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Tester or Measurement (Instrument) Circuits

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Last Updated: November 22, 2021 02:42 PM
Circuits Designed by Dave Johnson, P.E. :

Scare Off Pigeons -  I have an area on my roof where a large flock of pigeons like to roost.  Their nesting materials and droppings really make a mess.  Often there is enough junk from them that it clogs my roof gutters.  Perhaps one way to scare them away . . . Hobby Circuit designed by David Johnson P.E.-April, 2005

Self Powered AC Indicator -  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 Johnson P.E.-December, 2007

Self-Powered AC Current Indicator -  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. . . Circuit by David Johnson P.E.-December, 2007

Serial Data Bus Status Monitor -  I designed this circuit many years ago and have used it several times since.  it uses a single logic IC to indicate the TXD and RXD line activity of a typical RS-232 serial data communications link.  The thresholds are set at plus 3 volts and minus 3 volt. . . Circuit by David A. Johnson P.E.-December, 2007

Capacitance Proximity Switch
Draws very low power - Ideal for battery-powered applications
6 Models Available - Call 806-778-8407




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

Safely Applies Power to ICs -  11/22/01  EDN Design Ideas:  Supervisory circuits normally monitor a microprocessor's supply voltage, asserting reset to the IC during power-up, power-down, and brownout.  in this way, the circuit ensures that the supply voltage is stable before the microproces Design by Clayton Grantham, National Semiconductor, Tucson, AZ

Safely Deep-discharges NiCd battery  -  04/29/99  EDN-Design ideas –  NOTE:  Scroll to find this circuit.   Also available at - http://m.eet.com/media/1150682/25098-42999dI     Nickel-cadmium (NIC d) batteries can possess an undesirable memory effect due to partial discharges.  The remedy is a complete discharge before charging again. Figure 1a shows a simple circuit that performs this feat.  Design by Jim Hagerman, Science & Technology International, Honolulu, HI

Sailor’s Battery Meter -  On a sailboat, the condition of the battery is a major concern for obvious reasons.  On the author’s boat, a 120 Ah lead-acid battery is charged from a 25 watts solar panel.  The battery monitor described here was designed to give peace of mind.  it consists of two sub circuits: a sensor and a control/readoutmust register on this site __ Designed by Published in Elecktor July/Aug, 2010

Sallen-Key Low Pass Filter Calculator (handles Butterworth filters, Bessel filters & Chebychev) -  This calculator calculates the capacitor values for a Sallen-Key low pass Butterworth, Bessel, and Chebyshev filters.   __  Daycounter Inc

Salt Taster -  This circuit was designed to detect the approximate percentage of salt contained in a liquid.  After careful setting it can be useful to persons needing a quick, rough indication of the salt content in liquid foods for diet purposes etc.  IC 1A op-amp is wired as a DC differential amplifier and its output voltage increases as the DC resistance measured across the probes decreases.  in fact, fresh water has a relatively high DC resistance value that will decrease proportionally as an increasing amount of salt is added.__ Learning Electronics

Salt-Taster -  Detects the amount of salt contained in liquid foods; Three-level LED indicator __ Contact Flavio Dellepiane, fladello @ tin.it

Sample Derivative of a Waveform -  09/14/00 EDN Design Ideas:  Basic derivative (differentiating) circuits use a lowpass filter or an active operational-amplifier implementation.  These circuits need a large-value capacitor when differentiating a slowly varying signal.  Moreover, the circuits  Design by Joaquin Garcia

Sampling peak Detector has shutdown feature -  05/16/02 EDN Design Ideas:  You face a serious problem in using a slow ADC with a fast peak detector.  The circuit in Figure 1 allows a slow ADC to measure a fast, sampled signal peak.  The 100-MHz peak detector for ultrasonic-pulse sampling uses a fast MAX4231 amplifier from Maxim (www.maxim-ic.com].  This amplifier has a shutdown feature that facilitates power savings without losing the sampled information Design by Shyam Tiwari, Sensors Technology Private Ltd, Gwalior, India

Sanyo 20EZ Monitor -  Schematic only, no circuit description included.   __ Contact jrokweb @ san.rr.com

Satellite Finder -  Schematic only __ Designed by va3iul

Scanning Voltmeter with Minimum Mass Wireless Coupler -  ATMega8  A 10 bit scanning voltmeter with a Minimum Mass Wireless Coupler, based on the ATMega8.  Range to the Minimum Mass Base Unit is 10 to 15 cm.  if the voltmeter is battery operated, it can be floated from ground.   __ Designed by Dick Cappels

Scare Off Pigeons -  I have an area on my roof where a large flock of pigeons like to roost.  Their nesting materials and droppings really make a mess.  Often there is enough junk from them that it clogs my roof gutters.  Perhaps one way to scare them away . . . Hobby Circuit designed by David Johnson P.E.-April, 2005

Schematics & C code for a 0-5V PIC LCD volt meter -  This PIC  LCD volt meter project uses a PIC  micro and an HD44870 LCD display.  The analogue input is taken directly to the analogue input pin of the microcontroller without any other processing. __ Designed by John Main

Schematics & C code for a PIC frequency counter operating up to about 50 MHz (LCD) -  This PIC  frequency counter project uses an LCD to display the frequency and PIC  timer 1 to measure the input signal and Timer0 to measure the timing period. __ Designed by John Main

Scheme Detects shorts -  07/08/99  EDN Design Ideas:  NOTE:  File contains multiple circuits.  Scroll to find this one.  When you manually assemble complex boards, it’s common to short-circuit adjacent component or IC pins.  Determining which section of the circuit you have shorted is not too difficult, but finding the precise point where the short exists can be a formidable task, because the short may be under a surface-mount component. Design by Luis Miguel Brugarolas, SIRE, Madrid, Spain

Scheme provides high-side current-sensing for white-LED drivers -  19-Feb-04 EDN Design Ideas:  White LEDs find wide use in backlighting color-LCD screens in most portable devices, such as cellular phones, PDAs, and MP3 players.  Multiple LEDs often connect in series to ensure that the same current flows through every LED.  To forward-bias these LEDs, a voltage of 10 to 16V comes from an inductor-based boost regulator, such as an SP6690 Design by Dimitry Goder, Sipex Corp, San Jose, CA

Schumann Resonance Detector

Scope probe measures high frequencies -  01/18/96 EDN Design Ideas:  Measuring clocks and critical signals accurately is often inconvenient.  Normal 10x probes usually have about 10 pF of input capacitance, which can considerably affect the signal.  FET probes with 1 to 3 pF of input capacitance are expensive and often require an extra power supply or other special setup.  Unless ground leads are short (10 to 20 mm) , these leads introduce considerable distortion to most probes.    Design by Glenn J Keller,  The 3DO Company, Redwood City, CA

SCR Crowbar -  The LTC1696 is a standalone power supply overvoltage monitor and protection device designed to protect a power supply load in the event of an overvoltage fault.  it monitors two adjustable output voltages.  if an overvoltage condition is detected, the output drives either an external SCR crowbar or turns off external back-to-back__ Linear Technology/Analog Devices App Note, Jul 8th 2011

Secondary-Side AC Breaker -  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

Seismometer & structural vibration meter -  05/14/14  EDN Design Ideas:  Use a TI LDC1000 as a sub-micron displacement sensor for vibration measurement and logging in seismic and structural mechanics applications.   Design by Dmitrii Loukianov

Self Oscillating Amplifier for Distortion Testing -  allows the home constructor to make quite accurate measurements, without having to spend a lot of money on a low distortion oscillator __ Designed by Rod Elliott  ESP

Self Powered AC Indicator -  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 Johnson P.E.-December, 2007

Self-Heated Transistor Digitizes Airflow -  13-Mar--96 EDN Design Ideas:  A sensitive and reliable way to measure airflow is to exploit the predictable relationship between airspeed and the heat dissipated by a sensor exposed to the flow while being held at a constant temperature differential above ambient.  The power required to maintain the elevated sensor temperature is proportional to the square root of the airspeed (King's law).  The popular hot-wire anemometer uses this principle, but suffers from the disadvantage of using a relatively fragile airflow sensor, a thin metallic filament Design by Stephen Woodward, University of North Carolina, Chapel Hill, NC

Self-Powered AC Current Indicator -  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. . . Circuit by David Johnson P.E.-December, 2007

Self-powered Fast Battery-Tester -  This circuit runs a fast battery test without the need of power supply or expensive moving-coil voltmeters.  it has two ranges: when SW1 is set as shown in the circuit diagram, the device can test 3V to 15V batteries.  When SW1 is switched to the other position, only 1.5V cells can be tested. __ Contact IQ Technologies

Self-powered Fast Battery-Tester -  Tests 1.5 to 15 Volt cells; Two-LED display, no power supply required __ Contact Flavio Dellepiane, fladello @ tin.it

Sense Automobile High-Side Current with Discrete Components -  09/14/12  EDN Design Ideas:  Use this circuit to convert a current into a voltage for measurement.   Design by Larry Beaty, Beatys Mills, Comer, Georgia

Sense High-Side Current -  03/01/01 EDN Design Ideas:  The accurate, high-side, current-sense circuit does not use a dedicated, isolated supply voltage, as some other schemes do.    Design by Bobell

Sense Milliamps to Kiloamps & Digitize to 12 Bits -  DN227 Design Notes__ Linear Technology/Analog Devices

Sense multiple pushbuttons using only two wires -  09/09/10 EDN Design Ideas:  A single IC produces a code that indicates which button is pressed.    Design by Bernhard Linke, Maxim Integrated Products Inc, Dallas, TX

Sensing Method Increases Thermal-Response Time -  1/04/96 EDN Design Ideas:  Many temperature-sensing applications require a fast thermal-response time.  Dipping a temperature sensor into a fluid on a production line or the protective shutdown of equipment under a runaway thermal condition are two examples.  in general, semiconductor temperature sensors are limited in their response times because of the high thermal mass and low thermal conductivity of plastic packaging.  Temperature settling times of a few minutes for large step changes ([Delta]T>40°C) in ambient temperatures are common.   Design by John McDonald Analog Devices Santa Clara, CA

Sensitive Remote Control Tester -  Here is a handy gadget for testing of infrared (iR) based remote control transmitters used for TVs and VCRs etc.  The IR signals from a remote control transmitter are sensed by the...__ Electronics Projects for You

Sensitive Temperature Switch -  This temperature switch has a high sensitivity and is quite reliable.  Here, in place of a single transistor, a Darlington pair has been used for switching. At normal room temperature germinum diode...__ Electronics Projects for You

Sensitive Vibration Detector -  This vibration detector is realised using readily available, low cost components.  One of its many applications is in a rolling shutter guard for offices and shops.  The detector will sense vibration...__ Electronics Projects for You

Sensor to Display, Built with Thermistor, 12-Bit ADC, 89S52 & LED Display -  This is my student assignment for the class "Designing Microprocessor Based instrumentation".  The board demonstrates the use of 12-bit ADC, writing c program with digital filtering and interface the LED display.  The reading provides 0.1C sensitivity.  The optional input of the ADC is available for exercise with other input signals or sensors.   __ Designed by Wichit Sirichote

Sequential Tilt-Motion Lock -  Here is a project for locking and unlocking with a tilt sensor by tilting it in a defined sequence.  it uses an accelerometer module to detect the tilt motion.  if the...__ Electronics Projects for You

Serial Data Bus Status Monitor -  I designed this circuit many years ago and have used it several times since.  it uses a single logic IC to indicate the TXD and RXD line activity of a typical RS-232 serial data communications link.  The thresholds are set at plus 3 volts and minus 3 volt. . . Circuit by David A. Johnson P.E.-December, 2007

Serial Port Tests Digitals -  25-Jun-09 EDN Design Ideas:  The circuit in Figure 1 uses a MAX232 IC from Maxim to convert RS-232 voltage levels to TTL levels (Reference 1].  A 74HC4051 from Texas instruments lets you select any of four digital inputs and route them to the serial port (Reference 2].  Listing 1 lets you control the RTS (ready-to-send] and DTR (data-terminal-ready] pins in the serial port that selects the signal under test Design by Yury Magda, Cherkassy, Ukraine

Serial port tests digitals -  A PC's serial port provides signal lines that you can use to read voltage levels of digital circuits.  You can use the port to test digital TTL (transistor-to-transistor-logic) -level circuits.  You just need to convert the TTL levels __ Designed by Yury Magda

Serial Voltmeter using the PIC16C71 -  Building a serial voltage meter to measure from 0 to 5 volts DC is actually pretty easy.  Using MeLabs PicBasic, and Microsoft's Visual Basic Version 5 Pro.  You need Visual Basic Pro version because you will have to use Basic's MSComm control.  This control is not available in the Visual Basic 5 "Learning" Edition.  The PIC 16C71 simplifies the task even more by having a built in A/D converter.  Pins 17, 18, 1, 2 are the analog inputs AiN0, AiN1, AiN2, AiN3 respectively.  __ 

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Got Designs?
Please eMail
if you want me to link to and/or post your original design Thanks.


Test Equipment:  #'s - A        B - D        E - G
H - L        M - O        P - S        T - Z


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