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Current Monitors / Sensors/ Detectors Circuits
Sensors / Detectors -- Main Page

Current Monitors / Sensors/ Detectors:  #'s - B      C - G      H - K      L - R     S - Z

 

Last Updated: December 31, 2017 06:39 AM

Circuits Designed by Dave Johnson, P.E. :

AC Current Indicator Light -  This circuit could be wired into a 120vac power line, which feeds power to any load, ranging from 40 watts to 250 watts.  it will turn on a LED light whenever current is being drawn by a load.  it is especially useful for remote lights, where you may not . . . Hobby Circuit designed by Dave Johnson P.E.-October, 2005

AC Current Monitor -  This circuit uses a small AC current transformer from Magnetek to produce an isolated voltage proportional to the AC current in the primary winding.  The transformer contains a single turn primary with a low 0.001-ohm resistance.  it can easily handle 30 . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

AC Indicator-Self Powered -  Often there is a need to monitor when AC current flows into a load.  The circuit below works well for this application.  it uses an off-the-shelf torrid type AC-1020 current transformer from Triad, available from Mouser.  A wire carrying the AC current is . . . Hobby Circuit designed by David A. Johnson P.E.-December, 2007

Bad Light Bulb Indicator -  This request came from a Discover Circuits visitor.  He wanted to turn on a LED indicator light whenever a circuit detected a burned out tail/brake light on a car or truck.  The circuit shown below uses a transistor switch, to detect current flowing through a low value resistor. . . Circuit by David A. Johnson P.E.-December, 2006

Capacitance Proximity Switch
Draws very low power - Ideal for battery-powered applications
6 Models Available - Call 806-368-7747




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

12.5W PWM Heat Source -  The LT2940 measures a high side current and a differential voltage, multiplies them and outputs a current proportional to instantaneous power.  Bidirectional high side currents and bipolar voltage differences are correctly handled by the four-quadrant multiplier and push-pull output stage, which allows the LT2940 to indicate __ Linear Technology/Analog Devices App Note, Apr 26th 2010

120W Supply Monitor Includes ICC of LT2940 -  The LT2940 measures a high side current and a differential voltage, multiplies them and outputs a current proportional to instantaneous power.  Bidirectional high side currents and bipolar voltage differences are correctly handled by the four-quadrant multiplier and push-pull output stage, which allows the LT2940 to indicate__ Linear Technology/Analog Devices App Note, Apr 26th 2010

16-Bit Resolution Unidirectional Current Sense into LTC2433 ADC -  The LTC2433-1 can accurately digitize signal with source impedances up to 5kΩ.  This LTC6101 current sense circuit uses a 4.99kΩ output resistance to meet this requirement, thus no additional buffering is necessary.  __ Linear Technology/Analog Devices App Note, Mar 31, 2010

1-Cell Monitor with Bottom-Side Sense -  The LT2940 measures a high side current and a differential voltage, multiplies them and outputs a current proportional to instantaneous power.  Bidirectional high side currents and bipolar voltage differences are correctly handled by the four-quadrant multiplier and push-pull output stage, which allows the LT2940 to indicate__ Linear Technology/Analog Devices App Note, Apr 26th 2010

2 Sensors Measure Three Line Current -  09/01/95 EDN Design Ideas:  An old technique updated for modern requirements allows you to measure all three line currents in a three-phase system.  You perform this measurement using two current transformers (CTs) and three ammeters.  The original technique appeared in Alternating-Current Machines by George Mueller (McGraw-Hill, 1952).  The method works equally well with modern current sensors.  Figs 1 and 2 illustrate the technique.    __ Circuit Design by Henno Normet, Tavares, FL

28V Power to Frequency Converter -  The LT2940 measures a high side current and a differential voltage, multiplies them and outputs a current proportional to instantaneous power.  Bidirectional high side currents and bipolar voltage differences are correctly handled by the four-quadrant multiplier and push-pull output stage, which allows the LT2940 to indicate__ Linear Technology/Analog Devices App Note, Apr 26th 2010

3.3V/10mA Regulator from a 4mA to 20mA Loop -  This circuit is a 3.3 V/10mA regulator that extracts its power from a 4mA to 20mA loop.  This circuit demonstrates how an LTC1474/LTC1475-based regulator is easily optimized for such low current applications.  The 2W sense resistor limits the peak inductor current to 40mA to minimize current ripple and provide good efficiency __ Linear Technology/Analog Devices App Note, Mar 16th 2011

4-20-mA loop needs no external power source -  09/13/01 EDN Design Ideas:  The simple circuit in Figure 1 uses a low-current-drain MAX4073H amplifier to sense the current flowing through a 4- to 20-mA loop.  The circuit senses the current through a 1Ω resistor with a fixed gain of 100 and uses no battery __ Circuit Design by Shyam Tiwari, Sensors Private Ltd, Gwalior, India

4-20mA Loop Transmitter -  Transmission of industry standard 4-20mA current loop signals to values and other actuators is a common requirement.  Resistive line losses and actuator impedances require current transmitters to be able to force a compliance voltage of a least 20V.  Because of this, 5V powered systems usually cannot meet current loop transmitter __ Linear Technology/Analog Devices App Note, Mar 16th 2011

48V Low Side Precision Current Sense -  This amplifier configuration is essentially the complementary implementation to the classic high-side configuration.  The op amp used must support common-mode operation at its lower rail.  A floating shunt-regulated local supply is provided by the Zener diode, and the transistor provides metered current to an output load __ Linear Technology/Analog Devices App Note, Mar 31, 2010

48V Power Monitor with Opto-Isolated Serial Interface -  The LTC4151 is a high side power monitor that operates over a wide voltage range of 7V to 80V.  in default operation mode, the onboard 12-bit ADC continuously measures high side current, input voltage and an external voltage.  Data is reported through the i2C interface when polled by a host.  The LTC4151 can also perform on-demand__ Linear Technology/Analog Devices App Note, Apr 26th 2010

48V Supply Current Monitor with Isolated Output & 105V Survivability -  The HV version of the LTC6101 can operate with a total supply voltage of 105V.  Current flow in high supply voltage rails can be monitored directly or in an isolated fashion as shown in this circuit.  The gain of the circuit and the level of output current from the LTC6101 depends on the particular opto-isolator used.  __ Linear Technology/Analog Devices App Note, Mar 30th 2010

7.4mA DC Supply from 4mA to 20mA Current Loop -  The LTC3255 is a switched-capacitor step-down DC/DC converter that produces a regulated output (2.4V to 12.5V adjustable) from a 4V to 48V input.  in applications where the input voltage exceeds twice the output voltage, 2:1 capacitive charge pumping extends output current capability beyond input supply current limits.  At no __ Linear Technology/Analog Devices App Note, Sep 19th 2013

AC Current Indicator Light -  This circuit could be wired into a 120vac power line, which feeds power to any load, ranging from 40 watts to 250 watts.  it will turn on a LED light whenever current is being drawn by a load.  it is especially useful for remote lights, where you may not . . . Hobby Circuit designed by Dave Johnson P.E.-October, 2005

AC Current Monitor -  This circuit uses a small AC current transformer from Magnetek to produce an isolated voltage proportional to the AC current in the primary winding.  The transformer contains a single turn primary with a low 0.001-ohm resistance.  it can easily handle 30 . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

AC Indicator-Self Powered -  Often there is a need to monitor when AC current flows into a load.  The circuit below works well for this application.  it uses an off-the-shelf torrid type AC-1020 current transformer from Triad, available from Mouser.  A wire carrying the AC current is . . . Hobby Circuit designed by David A. Johnson P.E.-December, 2007

AC Line Current Detector -  This circuit will detect AC line currents of about 250 mA or more without making any electrical connections to the line.  Current is detected by passing one of the AC lines through an inductive pickup (L1) made with a 1 inch diameter U-bolt wound with 800 turns of #30, #35 magnet wire.  The pickup could be made from other iron type rings or __ Designed by Bill Bowden

AC Power & Current Monitor -  The LT2940 measures a high side current and a differential voltage, multiplies them and outputs a current proportional to instantaneous power.  Bidirectional high side currents and bipolar voltage differences are correctly handled by the four-quadrant multiplier and push-pull output stage, which allows the LT2940 to indicate__ Linear Technology/Analog Devices App Note, Apr 26th 2010

AC Power Current Detector with LM1458 -  This circuit will detect power line currents of 250 mA or more without making electrical connections to the line.  Current is detected by passing a line of alternating current through an inductive pickup (L1) as a screen diameter of 1 inch U-bolt__ 

Active-feedback IC serves as current-sensing instrumentation Amplifier -  24-Jul-03 EDN Design Ideas:  High-speed current sensing presents a designer with some significant challenges.  Most techniques for sensing current involve measuring the differential voltage the current produces as it flows through a sense element, such as a resistor or a Hall-effect device.  The differential voltage across the sense element is generally small and is often riding on a common-mode voltage that is considerably __ Circuit Design by Jonathan Pearson, Analog Devices, Wilmington, MA

Adjustable 0W to 10W Load Box with UVLO & Thermal Shutdown -  The LT2940 measures a high side current and a differential voltage, multiplies them and outputs a current proportional to instantaneous power.  Bidirectional high side currents and bipolar voltage differences are correctly handled by the four-quadrant multiplier and push-pull output stage, which allows the LT2940 to indicate__ Linear Technology/Analog Devices App Note, Apr 26th 2010

Analog-Input serves any microcontroller -  20-Dec-01 EDN Design Ideas:  The simple ADC in Figure 1 is perfect for getting analog signals into a purely digital microcontroller.  Using just five surface-mount parts, you can assemble it for less than 50 cents (1000], which is approximately half the cost of a single-chip-ADC approach in the same volume.  Moreover, this design takes only one pin from the microcontroller to operate __ Circuit Design by Steven Hageman, Agilent Technologies, Santa Rosa, CA

Armature Current Monitor for DC Motor Applications -  The LT1999 is a high speed precision current sense amplifier, designed to monitor bidirectional currents over a wide common mode range.  The LT1999 is offered in three gain options: 10V/V, 20V/V, and 50V/V.  The LT1999 senses current via an external resistive shunt and generates an output voltage, indicating both magnitude and__ Linear Technology/Analog Devices App Note, Nov 16th 2010

Avago Tech Note: Isolated current sensing with ∑-∆ optoisolators -  EDN Design Ideas:  06/12/2014    Sigma-delta optocouplers make for accurate isolated sensing, and can trade off speed for ENOB.    __ Circuit Design

Bad Light Bulb Indicator -  This request came from a Discover Circuits visitor.  He wanted to turn on a LED indicator light whenever a circuit detected a burned out tail/brake light on a car or truck.  The circuit shown below uses a transistor switch, to detect current flowing through a low value resistor. . . Circuit by David A. Johnson P.E.-December, 2006

Bias Voltage & Current Senses for Avalanche Photodiodes -  AN92 Avalanche photodiodes, used in laser based fiberoptic systems, require high voltage bias and accurate, wide range current monitoring.  Bias voltage varies from 15V-90V and current ranges from 100nA to 1mA, a 10, 000:1 dynamic range.  This publication presents various 5 volt powered circuits which meet se requirements.  Appended sections detail specific circuit techniques and cover measurement practice.  __ Linear Technology/Analog Devices

Bias-voltage & current-senses make avalanche photodiodes work -  03/06/03  EDN Technical Article: Feeding and reading an avalanche photodiode takes a high degree of circuit sophistication.   __ Circuit Design by Jim Williams, EDN's most revered contributor, passed away in June 2011 after a stroke.  He was 63.

Bidirectional Battery-Current Monitor -  This circuit provides the capability of monitoring current in either direction through the sense resistor.  To allow negative outputs to represent charging current, VEE is connected to a small negative supply.  in single-supply operation (VEE at ground) , the output range may be offset upwards by applying a positive reference __ Linear Technology/Analog Devices App Note, Mar 30th 2010

Bidirectional Current Sense with Separate Charge/Discharge Output -  The LTC6102/LTC6102HV monitor current via the voltage across an external sense resistor (shunt resistor).  internal circuitry converts input voltage to output current, allowing a small sense signal on a large common mode voltage to be translated to a ground-referred signal.  Low DC offset allows the use of very low shunt resistor __ Linear Technology/Analog Devices App Note, Mar 31, 2010

Bidirectional H-Bridge Monitoring with ADC-Friendly Differential Output -  The dual outputs of the LTC6103 can be used individually to provide overload detection, and/or may be taken as a differential pair to provide a bidirectional signal to an analog-to-digital converter (ADC) for example.  Figure 3 shows a typical circuit for a generic H-bridge application.  The power devices may be complementary __ Linear Technology/Analog Devices App Note, Mar 31, 2010

Bidirectional Isolated High-Side Current Sense with 270 V Common-Mode Rejection  -  The input voltage to the AD7170 ADC is converted into an offset binary code at the output of the ADC.  The code is processed in the PC by using the SDP hardware board and LabViEW software.  Figure 5 shows a comparison between the code seen at the output of the ADC recorded by LabViEW and an ideal code calculated based on a perfect system.  __ Analog Devices from the Lab


Current Monitors / Sensors/ Detectors:  #'s - B      C - G      H - K      L - R     S - Z


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