EP0494198A1 - Instrumentation amplifier with automatic gain control - Google Patents
Instrumentation amplifier with automatic gain controlInfo
- Publication number
- EP0494198A1 EP0494198A1 EP19900914180 EP90914180A EP0494198A1 EP 0494198 A1 EP0494198 A1 EP 0494198A1 EP 19900914180 EP19900914180 EP 19900914180 EP 90914180 A EP90914180 A EP 90914180A EP 0494198 A1 EP0494198 A1 EP 0494198A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- amplifier
- comparator
- gain
- output voltage
- resistor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 238000005259 measurement Methods 0.000 claims abstract description 9
- 230000003247 decreasing effect Effects 0.000 abstract 1
- 238000010276 construction Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03G—CONTROL OF AMPLIFICATION
- H03G3/00—Gain control in amplifiers or frequency changers
- H03G3/20—Automatic control
- H03G3/30—Automatic control in amplifiers having semiconductor devices
- H03G3/3005—Automatic control in amplifiers having semiconductor devices in amplifiers suitable for low-frequencies, e.g. audio amplifiers
- H03G3/3026—Automatic control in amplifiers having semiconductor devices in amplifiers suitable for low-frequencies, e.g. audio amplifiers the gain being discontinuously variable, e.g. controlled by switching
Definitions
- the present invention relates to an instrumentation ampli- bomb of a type in accordance with the preamble of claim 1.
- An instrumentation amplifier is by definition a device intended for the measurement of analog signals, often at a low level, from different types of sensors.
- the amplifier is conventionally constructed using a few operational ampli ⁇ bombs, but it can also be built around amplifying stages designed around UJT and FET devices .
- the output signal of the instrumentation amplifier is generally read via an analog-to-digital converter connected to a computer that can convert an output signal range 0...5 V of the amplifier into a corresponding digital signal with a scale of 0...1023.
- the measurement signal level can vary widely, e.g., from 10 millivolts to 5 volts which means a span of three orders of magnitude.
- the analog-to-digital converter connected to the computer has a measurement range of 0...5 V
- the lower end of the measurement range has insufficient measurement resolution.
- the converter of the exemplifying case with a resolution of 1:1000 is already insufficient for measurement of millivolt-level signals at any accuracy, although the inherent resolution limit of most analog signals is in the order of 0.1 percent.
- the practical solution to the problem is the so-called logarithmic amplifier, whose.output signal corresponds logarithmically to the input signal.
- a drawback to this approach is that the logarithmic amplifier must be implemented using a forward-biased diode, which is a most temperature-sensitive component.
- the thermal drift of the amplifier must be compensated in one way or another with the help of, e.g., a temperature-dependent resistor also called a thermistor.
- a temperature-dependent resistor also called a thermistor.
- the practical implementations of a logarithmic amplifier tend to be complicated and costly. The feasibility of applications requiring a multitude of sensors can thus easily be limited by cost factors.
- Figure 1 shows the operating principle and a possible practical implementation of the amplifier at the component level.
- the instrumentation ampli ⁇ bomb shown in Fig. 1 is implemented by a design which makes the amplifier to perform an automatic gain control until its output signal is always in a range of, e.g., 1...10 V.
- the amplifier is capable of measuring a voltage span extending from, e.g., one millivolt to ten volts practically at the same accuracy.
- the amplifier can be constructed using simple basic components, which avoids the large thermal drift so difficult to compensate in a logarithmic amplifier.
- the amplifier 1 is provided with a feedback network comprising a multiplexer 2 and resistors 3 so that one resistor at a time is connected from the amplifier output to the input.
- the multiplexer is controlled via control lines 4.
- the control lines are driven by an up/down counter 5.
- the output voltage of the amplifier is compared against a 1 V reference voltage with the help of a comparator 6. If the output voltage is below 1 V, the comparator output goes to logic 1 state and the counter is incremented.
- the output lines 4 of the counter 5 control the multiplexer 2 making it change its channel, whereby a feedback resistor 3 of larger value is selected. Due to the heavy feedback, the output of the amplifier is always held above 1 V.
- the gain of the amplifier can be read by a computer from the states of the output lines of the counter 5.
Landscapes
- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Amplifiers (AREA)
- Indication And Recording Devices For Special Purposes And Tariff Metering Devices (AREA)
- Analogue/Digital Conversion (AREA)
- Control Of Amplification And Gain Control (AREA)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FI894591A FI87861C (fi) | 1989-09-28 | 1989-09-28 | En automatiskt sin foerstaerkning reglerande instrumenteringsfoerstaerkare |
FI894591 | 1989-09-28 |
Publications (1)
Publication Number | Publication Date |
---|---|
EP0494198A1 true EP0494198A1 (en) | 1992-07-15 |
Family
ID=8529071
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19900914180 Withdrawn EP0494198A1 (en) | 1989-09-28 | 1990-09-26 | Instrumentation amplifier with automatic gain control |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP0494198A1 (fi) |
JP (1) | JPH05500590A (fi) |
CA (1) | CA2066705A1 (fi) |
FI (1) | FI87861C (fi) |
WO (1) | WO1991005406A1 (fi) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5886017A (en) * | 1986-06-11 | 1999-03-23 | Procyon Pharmaceuticals, Inc. | Protein kinase C modulators. E. |
FR2702581B1 (fr) * | 1993-03-12 | 1995-06-02 | Sagem | Circuit multiplicateur à potentiomètres et compteur d'énergie électrique incorporant un tel circuit. |
DE102019113360A1 (de) * | 2019-05-20 | 2020-11-26 | Carl Zeiss Microscopy Gmbh | Beleuchtungsvorrichtung für ein Lichtmikroskop und Beleuchtungsverfahren |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2853642A1 (de) * | 1978-12-09 | 1980-06-12 | Biotronik Mess & Therapieg | Amplituden-regeleinrichtung fuer ekg-signale |
US4739307A (en) * | 1984-01-31 | 1988-04-19 | Analogic Corporation | Multichannel predictive gain amplifier system |
US4553104A (en) * | 1984-03-01 | 1985-11-12 | Honeywell Inc. | Method of compensating an amplifier system having a variable gain amplifier to achieve a constant overall system signal gain and an apparatus utilizing the same |
FR2592537B1 (fr) * | 1985-12-30 | 1991-05-31 | Inst Francais Du Petrole | Dispositif pour l'amplification et l'echantillonnage de signaux analogiques multiplexes. |
-
1989
- 1989-09-28 FI FI894591A patent/FI87861C/fi not_active IP Right Cessation
-
1990
- 1990-09-26 WO PCT/FI1990/000226 patent/WO1991005406A1/en not_active Application Discontinuation
- 1990-09-26 JP JP51327790A patent/JPH05500590A/ja active Pending
- 1990-09-26 EP EP19900914180 patent/EP0494198A1/en not_active Withdrawn
- 1990-09-26 CA CA 2066705 patent/CA2066705A1/en not_active Abandoned
Non-Patent Citations (1)
Title |
---|
See references of WO9105406A1 * |
Also Published As
Publication number | Publication date |
---|---|
FI87861C (fi) | 1993-02-25 |
CA2066705A1 (en) | 1991-03-29 |
FI87861B (fi) | 1992-11-13 |
FI894591A0 (fi) | 1989-09-28 |
JPH05500590A (ja) | 1993-02-04 |
FI894591A (fi) | 1991-03-29 |
WO1991005406A1 (en) | 1991-04-18 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
17P | Request for examination filed |
Effective date: 19920325 |
|
AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): AT BE CH DE DK ES FR GB IT LI NL SE |
|
RIN1 | Information on inventor provided before grant (corrected) |
Inventor name: PUUMALAINEN, PERTTI Inventor name: OLKKONEN, HANNU |
|
17Q | First examination report despatched |
Effective date: 19950606 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN |
|
R18D | Application deemed to be withdrawn (corrected) |
Effective date: 19970401 |
|
R18D | Application deemed to be withdrawn (corrected) |
Effective date: 19970402 |