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Fluid Level
Detectors / Monitors
Last Updated on:
Friday, March 23, 2012 11:17 AM |
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Circuits Designed by Dave Johnson, P.E. : |
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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.
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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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Links to electronic circuits, electronic schematics, designs for engineers,
hobbyists, students & inventors:
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Capacitance Type Liquid Level Monitor - This circuit was originally designed to
monitor the level of liquid natural gas in a tank but it can be used to also measure
almost any liquid..... [Designed by David A. Johnson] |
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Fluid Level Detector - The above circuit uses an AC-sensing signal to eliminate
electrolytic corrosion on the probes. The AC signal is rectified and used to drive
Transistor T1 that drives the relay. The relay is a 12-V type of your choice.
Transistor T1 can also be a TUP…. [Tony van Roon's circuit] |
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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.....
[Designed by David A. Johnson] |
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Plant Moisture Meter - Stick the metal probes into a freshly watered plant and
adjust R5 for a mid-scale meter deflection. The meter will monitor the soil wetness and
the meter will indicate whether it is to moist or to dry. This circuit uses a dual
power supply which could be created by two 9 volt batteries…. [Randy Linscott's circuit] |
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Plant Power - Following a hunch, the author discovered (or re-discovered?) that
all plants carry an electric charge relative to the ground. This charge is more or
less constant regardless of the size of the plant, a kind of "background voltage" in
nature.....(electronic design added 6/07) |
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Plants Watering Watcher - Varying brightness LED signals the necessity to water
a plant. Very Low consumption,3V powered Circuit..... |
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Plants Watering Watcher-2 - IC1D is a CMOS Schmitt trigger oscillator at about
2KHz. It starts and continues to oscillate with a supply down to 1.24V (the lowest output
voltage of my LM317 variable power supply) or less. IC1A is an inverter. IC1B
is a Schmitt trigger NAND gate. Its output is low only when both inputs are at, or higher
than the upper Schmitt trigger threshold voltage. ….(design added 03/08) |
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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...... [Designed by David A. Johnson] |
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Sonarlike method detects fluid level - 19-Jul-01 Issue of EDN Figure 1
illustrates a simple, cost-effective method of measuring the height of fluid in a column
by using ultrasonic waves. Two piezoelectric transducers generate and listen to the
ultrasonic acoustical wave. First, the transmitter piezo element receives stimulation from
a square wave that lasts three or four cycles..... [Design Idea by Robert LeBoeuf and Eric
Masse, National Semiconductor, Salem, NH] |
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