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Tester or Measurement (Instrument) Circuits

Test Equipment:  #'s - A        B - D        E - G
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Last Updated: October 24, 2017 02:55 PM
Circuits Designed by Dave Johnson, P.E. :

Precision AC Peak Detector -  This unique circuit uses a very inexpensive voltage comparator to form a peak detector.  The DC voltage produced tracks the positive peak of the input signal.  it works from about ten millivolts to about 10 volts peak to peak.  The maximum frequency is about. . . Circuit by David A. Johnson P.E.-February, 2002

Precision Low 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 . . . Hobby Circuit designed by David Johnson P.E.-December, 2004

Produces Beep once each Minute -  This circuit produces a short beep once each minute.  it is powered directly off the 120vac power line to remind you that a device connected to the circuit is turned on.  it is simple enough to be packaged inside a small plastic box . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

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:

Precision AC Peak Detector -  This unique circuit uses a very inexpensive voltage comparator to form a peak detector.  The DC voltage produced tracks the positive peak of the input signal.  it works from about ten millivolts to about 10 volts peak to peak.  The maximum frequency is about. . . Circuit by David A. Johnson P.E.-February, 2002

Precision Audio Frequency Peak Detection Probe  -  This is a handy companion for a digital voltmeter.  its allowed me to do a lot of things I used to use my oscilloscope for, and in addition it measures voltages to much greater precision.  Using an LM324 quad op amp, this peak detector provides 2% measurement accuracy on square waves from 5 Hz to 20 kHz.   __ Designed by Dick Cappels

Precision Audio Millivoltmeter -  Measures10mV to 50Volt RMS in eight ranges Simply connect to your Avo-meter setAT 50µA range __ Contact Flavio Dellepiane, fladello @ tin.it

Precision capacitance meter -  10/22/13  EDN Design Ideas:  There's an art to capacitance measurement.  What do you think of this rendition?  __ Circuit Design by Francesc Casanellas

Precision Capacitive-Sensor Interface Suits Miniature Instruments -  24-Jul-08 EDN Design Ideas:  A pair of one-shots develops a voltage proportional to the value of a capacitive sensor and transmits these readings via a LVDS interface __ Circuit Design by Jiaqi Shen and Xiaoshu Cai, University of Shanghai for Science and Technology, Shanghai, China

Precision Current Monitoring for Electric Motors, Solenoids & Inductive Loads -  Current information in electric motors and solenoids provides important insight into power output and system health.  Electric motor and solenoid driving circuits and the devices themselves create a challenging environment for operation of current monitoring circuits, with large common mode voltage shifts, fast switching currents __ Linear Technology/Analog Devices App Note, Culyer Latorraca Mar 21st 2011

Precision Current Sink -  A non-inverting amplifier configuration can force an input control voltage across a ground referred resistor.  This creates a precise amount of current flow.  This current must be sunk by the external transitors so the same amount of current flows to ground from a positive supply referred load circuit.  __ Linear Technology/Analog Devices App Note, Jun 21, 2011

Precision Digital Altimeter -  The current concept incorporates a wireless transmitter and receiver and is thought to be used for remote controlled airplanes or appliances with two separate parts.  in other words, we have one dedicated transmitter (acquisition, filtering) and one dedicated receiver part (user-interface, look-up table, calibration, storage) , capable of being connected__ 

Precision Frequency Marker -  Recently, cheap TCXO modules with a frequency of 12.8MHz are on the surplus market (at least in Japan).  TCXO stands for Temperature Compensated X'tal Oscillator.  it is a fine-tunable oscillator module packed in a small can with an excellent frequency stability against ambient temperature change.   __ Designed by MINOWA, Makoto  7N3WVM

Precision High Voltage High Side Load Current Monitor (1754) -  The LT6016/LT6017 are dual and quad rail-to-rail input operational amplifiers with input offset voltage trimmed to less than 50μV.  These amplifiers operate on single and split supplies with a total voltage of 3V to 50V and draw only 315μA per amplifier.  The Over-The-Top input stage of the LT6016/LT6017 is designed to __ Linear Technology/Analog Devices App Note, Dec 4th 2012

Precision Low 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 . . . Hobby Circuit designed by David Johnson P.E.-December, 2004

Precision LVDT Signal Conditioning using Direct RMS to DC Conversion -  DN362 Design Notes__ Linear Technology/Analog Devices

Precision peak Detector uses no precision components -  10-Jun-04 EDN Design Ideas:  When you need a precision peak detector, you would usually implement it with one or several op amps and a few other associated components.  This technique usually works well unless your design requires operation higher than a few kilohertz.  in designs requiring such operation, the accuracy of the circuit severely deteriorates unless at least one of the amplifiers has a high slew rate and frequ __ Circuit Design by Jim McLucas, Longmont, CO

Precision T/C Amplifier with cold junction compensation for the BS2 -  A thermocouple signal is quite small, and the long thermocouple leads often induce quite a bit of noise into the system.  This new circuit is far more accurate, stable, and less immune to noise.  it makes use of a Linear Technologies LT1025 chip to provide CJC (Cold Junction Compensation) , an LTC1098 8-bit 2-channel Analogue to Digital Converter, and an LTC1050 chopper amp.  The feedback resistors are designed to deliver 5V (full scale signal) to the ADC with a 1000 degree C.  Type K signal.  The 1050 is a great amplifier, delivering "rail to rail" output which makes powering the circuit simple.  __ 

Precision Temperature Controller Has Thermal-Gradient Compensation -  06/12/08  EDN Design Ideas:  An electronic work-around cancels the effects of thermal gradients in the load's thermal impedances __ Circuit Design by W Stephen Woodward, Chapel Hill, NC

Precision Temperature Logger & Controller, Part 1 -  This Temperature Logger & Controller is based on the Dick Smith Electronics Q1437 digital thermometer.  it records & displays two temperature channels once a second on a PC over a period of up to 12 hours.  With appropriate thermocouples, temperatures from -200?C to +1300?C can be recorded, with the display range, resolution, and temperature program adjustable in real time while the data is being logged.__ SiliconChip

Precision Tilt/Fall Detector Consumes Less Than 1.5 Mw -  3-Dec-09 EDN Design Ideas:  Detect X-axis position and indicate it with an LED __ Circuit Design by Marián Stofka, Slovak University of Technology, Bratislava, Slovakia

Precision Voltage Reference for Multimeter Calibration -  Recently I wanted to adjust the end-of-charge voltage of a solar charge controller.  I failed.  Each time I checked the state of charge the result was different from my previous adjustments.  After several days I found out that the problem was not the charge controller or the battery but just the fact that I used two different multimeters.  The multimeters simply showed different voltages.__ 

Precision VXO for Crystal Characterization & Matching -  The Precision VXO (PVXO) and its matching Crystal Test Fixture (CTF) were created to provide a low cost means of evaluating the characteristics of crystals and a means of measuring their series resonant frequency.  With this information, one can then build very low cost, high performance, crystal filters for receivers and transmitters.  The PVXO was kitted by the NJ QRP Club, but has since sold out those units.  However, photos of that unit are available on this page for completeness __ Designed by Jim Kortge, K8IQY

Precision Wideband Current Probe for LCD Backlight Measurement -  DN101 Design Notes__ Linear Technology/Analog Devices

Pressure Gauge Responds Linearly to Altitude -  03/03/94 EDN Design Ideas:  You can use a common pressure transducer as an altimeter if you employ a special technique to make the transducer respond linearly.  if you were to simply amplify the output of a pressure gauge's bridge (VB in Fig 1]by a gain of 32.7 and an offset of 3.2V, such a circuit would produce an output of0V at sea level and 1V at 10, 000 ft.  However, this simple design would read 38.5 mV (385 ft], which is too high at 5000 ft.  The nonlinear relationship between atmospheric pressure and altitude causes the error, which peaks at 3.85% of full scale __ Circuit Design by Bruce C Trump, Burr-Brown Corp, Tucson, AZ

Pressure Sensor Alarm -  General purpose circuit of the simple pressure sensor alarm is built around a couple of readily available cheap components.  Working of this circuit is straight forward and self-explanatory.  When the circuit is powered by a 9V compact battery, the active piezo-sounder at the output of IC 1 starts beeping for a short time and __ Designed by Popescu Marian

Pressure Sensor-Based Altimeter -  The circuit uses an absolute pressure sensor to measure barometric pressure, it depends on the altitude but not linearly, remember this when using the circuit.  The pressure sensor can be absolute or differential, this means that the output depends on absolute pressure or on the pressure difference between two ports of the device.  it is a four terminal device: if a current flows between terminals 1 and 3 the DDP found between pins 2 and 4 is (almost) proportional to pressure (absolute or differential).  The output depends on the current and on temperature, therefore, this must compensated.  The output is very small so we need amplification.   __ Designed by Paolo Zini

Pressure-Sensitive Alarm -  Here is a low-cost, pressure-sensitive burglar alarm.  The alarm uses a home-made pressure sensor, which works as a variable capacitor using two copper-clad boards and a piece of sponge in between...__ Electronics Projects for You

Presure based hit switch -  This versatile hit switch is the electronics equivalent of a conventional switch.  it can be used to control the switching of a variety of electronic devices.  The circuit of the hit switch uses a piezoelectric diaphragm as the hit sensor.  A piezoelectric material develops electric polarization when strained by an applied stress.  The hit sensor makes use of this property.__ 

Prevent Deep Discharge of Battery -  09/26/96 EDN Design Ideas:  NOTE:    Page includes several designs, scroll to find this one.  mCs such as the 8051 and 8096 and UARTs such as the 82510 provide hardware support for a multiprocessor asynchronous serial-communication protocol (MicroLan].  This featu __ Circuit Design by Rolando Herrero, Instituto Tecnologico de Buenos Aires, Argentina

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.    __ Circuit Design by Glenn J Keller,  The 3DO Company, Redwood City, CA

Probing System Lets You Test Digital ICs -  06/20/12  EDN Design Ideas:  Build a test jig and a combination logic and stimulus injector probe. __ Circuit Design by Raju Baddi, Tata Institute of Fundamental Research, Pune, India

Probing the Limits Of LOGIC SYNTHESIS -  03/17/94 EDN Design Ideas:  Logic synthesis has freed designers from the complexities of gate-level design by converting RTL descriptions to optimized gate-level logic.  But ASIC , FPGA, and CPLD designers are still constrained by a dependence on silicon.  Designers will need to pay more-not less-attention to layout as silicon densities continue to increase.    __ Circuit Design by -Ray Weiss, Technical Editor

Procedure Tests Transducer -  03/01/96 EDN Design Ideas:  Testing electromechanical transducers can be as simple as measuring a dc voltage.  The circuit in Figure 1 and an accompanying test method enable you to measure the damping coefficient ([beta]) of speakers, microphones, seismic geophones, and other transducers that exploit electromagnetic phenomena.  You can also tailor this method for testing electrostatic devices, such as capacitive micromachined sensors.  in general, you can measure the damping in any second-order system or signal, which conforms to the following basic equation for the free transient process __ Circuit Design by Alexander Belousov, SMP Inc Long Island City, NY

Produce a Less than 25 Nsec Pulse -  05/11/00 EDN Design Ideas:  in many testing situations, a circuit that can produce a short pulse is useful.  You can use a short pulse to test trigger or interrupt-pulse-width requirements and to mimic glitches or noise on inputs, for example.  in some cases, short pulses with long delays between them are desirable.  For these cases, a function generator is inadequate because you can reduce the duty cycle low enough to produce low-nanosecond pulse widths only at relatively high frequencies.  Although purely analog circuits can generate short pulses, input and output loading and buffering propagation delays create problems with interfacing them to TTL-compatible circuitry.   __ Circuit Design by Andy Brandenberger, National Instruments, Austin, TX

Produces Beep once each Minute -  This circuit produces a short beep once each minute.  it is powered directly off the 120vac power line to remind you that a device connected to the circuit is turned on.  it is simple enough to be packaged inside a small plastic box . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

Programmable Continuity Tester -  Our go/no-go continuity tester giving you the ability to set minimum continuity.__ SiliconChip

Programmable Continuity Tester -  Easy-to-build unit lets you set the continuity "pass" threshold to anywhere between 1Ω and 100Ω.  it makes an ideal go/no-go tester.__ SiliconChip

Programmable Electronic Thermostat -  it's programmed using a PC and has three relays to control external equipment.__ SiliconChip

Programmable oscillator uses digital potentiometers -  03/07/02 EDN Design Ideas:  Digital potentiometers are versatile devices; you can use them in many filtering and waveform-generation applications.  This design idea describes an oscillator in which setting the resistance of two digital potentiometers independently programs the oscillation amplitude and frequency.  Figure 1 shows a typical diode-stabilized Wien-bridge oscillator that generates accurate sine waves fro __ Circuit Design by Alan Li, Analog Devices, San Jose, CA

Programmable PIC-Powered Timer -  This PIC -based timer can be set for any period from one second up to 680 days and even (theoretically) up to nearly 60 years.__ SiliconChip

Programmable Window Comparator Uses a Single Reference -  Voltage-monitoring circuit is based on Microchip 12F675 MCU Lets users set up a tolerance around a specific value A voltage monitor is a common hardware need.  But beyond a simple compare, many systems must provide a tolerance around a __ Designed by William Grill is the electronic

Project-Magnetic Levitation -  With this assembly, I was able to suspend a magnet about 1" below an electromagnet.   Here are the details on the circuit design.  This project requires you to have some familiarity with building and testing electronic circuits.   A great way to start is to obtain an "Engineer's Mini-Notebook" book from Radio Shack, by Forrest M.  Mims iii, on building circuits.   He has a lot of different booklets out for all sorts of projects.   They go into a fair amount of detail so you'll start to learn how the circuits work, how to put things together, etc. __ Designed by Rick Hoadley

Propane Leak Detector -  Can also detect Other Hydro-Carbon Gases.   __ Designed by G.L. Chemelec

Protect Battery from Overdischarge -  04/12/01 EDN Design Ideas:  All electronic circuits powered by a battery discharge the battery.  in some applications, it is undesirable to overdischarge the battery, because it could irreversibly reduce the battery’s capacity and the number of discharge/charge cycles.  The circuit in Figure 1 protectsPDF contains multiple circuits, scroll to find this circuit __ Circuit Design by Martin Wuzik, Implex AG Hearing Technology, Ismaning, Germany

Protection of USB Port from Overvoltage & Overcurrent -  The LTC4362 monolithic overvoltage/overcurrent protector safeguards 2.5V to 5.5V systems from power supply overvoltage.  it is designed for portable devices with multiple power supply options including wall adaptors, car battery adaptors and USB ports.  __ Linear Technology/Analog Devices App Note, Jul 8th 2011

Provide Accurate RTD Measurements -  12/31/69  EDN Design Ideas:  The circuit in Figure 1 is an efficient measuring circuit for PT100 RTD elements.  IC 1 provide as an accurate 2.5V output and, together with P1 and R1 , also provide as a stable 1-mA current to the RTD element.  The output of IC 2 is –0.1V.  P2 provide as a zero ad __ Circuit Design by Tito Smailagich, ENIC, Belgrade, Yugoslavia

Provide Cold-Junction Compensation -  11/28/02  EDN Design Ideas:  The accuracy of any circuit or system that uses a thermocouple to determine the temperature of a process is limited by the accuracy of the method used to perform cold-junction compensation.  in a thermocouple measurement, two wires  __ Circuit Design by Mark Maddox, Analog Devices, Wilmington, MA, and John Wynne, Analog Devices, Limerick, Ireland

Provide High-Side Current-sensing -  04/24/97  EDN Design Ideas:  in power supplies or battery chargers, you often need information about the current flowing in the high-side rail.  Figure 1 shows a common circuit for obtaining this information.  The circuit provide as a ground-referenced voltage proportional to the current __ Circuit Design by M Ossmann

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Test Equipment:  #'s - A        B - D        E - G
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