.0E-05
2E-06
3.5E-06
Freq.
1.5E-05
2E-06
3.5E-06
Freq.
5E-06
3E-06
8E-06
Freq.
1.0E-05
3E-06
8E-06
Freq.
1.5E-05
3E-06
8E-06
Freq.
Temp.
IC(T)
ID(T)
IDd(T)
Period
MHz
IC(T)
ID(T)
IDd(T)
Period
MHz
IC(T)
ID(T)
IDd(T)
Period
MHz
IC(T)
ID(T)
IDd(T)
Period
MHz
IC(T)
ID(T)
IDd(T)
Period
MHz
IC(T)
ID(T)
IDd(T)
Period
MHz
IC(T)
ID(T)
IDd(T)
Period
MHz
IC(T)
ID(T)
IDd(T)
Period
MHz
IC(T)
ID(T)
IDd(T)
Period
MHz
-30
5.00E-07
7.50E-06
7.50E-06
-1.9E-08
0.000
4.50E-06
7.50E-06
7.50E-06
-4.0E-07
0.000
9.50E-06
7.50E-06
7.50E-06
1.3E-06
0.789
-5.00E-07
7.50E-06
9.00E-06
-2.8E-08
0.000
4.50E-06
7.50E-06
9.00E-06
-4.4E-07
0.000
9.50E-06
7.50E-06
9.00E-06
1.2E-06
0.818
-5.00E-07
8.50E-06
1.35E-05
-7.4E-08
0.000
4.50E-06
8.50E-06
1.35E-05
-3.5E-07
0.000
9.50E-06
8.50E-06
1.35E-05
2.1E-06
0.466
-20
1.50E-06
6.50E-06
6.50E-06
-9.2E-08
0.000
5.50E-06
6.50E-06
6.50E-06
-1.7E-06
0.000
1.05E-05
6.50E-06
6.50E-06
8.1E-07
1.238
5.00E-07
6.50E-06
8.00E-06
-8.3E-08
0.000
5.50E-06
6.50E-06
8.00E-06
-1.8E-06
0.000
1.05E-05
6.50E-06
8.00E-06
7.5E-07
1.333
5.00E-07
7.50E-06
1.25E-05
-1.3E-07
0.000
5.50E-06
7.50E-06
1.25E-05
-8.4E-07
0.000
1.05E-05
7.50E-06
1.25E-05
8.3E-07
1.210
-10
2.50E-06
5.50E-06
5.50E-06
-3.0E-07
0.000
6.50E-06
5.50E-06
5.50E-06
2.4E-06
0.423
1.15E-05
5.50E-06
5.50E-06
7.0E-07
1.435
1.50E-06
5.50E-06
7.00E-06
-2.1E-07
0.000
6.50E-06
5.50E-06
7.00E-06
2.3E-06
0.438
1.15E-05
5.50E-06
7.00E-06
6.2E-07
1.615
1.50E-06
6.50E-06
1.15E-05
-2.3E-07
0.000
6.50E-06
6.50E-06
1.15E-05
0.02
Temp.
0001
0010
0011
1001
1010
1001
1101
1110
1111
-30
0.318
1.010
1.204
0.341
1.283
1.613
-0.102
1.571
2.359
-20
0.424
0.988
1.152
0.471
1.287
1.579
0.098
1.641
2.376
-10
0.502
0.958
1.095
0.579
1.283
1.542
0.281
1.703
2.389
0
0.556
0.921
1.034
0.667
1.273
1.500
0.447
1.759
2.397
10
0.587
0.877
0.970
0.735
1.255
1.454
0.599
1.807
2.402
20
0.600
0.827
0.902
0.788
1.232
1.405
0.736
1.848
2.402
30
0.596
0.771
0.830
0.824
1.202
1.352
0.860
1.883
2.398
40
0.577
0.710
0.756
0.847
1.166
1.295
0.972
1.912
2.390
50
0.545
0.643
0.677
0.857
1.125
1.235
1.071
1.935
2.378
60
0.502
0.571
0.596
0.856
1.079
1.172
1.160
1.953
2.363
70
0.447
0.494
0.512
0.843
1.027
1.106
1.238
1.965
2.344
5
2
3.5
0.02
10
2
3.5
15
2
3.5
5
3
3
10
3
3
15
3
3
5
3
8
10
3
8
15
3
8
5E-06
2E-06
2E-06
Freq.
1.0E-05
2E-06
2E-06
Freq.
1.5E-05
2E-06
2E-06
Freq.
5E-06
2E-06
3.5E-06
Freq.
1.0E-05
2E-06
3.5E-06
Freq.
1.5E-05
2E-06
3.5E-06
Freq.
5E-06
3E-06
8E-06
Freq.
1.0E-05
3E-06
8E-06
Freq.
1.5E-05
3E-06
8E-06
Freq.
Temp.
IC(T)
ID(T)
IDd(T)
Period
MHz
IC(T)
ID(T)
IDd(T)
Period
MHz
IC(T)
ID(T)
IDd(T)
Period
MHz
IC(T)
ID(T)
IDd(T)
Period
MHz
IC(T)
ID(T)
IDd(T)
Period
MHz
IC(T)
ID(T)
IDd(T)
Period
MHz
IC(T)
ID(T)
IDd(T)
Period
MHz
IC(T)
ID(T)
IDd(T)
Period
MHz
IC(T)
ID(T)
IDd(T)
Period
MHz
-30
3.90E-06
3.10E-06
3.10E-06
3.1E-06
0.318
8.90E-06
3.10E-06
3.10E-06
9.9E-07
1.010
1.39E-05
3.10E-06
3.10E-06
8.3E-07
1.204
3.90E-06
3.10E-06
4.60E-06
2.9E-06
0.341
8.90E-06
3.10E-06
4.60E-06
7.8E-07
1.283
1.39E-05
3.10E-06
4.60E-06
6.2E-07
1.613
3.90E-06
4.10E-06
9.10E-06
-9.8E-06
-0.102
8.90E-06
4.10E-06
9.10E-06
6.4E-07
1.571
1.39E-05
4.10E-06
9.10E-06
4.2E-07
2.359
-20
4.10E-06
2.90E-06
2.90E-06
2.4E-06
0.424
9.10E-06
2.90E-06
2.90E-06
1.0E-06
0.988
1.41E-05
2.90E-06
2.90E-06
8.7E-07
1.152
4.10E-06
2.90E-06
4.40E-06
2.1E-06
0.471
9.10E-06
2.90E-06
4.40E-06
7.8E-07
1.287
1.41E-05
2.90E-06
4.40E-06
6.3E-07
1.579
4.10E-06
3.90E-06
8.90E-06
1.0E-05
0.098
9.10E-06
3.90E-06
8.90E-06
6.1E-07
1.641
1.41E-05
3.90E-06
8.90E-06
4.2E-07
2.376
-10
4.30E-06
2.70E-06
2.70E-06
2.0E-06
0.502
9.30E-06
2.70E-06
2.70E-06
1.0E-06
0.958
1.43E-05
2.70E-06
2.70E-06
9.1E-07
1.095
4.30E-06
2.70E-06
4.20E-06
1.7E-06
0.579
9.30E-06
2.70E-06
4.20E-06
7.8E-07
1.283
1.43E-05
2.70E-06
4.20E-06
6.5E-07
1.542
4.30E-06
3.70E-06
8.70E-06
3.6E-06
0.281
9.30E-06
3.70E-06
8.70E-06
5.9E-07
1.703
1.43E-05
3.70E-06
8.70E-06
4.2E-07
2.389
0
4.50E-06
2.50E-06
2.50E-06
1.8E-06
0.556
9.50E-06
2.50E-06
2.50E-06
1.1E-06
0.921
1.45E-05
2.50E-06
2.50E-06
9.7E-07
1.034
4.50E-06
2.50E-06
4.00E-06
1.5E-06
0.667
9.50E-06
2.50E-06
4.00E-06
7.9E-07
1.273
1.45E-05
2.50E-06
4.00E-06
6.7E-07
1.500
4.50E-06
3.50E-06
8.50E-06
2.2E-06
0.447
9.50E-06
3.50E-06
8.50E-06
5.7E-07
1.759
1.45E-05
3.50E-06
8.50E-06
4.2E-07
2.397
10
4.70E-06
2.30E-06
2.30E-06
1.7E-06
0.587
9.70E-06
2.30E-06
2.30E-06
1.1E-06
0.877
1.47E-05
2.30E-06
2.30E-06
1.0E-06
0.970
4.70E-06
2.30E-06
3.80E-06
1.4E-06
0.735
9.70E-06
2.30E-06
3.80E-06
8.0E-07
1.255
1.47E-05
2.30E-06
3.80E-06
6.9E-07
1.454
4.70E-06
3.30E-06
8.30E-06
1.7E-06
0.599
9.70E-06
3.30E-06
8.30E-06
5.5E-07
1.807
1.47E-05
3.30E-06
8.30E-06
4.2E-07
2.402
20
4.90E-06
2.10E-06
2.10E-06
1.7E-06
0.600
9.90E-06
2.10E-06
2.10E-06
1.2E-06
0.827
1.49E-05
2.10E-06
2.10E-06
1.1E-06
0.902
4.90E-06
2.10E-06
3.60E-06
1.3E-06
0.788
9.90E-06
2.10E-06
3.60E-06
8.1E-07
1.232
1.49E-05
2.10E-06
3.60E-06
7.1E-07
1.405
4.90E-06
3.10E-06
8.10E-06
1.4E-06
0.736
9.90E-06
3.10E-06
8.10E-06
5.4E-07
1.848
1.49E-05
3.10E-06
8.10E-06
4.2E-07
2.402
30
5.10E-06
1.90E-06
1.90E-06
1.7E-06
0.596
1.01E-05
1.90E-06
1.90E-06
1.3E-06
0.771
1.51E-05
1.90E-06
1.90E-06
1.2E-06
0.830
5.10E-06
1.90E-06
3.40E-06
1.2E-06
0.824
1.01E-05
1.90E-06
3.40E-06
8.3E-07
1.202
1.51E-05
1.90E-06
3.40E-06
7.4E-07
1.352
5.10E-06
2.90E-06
7.90E-06
1.2E-06
0.860
1.01E-05
2.90E-06
7.90E-06
5.3E-07
1.883
1.51E-05
2.90E-06
7.90E-06
4.2E-07
2.398
40
5.30E-06
1.70E-06
1.70E-06
1.7E-06
0.577
1.03E-05
1.70E-06
1.70E-06
1.4E-06
0.710
1.53E-05
1.70E-06
1.70E-06
1.3E-06
0.756
5.30E-06
1.70E-06
3.20E-06
1.2E-06
0.847
1.03E-05
1.70E-06
3.20E-06
8.6E-07
1.166
1.53E-05
1.70E-06
3.20E-06
7.7E-07
1.295
5.30E-06
2.70E-06
7.70E-06
1.0E-06
0.972
1.03E-05
2.70E-06
7.70E-06
5.2E-07
1.912
1.53E-05
2.70E-06
7.70E-06
4.2E-07
2.390
50
5.50E-06
1.50E-06
1.50E-06
1.8E-06
0.545
1.05E-05
1.50E-06
1.50E-06
1.6E-06
0.643
1.55E-05
1.50E-06
1.50E-06
1.5E-06
0.677
5.50E-06
1.50E-06
3.00E-06
1.2E-06
0.857
1.05E-05
1.50E-06
3.00E-06
8.9E-07
1.125
1.55E-05
1.50E-06
3.00E-06
8.1E-07
1.235
5.50E-06
2.50E-06
7.50E-06
9.3E-07
1.071
1.05E-05
2.50E-06
7.50E-06
5.2E-07
1.935
1.55E-05
2.50E-06
7.50E-06
4.2E-07
2.378
60
5.70E-06
1.30E-06
1.30E-06
2.0E-06
0.502
1.07E-05
1.30E-06
1.30E-06
1.8E-06
0.571
1.57E-05
1.30E-06
1.30E-06
1.7E-06
0.596
5.70E-06
1.30E-06
2.80E-06
1.2E-06
0.856
1.07E-05
1.30E-06
2.80E-06
9.3E-07
1.079
1.57E-05
1.30E-06
2.80E-06
8.5E-07
1.172
5.70E-06
2.30E-06
7.30E-06
8.6E-07
1.160
1.07E-05
2.30E-06
7.30E-06
5.1E-07
1.953
1.57E-05
2.30E-06
7.30E-06
4.2E-07
2.363
70
5.90E-06
1.10E-06
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2.2E-06
0.447
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Freq.
MHz
Temp.
0001
0010
0011
1001
1010
1001
1101
1110
1111
-30
0.3179487179
1.0101123596
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0.4243902439
0.9879120879
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0.4714285714
1.2867924528
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0.0978021978
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0.5023255814
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1.2833333333
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0.5555555556
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0.4473684211
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0.5872340426
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0.6
0.8272727273
0.9020134228
0.7875
1.2315789474
1.4048780488
0.7363636364
1.8483221477
2.4015075377
30
0.5960784314
0.7712871287
0.8304635762
0.8242424242
1.2017241379
1.3518072289
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2.3975124378
40
0.5773584906
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0.7555555556
0.8470588235
1.1661016949
1.2952380952
0.9718446602
1.9124183007
2.3896551724
50
0.5454545455
0.6428571429
0.6774193548
0.8571428571
1.125
1.2352941176
1.0714285714
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60
0.501754386
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0.5961783439
0.8555555556
1.0786885246
1.1720930233
1.1598130841
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0.4474576271
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1.0274193548
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