Fluid Level Monitors

Fluid Level Detectors / Monitors
Last Updated on: Friday, October 16, 2009 03:41 AM

Circuits Designed by Dave Johnson, P.E. :

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. Two custom insulated metal tubes form a capacitor plate. The capacitance between the two tubes increases as the level of the liquid rises. The circuit converts an increase of capacitance into a positive voltage change. The circuit could be changed to handle almost any scale factor needed.

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.

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,...

Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

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. Two custom insulated metal tubes form a capacitor plate. The capacitance between the two tubes increases as the level of the liquid rises. The circuit converts an increase of capacitance into a positive voltage change. The circuit could be changed to handle almost any scale factor needed. ….(designed by David A. Johnson)

Fluid Level Detector (Tony van Roon) - (schematic / circuit added 10/02)

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. ….(designed by David A. Johnson)

Plant Moisture Meter (Randy Linscott) - 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….(added 05/08)

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)

Plants Watering Watcher - Varying brightness LED signals the necessity to water a plant. Very Low consumption,3V powered Circuit (added 9/04)

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)

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)

Sonarlike Method Detects Fluid Level - 07/19/01 EDN-Design Ideas: 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 added 1/05)