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Tester or Measurement (Instrument) Circuits

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Last Updated: December 07, 2017 02:04 PM
Circuits Designed by Dave Johnson, P.E. :
Gas_Fireplace_Fizzle   -  Gas fireplace won't turn always turn on consistently. The pilot light was always on.  As illustrated below, a typical gas fireplace has a small pilot light flame.  The long term solution would be to replace the thermopile.  But, in the short term, the modification below would keep the thing going for another year or two.  As shown below, the solution was to connect a supercapacitor across the thermopile. This device acts like a battery and would provide the needed peak current to open the valve.  A 4.7 farad device was sufficient. . . . Dave Johnson, Lubbock TX-DC Magazine - Issue 4 Dec 2009

Generate Short Delayed Pulse -  This circuit generates a short 10ms pulse 15 minutes after a “start” pushbutton switch is activated . . . Hobby Circuit designed by David Johnson P.E.-October, 2005Ground Resistance Tester -  UL requires that an electrical system using a metal chassis earth ground connection have a resistance of less than 0.1ohms.    This resistance must be tested with actual line current in excess or 10 amps.    The circuit shown uses a couple of LEDs to indicate . . . Hobby Circuit designed by Dave Johnson P.E.-April, 2001

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:

Full Wave Rectifier -  This is a classic circuit that can accurately convert an AC signal to DC.  At 40KHz the input signal can be as low as 0.05 volts peak to peak.. . . Circuit by David A. Johnson P.E.-July, 2006

Full-Bridge Amplification using a Resistor Arrays to Provide Precise Matching in Excitation Amplifier -  This example provide excitation using resistor arrays to produce precise gain.  The circuit is configured to provide 10V and –5V excitation to the bridge, producing a common mode voltage at the input to the LTC2430/LTC2431 of 2.5V, maximizing the AC input range for applications where induced 60Hz could reach amplitudes up __ Linear Technology/Analog Devices App Note, Apr 29th 2010

Full-Bridge Amplification using a Single Amplifier -  This example shows a single amplifier being used to produce single-ended gain.  This topology is best used in applications where the gain setting resistor can be made to match the temperature coefficient of the strain gauges.  if the bridge is composed of precision resistors, with only one or two variable elements, the reference __ Linear Technology/Analog Devices App Note, Apr 29th 2010

Full-Bridge Amplification using Autozero Amplifiers to Reduce Input Referred Noise -  This circuit shows an example of a simple amplification scheme.  This example produces a differential output with a common mode voltage of 2.5V, as determined by the bridge.  The use of a true three amplifier instrumentation amplifier is not necessary, as the LTC2430/LTC2431 have common mode rejection far beyond that of most __ Linear Technology/Analog Devices App Note, Apr 29th 2010

Full-Bridge Load Current Monitor -  The LT1990 is a micropower precision difference amplifier with a very high common mode input voltage range.  it has pin selectable gains of 1 or 10.  The LT1990 operates over a ±250V common mode voltage range on a ±15V supply.  The inputs are fault protected from common mode voltage transients up to ±350V and differential voltages __ Linear Technology/Analog Devices App Note, Apr 5th 2010

Fully Isolated AC Power & Current Monitor -  This circuit highlights the use of the LT2940 in power and current monitoring in an isolated AC application.  The LT2940 excels in this type of applications since it can monitor where both the current and the voltage may be variable due to supply voltage uncertainty, component parametric changes, transient conditions, time-varying__ Linear Technology/Analog Devices App Note, Apr 26th 2010

Fully Isolated Lithium Ion Battery Monitoring & Protection System  -  Launch the evaluation software and connect the USB cable from the PC to the USB mini-connector on the SDP-B board__ Analog Devices from the Lab

Function generator based on 8038PCD -  Built around a single 8038 waveform generator IC , this circuit produces sine, square or triangle waves from 20Hz to 200kHz in four switched ranges.  There are both high and low level outputs which may be adjusted with the level control.  This project makesa useful addition to any hobbyists workbench as well __ Designed by Andy Collison

Fundamentals of RF & Microwave Power Measurements -  Application Note__ Aligent

Fundamentals of Signal Analysis -  Application Note__ Aligent

Fuse Monitor/Alarm -  a simple way to see if a fuse has blown without removing it from its holder __ Designed by Andy Collison

G Strain energy absorber -  it is important to know that transistors Q1, Q2, Q3 must not work like an astable (tri-phase) multivibrator (you could verify it on scope (no square waves but NON LiNEAR wave between XB, YB, ZB must be displayed on the scope). __ Designed by Jean-Louis Naudin

Gali Test Fixture Instructions -  AN-60-013 Application Note__ MiniCircuits.com

Gali-TBF Test Fixture Instructions -  AN-60-015 Application Note__ MiniCircuits.com

Galvanic Skin Response (GSR) -  Medical and health related electronic circuit diagrams / circuit schematics__ 

Game Show Indicator Lights (Who's First) -  This circuit turns on a light corresponding to the first of several buttons pressed in a "Who's First" game.  Three stages are shown but the circuit can be extended to include any number of buttons and lamps.  Three SCRs (silicon controlled rectifiers) are connected with a common cathode resistor (50 ohm) so that when any SCR conducts, the voltage on the cathodes will rise about 7 volts above the voltage at the junction of the 51K and 1K ohm resistors and prevent triggering of a second SCR.  When all lamps are off, and a button is pressed, the corresponding SCR is triggered due to__ 

Gamma-photon Detector -  04/24/03  EDN Design Ideas:  LED driver delivers constant luminosity - The circuit of Figure 1 includes a PIN photodiode that detects individual photons of gamma radiation.  The reverse bias on the photodiode sometimes creates a depletion region.  When such a ph __ Circuit Design by Bruce Denmark, Maxim Integrated Products, Sunnyvale, CA

Gas_Fireplace_Fizzle   -  Gas fireplace won't turn always turn on consistently. The pilot light was always on.  As illustrated below, a typical gas fireplace has a small pilot light flame.  The long term solution would be to replace the thermopile.  But, in the short term, the modification below would keep the thing going for another year or two.  As shown below, the solution was to connect a supercapacitor across the thermopile. This device acts like a battery and would provide the needed peak current to open the valve.  A 4.7 farad device was sufficient. . . . Dave Johnson, Lubbock TX-DC Magazine - Issue 4 Dec 2009

Gas Leakage Alarm -  LPG gas is supplied in pressurised steel cylinders.  As this gas is heavier than air, when it leaks from a cylinder it flows along floor and tends to settle in low...__ Electronics Projects for You

Gas Sensors Sniff Out Danger -  15-Jul-10 -Design News:   Natanel Eizenberg decided to build a sensor module that would detect and measure carbon monoxide and methane to help ensure safe environments for his co-workers and family.  But in addition to creating an alarm circuit, Eizenberg added a wireless link that communicates with a nearby PC.  Adding a __  Gadget Freak-Case #168

Gated oscillator holds last level -  EDN Design Ideas:  09/22/2014     Unlike a typical gated oscillator, this one holds its current output level when turned off __ Circuit Design by Einar Abell

Geiger Counter -  Some people might like this.   __ Designed by G.L. Chemelec

Geiger counter -  Geiger counters are available in all shapes and sizes, but they tend to be quite expensive to buy (typically a couple of hundred US dollars for a simple model, rising to a thousand dollars or more for a professional instrument).  For a first-timer, and/or a reasonably experienced electronics hobbyist, building your own can be a very rewarding alternative__ 

Geiger Counter -  For the short amount of time the GM tube is detecting one particle, if another radioactive particle enters the tube it will not be detected.  This is called dead time.  The maximum dead time for our GM tube is 90 microseconds (or .00009 seconds).  There is a mathematical formula for adjusting a Geiger counter read out to compensate for the GM tube's dead time.  However the adjust is so small that for practical applications it can be ignored.  High-end nuclear work will take a tube's dead time into consideration.   __ Designed by © 2007-2014 Images SI, Inc

Geiger Counters -  Techlib reader Dave Mouat modified the circuit.  These circuits generate high voltages and can cause dangerous shocks!  Do not build these devices unless you are experienced and qualified to work on high voltage devices. __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

Geiger Tube Simulator -  This little gadget will simulate a 500 volt or less Geiger tube when driven by a signal generator of sufficient amplitude, typically 5 volts p-p or greater.  The purpose is to generate a steady, precise number of counts per minute so that the Geiger counter's meter may be calibrated.   __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

Generate Short Delayed Pulse -  This circuit generates a short 10ms pulse 15 minutes after a “start” pushbutton switch is activated . . . Hobby Circuit designed by David Johnson P.E.-October, 2005

Geomagnetic field Detector -  Where there is heat, let us bring cooling: a fan will do the job, but unfortunately fans are usually noisy.  in many cases there is no need for the fan to run continuously at full speed, and so it makes sense to control the fan speed in response to the temperature of the heatsink or device being cooled, switching the fan off entirely if it should fall to room temperature__ 

Ghost Detector -  Yes, you read correctly, it's a ghost detector, assuming ghosts exist and, for some reason, have electric charge.  Ok, this is a changing charge detector.  if a ghost disturbs the electric field in the vicinity of this gadget you will see the results on the LEDs.  Don't hold your breath, unless you wish to become a ghost yourself.  There's a pair 'a normal LEDs that display whether the charge at the antenna is changing in a positive or negative direction (green vs red).   __  Contact:  Lennie Zink

GMR Sensors Manage Batteries -  09/02/99 EDN Design Ideas:  The past few decades have seen remarkable progress in magnetic-sensor technology.  Early and current sensors exploit the Hall effect; more recent devices use an effect called giant magnetoresistance (GMR].  GMR sensors use semiconductor processing of materi __ Circuit Design by D Ramirez and J Pelegri, University of Valencia, Spain - September 2, 1999

GoldPIC 3 Pulse Induction Metal Detector (has electronic kit available) -  GoldPIC  3 is a 'Build it Yourself' pulse induction metal detector design __ Designed by Trevor R. Hill

Good IR Detector -  How to build a simple IR detector, schematics and alternate links  __ Designed by DC Reagan

GPS-based frequency standard -  Using an inexpensive GPS board, it provides atomic clock frequency accuracy to an HF transceiver, and lab equipment. __ Designed by Manfred Mornhinweg

Grid-dip-meters + xtal Tester -  This is a simple XTal tester circuit.  T1 and XTal have formed an oscillator.  C1 and C2 are voltage divider for oscillator.  if the XTal is safe, the oscillator will work well and its output voltage will be rectified by C3, C4, D1 and D2, then T2 will run and LED will light.  The circuit is suitable to test 100KHz, 30MHz Xtal.   __ Designed by Jan-Martin Nøding

Ground Fault Indicator -  Check out your AC Outlets for Possible Hazzards.   __ Designed by G.L. Chemelec

Ground Resistance Tester -  UL requires that an electrical system using a metal chassis earth ground connection have a resistance of less than 0.1ohms.    This resistance must be tested with actual line current in excess or 10 amps.    The circuit shown uses a couple of LEDs to indicat . . . Hobby Circuit designed by Dave Johnson P.E.-April, 2001

Grounded Resistor Tunes Oscillator -  29-May-03 EDN Design Ideas:  To vary the frequency of any sine-wave oscillator, you should use a pair of ganged variable resistors, and you should thoroughly match their characteristics over the entire variation range to satisfy the oscillator's balancing conditions.  This restriction leads to problems in the tuning range and high cost, thereby limiting the range of applications __ Circuit Design by Vladimir Tepin, Taganrog, Russia

GSM Base Station Measurements -  Application Note__ Aligent

Guider Camera Signal Processing & Bias Voltages -  Each signal processing channel features a well-known dual-slope integrator circuit topology, optimized in this case for fast-settling time__ 

Guiding Visually Challenged using Raspberry Pi -  Blindness is a state of lacking the visual perception due to physiological or neurological factors.  Partial blindness represents the lack of integration in growth of the optic nerve or visual centre...__ Electronics Projects for You

Guitar Cable Tester -  Here is a device that musicians will find highly useful.  it will detect breaks or shorts in a guitar or monitor cable.  Much more elaborate cable testers are available at music stores, but they are fairly complex and are mostly useful to road crews and t __ Designed by Andrew R. Morris

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