FB Physikalische Technik Prof. Dr. Thomas Rose Prof. Dr. Rose FH Münster Stegerwaldstr. 39 48565 Steinfurt Tel: 02551/962 -124 / -166 Fax: 02551/962-201 e-mail: [email protected]20.11.2018 Praktikum Sensortechnik Versuchsbeschreibungen und Testatliste Name: Vorname: Studiengang: Physikalische Technik [ ] Wirtschaftsing. [ ] Matrikelnummer: durchgeführt im: WS Versuch Endtestat Datum Endtestat Unterschrift 1 PSD 2 Temperatur 3 Die / der Studierende hat das Praktikum erfolgreich absolviert und ist zur Klausur Sensortechnik zugelassen Steinfurt, den ___________________________________ Prof. Dr. Thomas Rose Bringen Sie zum Unterschreiben dieses Original und zwei Kopien mit. Das Original ist für Sie, die Kopien für das Dekanat und mich.
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FB Physikalische Technik
Prof. Dr. Thomas Rose
Prof. Dr. Rose FH Münster Stegerwaldstr. 39 48565 Steinfurt Tel: 02551/962 -124 / -166 Fax: 02551/962-201 e-mail: [email protected] 20.11.2018
Zur Entfernungs- und Abstandsmessung werden unter anderem Laser-Triangulationssensor benutzt. Diese senden einen Lichtstrahl, meist einen Laserstrahl, aus. Trifft er auf ein Objekt, wird der Auftreffpunkt über eine Optik auf einen Detektor abgebildet, der nicht nur die Lichtintensität messen kann, sondern auch den Auftreffpunkt. Als Detektor kann eine CCD-Zeile oder eine Positionsempfindliche Diode (PSD) benutzt werden.
Aus dem Auftreffpunkt auf dem Sensor kann dann der Abstand des Objektes berechnet werden. Ihre Aufgabe ist es nun, für einen solchen PSD eine Auswerte-Elektronik aufzubauen und dann zu testen.
DESCRIPTIONThe INA121 is a FET-input, low power instrumenta-tion amplifier offering excellent accuracy. Its versatilethree-op amp design and very small size make it idealfor a variety of general purpose applications. Low biascurrent (±4pA) allows use with high impedancesources.
Gain can be set from 1V to 10,000V/V with a singleexternal resistor. Internal input protection can with-stand up to ±40V without damage.
The INA121 is laser-trimmed for very low offsetvoltage (±200μV), low offset drift (±2μV/°C), andhigh common-mode rejection (106dB at G = 100). Itoperates on power supplies as low as ±2.25V (+4.5V),allowing use in battery operated and single 5V sys-tems. Quiescent current is only 450μA.
Package options include 8-pin plastic DIP and SO-8surface mount. All are specified for the –40°C to+85°C industrial temperature range.
This integrated circuit can be damaged by ESD. Burr-Brownrecommends that all integrated circuits be handled withappropriate precautions. Failure to observe proper handlingand installation procedures can cause damage.
ESD damage can range from subtle performance degradationto complete device failure. Precision integrated circuits maybe more susceptible to damage because very small parametricchanges could cause the device not to meet its publishedspecifications.
Supply Voltage .................................................................................. ±18VAnalog Input Voltage Range ............................................................. ±40VOutput Short-Circuit (to ground) .............................................. ContinuousOperating Temperature ................................................. –55°C to +125°CStorage Temperature ..................................................... –55°C to +125°CJunction Temperature .................................................................... +150°CLead Temperature (soldering, 10s) ............................................... +300°C
NOTE: (1) Stresses above these ratings may cause permanent damage.Exposure to absolute maximum conditions for extended periods may degradedevice reliability.
ABSOLUTE MAXIMUM RATINGS(1)
The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumesno responsibility for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject to changewithout notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrantany BURR-BROWN product for use in life support devices and/or systems.
Top View 8-Pin DIP and SO-8
RG
V–IN
V+IN
V–
RG
V+
VO
Ref
1
2
3
4
8
7
6
5
Top View
PACKAGE SPECIFIEDDRAWING TEMPERATURE PACKAGE ORDERING TRANSPORT
PRODUCT PACKAGE NUMBER(1) RANGE MARKING NUMBER(2) MEDIA
SingleINA121P 8-Pin DIP 006 –40°C to +85°C INA121P INA121P RailsINA121PA 8-Pin DIP 006 –40°C to +85°C INA121PA INA121PA RailsINA121U SO-8 Surface-Mount 182 –40°C to +85°C INA121U INA121U Rails
" " " " " INA121U/2K5 Tape and ReelINA121UA SO-8 Surface-Mount 182 –40°C to +85°C INA121UA INA121UA Rails
" " " " " INA121UA/2K5 Tape and Reel
NOTES: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. (2) Models with a slash (/) areavailable only in Tape and Reel in the quantities indicated (e.g., /2K5 indicates 2500 devices per reel). Ordering 2500 pieces of “INA121U/2K5” will get a single2500-piece Tape and Reel. For detailed Tape and Reel mechanical information, refer to Appendix B of Burr-Brown IC Data Book.
PACKAGE/ORDERING INFORMATION
4®
INA121
TYPICAL PERFORMANCE CURVESAt TA = +25°C, VS = ±15V, unless otherwise noted.
NEGATIVE POWER SUPPLY REJECTIONvs FREQUENCY
Frequency (Hz)
Pow
er S
uppl
y R
ejec
tion
(dB
)
10 100 10k 100k 1M1k
120
100
80
60
40
20
0
G = 1000V/V
G = 1V/V
G = 10V/V
G = 100V/V
INPUT COMMON-MODE RANGEvs OUTPUT VOLTAGE, VS = ±15V
Output Voltage (V)
Com
mon
-Mod
e V
olta
ge (
V)
–15 –10 0 5 15–5
15
10
5
0
–5
–10
–1510
VD/2+
–+
–+VCM
VO
VD/2 Ref
–15V
+15V
G = 1G ≥ 10
POSITIVE POWER SUPPLY REJECTIONvs FREQUENCY
Frequency (Hz)
Pow
er S
uppl
y R
ejec
tion
(dB
)
10 100 10k 100k 1M1k
120
100
80
60
40
20
0
G = 1000V/V
G = 1V/V
G = 10V/V
G = 100V/V
COMMON-MODE REJECTIONvs FREQUENCY
Frequency (Hz)
Com
mon
-Mod
e R
ejec
tion
(dB
)
10 100 10k 100k 1M1k
120
100
80
60
40
20
0
G = 1000V/V
G = 1V/V
G = 10V/V
G = 100V/V
INPUT COMMON-MODE RANGEvs OUTPUT VOLTAGE, VS = ±5V, ±2.5V
Output Voltage (V)
Com
mon
-Mod
e V
olta
ge (
V)
–5
5
4
3
2
1
0
–1
–2
–3
–4
–5–4 –3 –2 –1 0 1 2 3 4 5
VS = ±5VVS = ±2.5V
G = 1
G ≥ 10
G = 1
G ≥ 10
GAIN vs FREQUENCY
Frequency (Hz)
Gai
n (d
B)
1k 10k 1M 10M100k
60
50
40
30
20
10
0
–10
–20
G = 1000V/V
G = 100V/V
G = 10V/V
G = 1V/V
5®
INA121
INPUT BIAS CURRENT vs TEMPERATURE
Temperature (°C)
Bia
s C
urre
nt (
pA)
10k
1k
100
10
1
0.1
0.01–75 –50 –25 0 25 50 75 100 125
IB
IOS
TYPICAL PERFORMANCE CURVES (CONT)At TA = +25°C, VS = ±15V, unless otherwise noted.
INPUT OVER-VOLTAGE V/I CHARACTERISTICS1
0.8
0.6
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
–1
Inpu
t Cur
rent
(m
A)
Input Voltage (V)
–50 –40 –30 –20 –10 10 20 30 400 50
G = 1V/V
G = 1000V/V
G = 1V/VFlat region representsnormal linear operation.
VINIIN –15V
+15V
G = 1000V/V
QUIESCENT CURRENT AND SLEW RATEvs TEMPERATURE
500
475
450
425
400
375–75 –50 –25 0 25 50 75 100 125
Temperature (°C)
Qui
esce
nt C
urre
nt (
μA
)
1.4
1.2
1
0.8
0.6
0.4
Sle
w R
ate
(V/μ
s)
SR
IQ
SHORT-CIRCUIT CURRENTvs TEMPERATURE
±15
±14
±13
±12
±11
±10–75 –50 –25 0 25 50 75 100 125
Temperature (°C)
Sho
rt-C
ircui
t Cur
rent
(μ
A)
+ISC
–ISC
SETTLING TIME vs GAIN1000
100
101 10 100 1000
Gain (V/V)
Set
tling
Tim
e (μ
s)
0.01%
0.1%
INPUT BIAS CURRENTvs COMMON-MODE INPUT VOLTAGE
1m
100μ
10μ
10p
1p
–10μ
–100μ
–1m–20 –15 –10 –5 0 5 10 15 20
Common-Mode Voltage (V)
Inpu
t Bia
s C
urre
nt (
A)
6®
INA121
TYPICAL PERFORMANCE CURVES (CONT)At TA = +25°C, VS = ±15V, unless otherwise noted.
TYPICAL PERFORMANCE CURVES (CONT)At TA = +25°C, VS = ±15V, unless otherwise noted.
SMALL-SIGNAL STEP RESPONSE(G = 100, 1000)
LARGE-SIGNAL STEP RESPONSE(G = 1, 10)
LARGE-SIGNAL STEP RESPONSE(G = 100, 1000)
10μs/div
G = 10
50mV/div
G = 1
100μs/div
G = 100
50mV/div
G = 1000
100μs/div
G = 10
5V/div
G = 1
G = 1000
5V/div
G = 100
100μs/div
8®
INA121
APPLICATION INFORMATIONFigure 1 shows the basic connections required for operationof the INA121. Applications with noisy or high impedancepower supplies may require decoupling capacitors close tothe device pins as shown.
The output is referred to the output reference (Ref) terminalwhich is normally grounded. This must be a low-impedanceconnection to assure good common-mode rejection. A resis-tance of 8Ω in series with the Ref pin will cause a typicaldevice to degrade to approximately 80dB CMR (G = 1).
SETTING THE GAIN
Gain of the INA121 is set by connecting a single externalresistor, RG, connected between pins 1 and 8:
Commonly used gains and resistor values are shown inFigure 1.
(1)G = 1 + 50kΩ
RG
The 50kΩ term in Equation 1 comes from the sum of the twointernal feedback resistors of A1 and A2. These on-chipmetal film resistors are laser trimmed to accurate absolutevalues. The accuracy and temperature coefficient of theseresistors are included in the gain accuracy and drift specifi-cations of the INA121.
The stability and temperature drift of the external gainsetting resistor, RG, also affects gain. RG’s contribution togain accuracy and drift can be directly inferred from the gainequation (1). Low resistor values required for high gain canmake wiring resistance important. Sockets add to the wiringresistance which will contribute additional gain error (possi-bly an unstable gain error) in gains of approximately 100 orgreater.
DYNAMIC PERFORMANCE
The typical performance curve “Gain vs Frequency” showsthat, despite its low quiescent current, the INA121 achieveswide bandwidth, even at high gain. This is due to thecurrent-feedback topology of the INA121. Settling time alsoremains excellent at high gain.
The INA121 provides excellent rejection of high frequencycommon-mode signals. The typical performance curve,“Common-Mode Rejection vs Frequency” shows this be-havior. If the inputs are not properly balanced, however,common-mode signals can be converted to differential sig-nals. Run the VIN and VIN connections directly adjacent eachother, from the source signal all the way to the input pins. Ifpossible use a ground plane under both input traces. Avoidrunning other potentially noisy lines near the inputs.
NOISE AND ACCURACY PERFORMANCE
The INA121’s FET input circuitry provides low input biascurrent and high speed. It achieves lower noise and higheraccuracy with high impedance sources. With source imped-ances of 2kΩ to 50kΩ the INA114, INA128, or INA129 mayprovide lower offset voltage and drift. For very low sourceimpedance (≤1kΩ), the INA103 may provide improvedaccuracy and lower noise. At very high source impedances(> 1MΩ) the INA116 is recommended.
OFFSET TRIMMING
The INA121 is laser trimmed for low offset voltage anddrift. Most applications require no external offset adjust-ment. Figure 2 shows an optional circuit for trimming theoutput offset voltage. The voltage applied to Ref terminal issummed at the output. The op amp buffer provides lowimpedance at the Ref terminal to preserve good common-mode rejection. Trim circuits with higher source impedanceshould be buffered with an op amp follower circuit to assurelow impedance on the Ref pin.
Input circuitry must provide a path for this input bias currentif the INA121 is to operate properly. Figure 3 shows variousprovisions for an input bias current path. Without a biascurrent return path, the inputs will float to a potential whichexceeds the common-mode range of the INA121 and theinput amplifiers will saturate.
If the differential source resistance is low, the bias currentreturn path can be connected to one input (see the thermo-couple example in Figure 3). With higher source impedance,using two resistors provides a balanced input with possibleadvantages of lower input offset voltage due to bias currentand better high-frequency common-mode rejection.
+ –
INPUT BIAS CURRENT RETURN PATH
The input impedance of the INA121 is extremely high—approximately 1012Ω. However, a path must be provided forthe input bias current of both inputs. This input bias currentis typically 4pA. High input impedance means that this inputbias current changes very little with varying input voltage.
INA121
VIN
VIN
RG
–
+
10kΩ(1)
VO
OPA277
Ref
±10mVAdjustment Range
100Ω(1)
100Ω(1)
100μA1/2 REF200
100μA1/2 REF200
V+
V–
NOTE: (1) For wider trim range requiredin high gains, scale resistor values larger
INPUT COMMON-MODE RANGE
The linear input voltage range of the input circuitry of theINA121 is from approximately 1.2V below the positivesupply voltage to 2.1V above the negative supply. A differ-ential input voltage causes the output voltage to increase.The linear input range, however, will be limited by theoutput voltage swing of amplifiers A1 and A2. So the linearcommon-mode input range is related to the output voltage ofthe complete amplifier. This behavior also depends on sup-ply voltage—see typical performance curve “Input Com-mon-Mode Range vs Output Voltage”.
FIGURE 3. Providing an Input Common-Mode Current Path.
FIGURE 2. Optional Trimming of Output Offset Voltage.
10®
INA121
INA121RG
100Ω
VO
+10V
BridgeG = 500
Ref
A1
A2
A3
40kΩ40kΩ
40kΩ40kΩ
RG
V+
V–
INA121
VO = G • VD
G = 1 + 50kΩRG25kΩ
25kΩ
VCM –G • VD
2
VD 2
VD 2
VCM
VCM + G • VD
2
A combination of common-mode and differential inputvoltage can cause the output of A1 or A2 to saturate. Figure4 shows the output voltage swing of A1 and A2 expressed interms of a common-mode and differential input voltages.For applications where input common-mode range must bemaximized, limit the output voltage swing by connecting theINA121 in a lower gain (see performance curve “InputCommon-Mode Voltage Range vs Output Voltage”). Ifnecessary, add gain after the INA121 to increase the voltageswing.
Input-overload can produce an output voltage that appearsnormal. For example, if an input overload condition drivesboth input amplifiers to their positive output swing limit, thedifference voltage measured by the output amplifier will benear zero. The output of A3 will be near 0V even though bothinputs are overloaded.
LOW VOLTAGE OPERATION
The INA121 can be operated on power supplies as low as±2.25V. Performance remains excellent with power suppliesranging from ±2.25V to ±18V. Most parameters vary onlyslightly throughout this supply voltage range—see typical
performance curves. Operation at very low supply voltagerequires careful attention to assure that the input voltagesremain within their linear range. Voltage swing requirementsof internal nodes limit the input common-mode range with lowpower supply voltage. Typical performance curves, “InputCommon-Mode Range vs Output Voltage” show the range oflinear operation for ±15V, ±5V, and ±2.5V supplies.
INPUT FILTERING
The INA121’s FET input allows use of an R/C input filterwithout creating large offsets due to input bias current.Figure 5 shows proper implementation of this input filter topreserve the INA121’s excellent high frequency common-mode rejection. Mismatch of the common-mode input timeconstant (R1C1 and R2C 2), either from stray capacitance ormismatched values, causes a high frequency common-modesignal to be converted to a differential signal. This degradescommon-mode rejection. The differential input capacitor,C3, reduces the bandwidth and mitigates the effects ofmismatch in C1 and C 2. Make C3 much larger than C1 andC 2. If properly matched, C1 and C2 also improve ac CMR.
FIGURE 10. Voltage Controlled Current Source.FIGURE 9. AC-Coupled Instrumentation Amplifier.
INA121
C1
C2
R1 R2
VO
2πR1C1
1fc =
NOTE: To preserve good low frequency CMR,make R1 = R2 and C1 = C2.
RG
Ref
FIGURE 11. Capacitive Bridge Transducer Circuit.
12®
INA121
INA121RG/2
RG = 5.6kΩ
VOLA
RL
RA
10kΩ
Ref
NOTE: Due to the INA121’s current-feedbacktopology, VG is approximately 0.7V less thanthe common-mode input voltage. This DC offsetin this guard potential is satisfactory for manyguarding applications.
Low bias currentallows use with highelectrode impedances.
G = 10
2.8kΩ
VGVG
2.8kΩ
1/2OPA2131
390kΩ
390kΩ
1/2OPA2131
FIGURE 12. Multiplexed-Input Data Acquisition System.
FIGURE 13. Shield Driver Circuit.
INA121VIN
–
VIN+
OPA130
511Ω22.1kΩ22.1kΩ
Ref
VO
For G = 100RG = 511Ω // 2(22.1kΩ)effective RG = 505Ω
100Ω
NOTE: Driving the shield minimizes CMR degradationdue to unequally distributed capacitance on the inputline. The shield is driven at approximately 1V belowthe common-mode input voltage.