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Tester or Measurement (Instrument) Circuits

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

Last Updated: October 24, 2017 02:55 PM
Circuits Designed by Dave Johnson, P.E. :

Measure Button Battery Cell's Internal Resistance  -  The open cell voltage of a small silver oxide button cell battery remains very close to 1.5 volts over most of the life of the cell.  However, there is a relationship between battery health and the internal resistance of the cell.   This circuit when used . . . Hobby Circuit designed by David A. Johnson P.E.-July, 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:

Machine Vibration Activates Hour Meter -  01/16/97 EDN Design Ideas:  Battery-powered digital hour meters commonly monitor how long a machine is in operation by detecting when the machine is supplied with power.  However, it is often difficult or dangerous to connect a battery-powered hour meter to a line-powered machine.  When the machine being monitored __ Circuit Design by David Johnson, P.E. -  www/discovercircuits/com

Mag Card Reader -  The unit provides the magnetic head on a spring mechanism along with low level head signal amplifiers and data slicers.  Three signal lines coming from the unit provide card presence, clock, and data.  When actively reading a card, it draws about 50ma of current at 5 volts.   __ Designed by Luhan Monat-Mesa Arizona

Maglev Demonstrator -  if you hold two permanent magnets close together, you see that one of them will jump strongly toward (or away) from the other.  in 1842, Samuel Earnshaw expressed the perversity of inanimate magnetic objects in his theorem.   __ Designed by Barry Hansen

Magnetic Card Reader -  The unit provides the magnetic head on a spring mechanism along with low level head signal amplifiers and data slicers.  Three signal lines coming from the unit provide card presence, clock, and data.  When actively reading a card, it draws about 50ma of current at 5 volts.   __ Designed by Luhan Monat-Mesa Arizona

Magnetic Field Receiver -  There are two approaches for receiving the signals, a loop or coil antenna that picks up magnetic fields or a whip or wire antenna that picks up the electric field. (Nature manages to make electromagnetic waves at these frequencies but you cannot make an "electromagnetic" or tuned antenna,  __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

Magnetic Gun -  When optimally tuned, it will propel a small slug about 1.5 metres high, or 2.5 metres horizontally.  IC 1 is a 555 timer in astable mode, sending approx.10 ms pulses to decade counter IC 2.  IC 2 is continually reset through R3, until pin 15 is taken low through the "Fire" button __ Designed by Rev. Thomas Scarborough

Magnetic Levitation -  Suspend objects in midair! __ 

Magnetic levitation -  if you hold two permanent magnets close together, you see that one of them will jump strongly toward (or away) from the other.  in 1842, Samuel Earnshaw expressed the perversity of inanimate magnetic objects in his theorem.   __ Designed by Barry Hansen

Magnetic levitation Device -  Here's the schematic of the device depicted in the photo.  Each of the ten coil-assemblies has its own copy of the above circuit.  The SS41 is a Microswitch Hall Effect magnetic field sensor IC that I found in Surplus catalog for $.50 each.  Any similar hall IC should work __ Designed by William J. Beaty

Magnetic Proximity Switch -  Here is an interesting circuit for a magnetic proximity switch which can be used in various applications. The circuit, consists of a reed switch at its heart.  When a magnet is brought...__ Electronics Projects for You

Magnetic-field probe requires few components -  12/15/06  EDN Design Ideas:  Hall-effect sensor and DMM explore stray fields __ Circuit Design by Sandeep M Satav and VV Rama Sarma, EMI-EMC Centre, RCI, Hyderabad, India

Magnetic-Radiation Remote-Control -  Short-range 35KHz operation, single-channel units; Simple circuitry, no outer antennas required __ Contact Flavio Dellepiane, fladello @ tin.it

Magnetometer -  The Sun with its immense energy stores and close proximity to Earth is a great celestial object to monitor at all wavelengths.  What's more, one can monitor activity on the Sun via indirect means.  More precisely, it is possible to detect solar activity by monitoring the Earths magnetic field.  it's also possible to detect solar activity such as solar flares by monitoring Very Low Frequency (VLF) signal paths which use the ionosphere as a means of propagation __ Contact Joel.Gonzalez @ backyardastronomy.net

Magnetoresistive Angle Measurement  -  Data is collected by turning the center rod and comparing the two evaluation software display readings.  Knowing these values allows a more precise mapping of voltage to digital code.  The second method is to spin the magnet through a 180° range while the software automatically identifies the values__ Analog Devices from the Lab

Mains Box Heat Monitor -  This simple circuit monitors the mains distribution box constantly and sounds an alarm when it senses a high temperature due to overheating, helping to prevent disasters caused by any sparking in the mains box due to short circuits.  it also automatically switches on a bright white LED when the power fails.  The LED gives ample light to check the mains box wiring or fuses in darkness.  The circuit beeps once when power fails and again when power resumes.   __ Designed by D. Mohan Kumar

Mains Voltage Indicator -  This is a circuit for a digital mains voltage indicator that displays main voltage in the form of a LED bar graph with 16 LEDs.  The first LED indicates voltage level at 50 V and the 16th LED shows voltage level for 280 V__ Electronics Projects for You

Make a Fire-alarm System for Your House! -  Many buildings and homes need smoke detectors to alarm at the initial stage of a developing fire accident.  To prevent damage, smoke detectors perform… __ Designed by Upasana Dewan

Make a Joule Thief -  it's a little wisp of a circuit that allows you to drive a blue or white LED from a low voltage.  Normally, if you want to light up a blue or white LED you need to provide it with 3, 3.5 V, like from a 3 V lithium coin cell.  But a 1.5 V battery like a AA cell simply will not work.  But using the Joule Thief, it works like a charm.  Not only does it work with a brand new battery, but it works until the battery is nearly dead-- down to 0.3 V.  That's well below the point where your other toys will tell you the battery is dead, so it can steal every last joule of energy from the battery (hence the name).  To learn how to make one, watch the video, which is available in a variety of formats.  __ Evil Mad Scientists Laboratories

Make a Low Cost Benchtop Power Meter -  09/11/98 EDN Design Ideas:  NOTE:    FILE
has several circuits, please scroll to find this one.  With a few inexpensive ICs  and passive components, you can easily make a multirange power meter suitable for use on your benchtop.  The circuit in Figure 1 measures currents from microamps to amps and voltages as high as 100V.  The voltage at VOUT, which you can monitor with a DVM, indicates the load's power. __ Circuit Design by Jim Todsen, Burr-Brown Corp, Tucson, AZ

Make a Simple Circuit Battery Status Monitor -  Monitor battery status with this easy electric circuit project - no skill required! .   __ Designed by REUK-Renewable Energy UK website

Make a Simple Circuit PC-Based frequency meter  -  04/29/99  EDN-Design ideas –  NOTE:  Scroll to find this circuit.   A simple, low cost, and precision frequency meter uses only two pins of a pc parallel port (Figure 1). The TTL-level periodic input signal with frequency fiN connects to the ACK pin of LPT1. __ Circuit Design by Radovan Stojanovic, University of Patras, Patras, Greece

Make a Simple Earth Leakage Circuit Breaker (ELCB) -  An Earth leakage circuit breaker unit will silently monitor the electrical condition of your appliances and the Earth connection of your house.  if anything goes wrong with them it will instantly switch off the mains and stop any further associated loss.  A simple ELCB circuit is discussed here. __ Designed by hitman

Make a Simple Earth Leakage Circuit Breaker (ELCB) -  A simple earth leakage indicator circuit discussed here can be used for getting some very useful results regarding current leakages from an appliance body into the earth pin.   __ Designed by Swagatam Majumdar

Make Better RMS Measurements with Your DMM an 1392 -  Application Note__ Aligent

Make Your Own Shunts -  Using a modern multimeter to measure current can sometimes be difficult.  Many of these meters will only measure up to one amp.  However, may 112-volt DC powered projects draw a lot more than that.  if you have ever thought of purchasing a commercial shunt to solve the problem, your know just how expensive they can be.  Commercial shunts, while very precise, frequently cost more than the projects they are measuring! However, there is a better and cheaper alternative that will work perfectly well in most situations __ Designed by Tony van Roon  VA3AVR

Making High Accuracy Temperature Measurements with the 3499 an 1460 -  Application Note__ Aligent

Making High-Accuracy Temperature Measurements with the 34970A Data Acquisition Unit -  Application Note__ Aligent

Many other PC Controlled Data Acquisition Devices -  ver the last 15 years I have designed many small, low cost Data Acquisition devices.  These have been built with PC Parallel Port, Serial Port and more recently USB control.  Most of these devices have been built for one or two specific jobs.  With the advent of ActiveX controls and their usability with a wide range of software programs these designs have been superseded by the more universal PIC -DAS system.   __ Designed by Steve Hageman

MAR/RAM Test Fixture Instructions -  App Note  AN-60-018__ MiniCircuits.com

M-Audio Recorder Use -  it easily outperforms my soundcard!  But there is a problem (as usual).  The device emits a huge amount of hum and buzz and a receiver can't be anywhere near it.  A lot of it sounds just like 60 Hz line noise, too, making it more confusing.  I came up with a solution that completely eliminates the interference  __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

MAV Test Fixture Instructions -  AN-60-025 Application Note__ MiniCircuits.com

MAX038 Function/Sweep Generator with Markers ATtiny2313, AT90S1200A -  Maxim's MAX038 function generator chip is capable of producing nearly constant amplitude sine, square, and triangle waves with a low output impedance, from a very low frequency to more than 20 MHz.  Basically, a function generator on a chip.  Here is a function/sweep generator that uses the MAX038 chip.  The design described on these pages are not so much instructions for duplicating the design as they are a collection of ideas to stimulate your own thoughts __ Designed by Dick Cappels

MAX6953 Development board -  The MAX6953 from Dallas Maxim is a compact cathode-row display driver that interfaces a microprocessor (like PIC  or AVR) to four 5x7 dot matrix LED display trough an i2C compatible serial interface.  The chip includes some features that can help us to handle easier the displaced data. __ Contact Kedros Loannis

Maximum Voltage Sorter Uses Analog Multiplexer -  09/29/94 EDN Design Ideas:  The voltage-sorting circuit in Fig 1 continuously finds the maximum of eight input voltages and the corresponding binary address with the aid of two analog multiplexers, IC 1 and IC 2.  The circuit compares each input sequentially with the current maximum voltage and updates the maximum voltage and address when it finds a new maximum __ Circuit Design by Alan L Giles, Tao Systems, Hampton, VA

Measure –48V high-side current -  02/21/08  EDN Design Ideas:  This circuit measures –48V high-side current using a single positive supply.   The nominal –48V rail, which finds wide use in wireless base stations and other telecommunications equipment in network central offices, can vary from –48 to –60V.  Measuring its current draw typically requires components that operate on ±15V dual supplies.  Eliminating the negative supply would reduce system complexity and cost.  This Design idea uses an AD629 difference amplifier and an AD8603 operational amplifier, both from Analog Devices, to measure current at –48 to –60V and operates from a single positive-power supply (reference 1 and reference 2). __ Circuit Design by Wenshuai Liao

Measure an Amplifier's THD Without External Filters -  01/05/12  EDN Design Ideas:  Adding a secondary amplifier boosts the THD to measurable levels.  Measuring an op amp’s THD (total harmonic distortion) at frequencies below 100 kHz is problematic because modern amplifiers have a THD rating that is much lower than that of most test equipment.  The circuit in this Design idea uses active noise amplification to eliminate the need for external filters.  This approach allows you to measure THD at several orders of magnitude lower than the resolution of the test fixture you are using.   __ Circuit Design by Ken Mendez, Maxim Integrated Products, Sunnyvale, CA

Measure Button Battery Cell's Internal Resistance  -  The open cell voltage of a small silver oxide button cell battery remains very close to 1.5 volts over most of the life of the cell.  However, there is a relationship between battery health and the internal resistance of the cell.   This circuit when used . . . Hobby Circuit designed by David A. Johnson P.E.-July, 2006

Measure Crystal Q -  A reader saw a photo of my old W7ZOI crystal characterization oscillator (with the suggested switch from Dr.  Gordon-Smith, G3UUR) in the site archive.  I had removed its crystal holders to yet another such oscillator and just soldered in a crystal as a PROP for the photo.  This photo "suggested" it was OK to solder in the various crystals under test.   __ Contact Vasily Ivanenko

Measure humidity & temperature on one TTL line -  08/30/01 EDN Design Ideas:  By combining the responses of an Analog Devices (www. Analog.com] AD590 temperature sensor and a Humirel (www.humirel.com] HS1101 humidity sensor, you can generate a single TTL-level signal containing information from both sensors (Figure 1).  This design uses a 74HC123 monostable multivibrator, IC 1, to form a free-running oscillator __ Circuit Design by Shyam Tiwari, Sensors Technology Pvt Ltd, Gwalior, India

Measure inductance & capacitance over a wide range -  EDN Design Ideas:  11/25/2013    Measure inductors and capacitors over a very wide range of values with this simple circuit __ Circuit Design by John Fattaruso

Measure inductance with DC superimpose -  07/06/95 EDN Design Ideas:  in some applications, magnetic components are difficult to characterize when steady-state current is flowing.  Bridges having the necessary dc capability are expensive.  if you don't need extreme precision (for example, 2% or better) , other measurement methods exist.  The method in Fig 1 is universally applicable over a range of inductances and frequencies.  The basis for the inductance measurement is to determine the ac impedance at the frequency (f) , ideally the inductor's working frequency of interest.   __ Circuit Design by HB Farensbach,  Consultant, Albano, Italy

Measure Motor Speed Uses Low-Cost Components -  11/08/07  EDN Design Ideas:  A microcontroller-based circuit provide as both an LCD readout and an analog motor-speed output __ Circuit Design by R García-Gil, J Castelló, and JM Espí, Escola Tècnica Superior d’Enginyeria, University of Valencia, Spain

Measure nanoamps to ensure accurate computer clocks -  10-May-07 EDN-Design ideas This EDN Video Design ideaexplains why PC clocks are invariably wrong, and how engineers can surmount the extreme measurement challenge involved in solving the problem __ Circuit Design by Jim Williams, staff scientist with Linear Technology

Measure open-circuited cables using a multimeter -  09/26/02 EDN Design Ideas:  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 __ Circuit Design by Ron Duffy, Agilent Technology, Colorado Springs, CO

Measure Optocoupler's Response Time -  09/08/11  EDN Design Ideas:  Measure the response speed of optocouplers in order to select matching devices.  You can use the circuit in this Design idea to measure the attack and release times of photoresistor-type optocouplers (Figure 1).  Such devices often find use in audio compressors or volume-control circuits.  The design uses an oscillating Schmitt trigger with the optocoupler DUT (device under test) in the feedback loop.  The photoresistor and resistor R1 form a voltage divider that controls the input of the Schmitt trigger.   __ Circuit Design by Peter Demchenko, Vilnius, Lithuania

Measure power-line distortion with a mixed signal THD analyzer -  11/22/07 EDN Design Ideas:  A mixed-signal total-harmonic-distortion-analyzer device measures the distortion of the mains ac voltage __ Circuit Design by John R Ambrose, Mixed Signal Integration, San Jose, CA

Measure power-on current transients on AC line -  11/11/99 EDN-Design ideas - For any electronic or electrical system, you usually determine the ac-line fuse rating based on the steady-state current.  However, the power-on current surge is an important parameter in determining the fuse's I 2 t rating.  The I 2 t rating is a measure of the energy required to blow a fuse in pulsed conditions.    __ Circuit Design by N Kannan

Measure Resistance & Temperature with a Sound Card -  EDN-Design ideas -- 05/26/11    Measure resistance and use free software to convert to temperature.  Unless you add a measurement instrument to your computer, you have only the sound card as an analog i/O port.  You can use the sound card to digitize ac analog voltages but only within a limited range.  You can, however, add some signal processing and measure a wider variety of signals, even those that produce dc or low-frequency outputs.  For example, you can directly connect a thermistor to make a sound-card thermometer to monitor or record the temperature on PCBs (printed-circuit boards) , circuits, heat sinks, and more.
 __ Circuit Design by Zoltan Gingl and Peter Kocsis, University of Szeged, Szeged, Hungary

Measure resonator Q at VHF -  I've long enjoyed broadcast FM DX chasing.  This post covers the first chapter in my pursuit to design and make a homebrew broadcast (wideband) FM DX receiver. __ Contact Vasily Ivanenko

Measure RH with instrumentation-grade system Monitor -  EDN Design Ideas:  04/30/2014     An accurate, modern system monitor chip senses humidity the old-fashioned way __ Circuit Design by LTC Design Note

Measure settling time to 1 ppm -  03/04/10  EDN Technical Article: intense, extensive, and protracted effort yields a measurement circuit with 20-bit resolution.  nstrumentation, function generators, inertial navigation systems, ATE (automatic test equipment) , medical apparatus, and other precision applications now require 18-bit converters.  The resolutions of these converters are so precise that measuring various performance parameters is difficult.  DACs’ dc specifications are relatively easy to verify, but their ac specifications require more sophisticated approaches to produce reliable information.  A DAC’s settling time is the elapsed time from an input code application until the output remains within a specified error band around the final value.   __ Circuit Design by Jim Williams, EDN's most revered contributor, passed away in June 2011 after a stroke.  He was 63.

Measure Small Current in DC Servo Motor -  12/06/01 EDN Design Ideas:  The simple Circuit design in Figure 1 lets you measure all components of a current flowing in a dc servo motor.  The rectified output of the circuit uses ground as a reference, so you can measure the output by using a single-ended A/D converter.  The current-sense resistor, R1, has a value of 0.1Ω  __ Circuit Design by Shyam Tiwari

Measure Small Currents Without Adding Resistive Insertion Loss -  EDN-Design ideas -- 07/28/11    Floating current to voltage converter can be inserted in-line with no voltage drop and no need for a ground reference.  in most cases, you measure current by converting it into a proportional voltage and then measuring the voltage.  Figure 1 shows two typical methods of making the conversion.  in one method, you insert a probing resistor, RP, in series with the current path and use differential amplifier IC 1 to measure the resulting voltage drop (Figure 1a).  A second method is a widely known operational amplifier current-to-voltage converter in which inverted IC 1’s output sinks the incoming current through the feedback resistor (Figure 1b). __ Circuit Design by Maciej Kokot, Gdansk University of Technology, Gdansk, Poland

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


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