Sensors / Detectors: Capacitance
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Last Updated on:
Thursday, December 07, 2017 02:04 PM |
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Circuits Designed by Dave Johnson, P.E. : |
- Low
Value Capacitance Meter
This circuit was originally designed to measure the
volume of fluid inside a medical syringe. As designed, it produces a
zero to 5 volt output, corresponding to a capacitance change of about 10 picofarads.
With a digital voltmeter, at its output, it can resolve a capacitance change of
0.002 picofarads or 2 femtofarads.
(added 12/04)
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Precision Low Capacitance Meter
This circuit was originally designed to measure the volume of the fluid inside a
10cc syringe. It used two copper foil strips attached to the outside barrel of
the syringe. The fluid between the two copper strips increases the
capacitance. As the fluid volume decreased, the capacitance also decreased.
With the circuit shown below, it is possible to calibrate the circuit, so the
voltage produced is proportional to the fluid volume inside the syringe. With
the values shown, the circuit produces a 5v DC output,...
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Short Range Reflective Object Sensor NEW
Drawing only 30uA from a 3v supply, this circuit will detect a human finger with a
range of about 1 inch. The sensor uses an inexpensive infrared LED and a
matching photo diode.
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Links to electronic circuits, electronic schematics, designs for engineers,
hobbyists, students & inventors:
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Low Value Capacitance Meter - This circuit was originally designed to
measure the volume of fluid inside a medical syringe. As designed, it
produces a zero to 5 volt output, corresponding to a capacitance change of about 10
picofarads. With a digital voltmeter, at its output, it can resolve a
capacitance change of 0.002 picofarads or 2 femtofarads. (added 12/04) ….
[Designed by David A. Johnson] |
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Mains-operated Capacitive Sensor - Easily adjustable, high sensitivity
circuit. Minimum parts counting (added 3/05) |
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[_OLD-ads-dont_upload/OLD I-ADS from web/ad-djandassoc.htm] |
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Measure open circuited cables using a multimeter - 26-Sep-02 Issue of EDN
You can use a multimeter with capacitance-measurement capability to measure the length
of wire or cable to an open circuit. The capacitance of a pair of wires (or a wire to
a shield] is directly proportional to the length of the wire. If you know the
capacitance per foot of wire, then you can calculate how far it is to the open
circuit.... [Design Idea by Ron Duffy, Agilent Technology, Colorado Springs, CO] |
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Measuring Small Changes in Capacitive Sensors - Microchip Application Note
Published 8-Dec-05 (app note added 2/06) |
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Negative Impedance Improves Capacitive Sensors - 03/30/95 EDN-Design
Ideas.... EDN is migrating links. This link is not verified. Search the "title"
EDN for new link. |
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Precision capacitive sensor interface suits miniature instruments -
24-Jul-08 Issue of EDN A pair of one-shots develops a voltage proportional to
the value of a capacitive sensor and transmits these readings via a LVDS interface....
[Design Idea by Jiaqi Shen and Xiaoshu Cai, University of Shanghai for Science and
Technology, Shanghai, China] |
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Precision Low Capacitance Meter - This circuit was originally designed to
measure the volume of the fluid inside a 10cc syringe. It used two copper foil
strips attached to the outside barrel of the syringe. The fluid between the two
copper strips increases the capacitance. As the fluid volume decreased, the
capacitance also decreased. With the circuit shown below, it is possible to
calibrate the circuit, so the voltage produced is proportional to the fluid volume
inside the syringe. With the values shown, the circuit produces a 5v DC
output,.... [Designed by David A. Johnson] |
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RS232C Link Monitors Animal Activity - 11/06/97 EDN-Design Ideas....A common
need in biological experimentation is the ability to unobtrusively monitor the
activity of small caged animals, such as mice, rats, and rabbits, as they move about
their enclosures. This monitoring must be over long periods and around the
clock. The circuit in.... [Design Idea by W Stephen Woodward, University of North
Carolina--Chapel Hill] |
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Short Range Reflective Object Sensor - Drawing only 30uA from a 3v supply,
this circuit will detect a human finger with a range of about 1 inch. The sensor
uses an inexpensive infrared LED and a matching photo diode. …. [Designed by David A.
Johnson] |
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Solve low-frequency cutoff problems in capacitive sensors - 28-Nov-02 Issue
of EDN One of the first problems a capacitive-sensor analog designer must face
is the low-frequency cutoff. Theoretically, you must fulfill just one simple
requirement a sufficiently large input resistance of the preamplifier's first
stage. In practice, however, many problems lurk behind the seemingly straightforward
design rules.... [Design Idea by Julius Foit, Czech Technical University, Prague,
Czech Republic] |
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Stud Sensor Automatic - This thing is a very neat capacitive sensor. For you
europeans, this little gem is used in north america mostly for detecting wooden beams
behind drywall.... [Reverse engineered schematic by Stepan Novotill] |
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Touch Activated Alarm - Not much to tell here as the circuit speaks for
itself. The 555 can be almost any type, they are all pin-compatible. Although some
CMOS types may not have enough power to drive the transistor, in that case use an
ordinary 555. C1's working voltage should be increased to 25V if you decide to go with
a 12V power source. Change the value of C1 for the desired output pulse.... [Tony van
Roon's circuit] |
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Using the AD7142 & a Capacitive Sensor to Develop a Single-Push Digital Shutter Button
- AN-833 Analog Devices Application Notes (app note added 2/06)
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Zetex Variable Capacitance Diodes - Zetec Semiconductors Applications
Notes An introduction to the basic theory, an explanation of the important parameters,
and typical applications are described within this note. An overview is also provided
for the Zetex range of variable capacitance diodes. (app note added 2/06)
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Sensors / Detectors: Capacitance
Sensors
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