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Probe Circuits
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Last Updated: November 22, 2021 02:41 PM

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

1000:1 EHT Probe-  Do you need to measure the EHT voltage in a CRT-based scope, computer monitor or TV receiver, or perhaps in a photocopier, laser printer or microwave oven? You'll need an EHT probe to suit your digital multimeter (DMM) to do this and you'll find they are pretty pricey.  Not to worry though, because here's one you can build for less than $40.__ SiliconChip

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

A Simple Circuit RF Probe for your DVM-  This probe is configured to work with a DVM with the industry standard input impedance of 10 Megohm. __ Designed by VK5JST / VK5TR

AC Current Probe for Oscilloscope Use-  I needed several current probes when designing the deflection circuits and high voltage supply for a computer display monitor, and the lab in which I was consulting only had one current probe, which I shared with the other four engineers on the project.  We did not really have a budget for test equipment on that project.  Designing the deflection circuit included designing several inductors, a current transformer among them.  It was merely a small diversion to design and put together a couple of simple current probes so I could, for example.  simultaneously watch the base current and the collector current of switching transistors.  The probe described here was designed to be used over the range of several tens of Hz to a couple MHz with currents from a few tens of milliamps to about 10 amps peak-to-peak.  Formulae are given which will allow you to create a design suitable for your own applications. __ Designed by Dick Cappels

Aquarium Probe-  A number of environmental factors including light and temperature affect fish culture.  The temperature of water has profound effect because fish cannot breed above or below the critical temperature limits.  Temperature...__ Electronics Projects for You

Audible continuity Tester-  A logic tester with an audible indicator can be handy when troubleshooting or testing a crowded circuit board.  It allows you to keep your eyes on the circuit, rather than on a LED on the tester.  The project described in this article is just such a tester.  It provides an audible indication of the logic level of the signal presented to its input __ Designed by Tony van Roon  VA3AVR

Audible Logic Probe-  Using a conventional logic probe, it is difficult to determine what is happening at a point in a circuit above 50 Hz.  The human eye isn’t able to perceive the change...__ Electronics Projects for You

Audible Logic Probe-  The probe uses 2 IC's and a handful of components to indicate the state of the input on 3 LEDs while the piezo gives an audible indication of the state of the line.  The input is connected to two inverters in the 4049 IC.  The top one is held above mid-rail via the 1M trim pot while the bottom one is held below mid rail by the 1M/220k voltage divider __ Contact Collin Mitchell

Build 3-State Logic Probe -  For less than 10 bucks you can build a piece of test gear that you'll find is one of the handiest in your tool kit__ SiliconChip

CDV700 Geiger Counter Probe Rebuilding-  This article describes the process of rebuilding a Geiger counter probe from the Victoreen CDV700 Geiger counter.  The process of converting the hard-wired probe to a probe with a pluggable BNC connector is also described.  The probe from the model CDV700-6B is similar, but not identical, the socket is easier to access on that model. __ Designed by Forrest Cook

Designing RF Probe-  make yourself simple and highly useful RF probe.  An essential tool for every home brewer. __

Differential scope probe Delivers 6-GHz bandwidth to the screen-  02/20/03 EDN Design Ideas:  With digital scopes that offer 6-GHz bandwidth suddenly almost commonplace and with industry participants now recognizing differential signaling as all but essential for sending multigigahertz signals across pc boards and backpla Design by Dan Strassberg

Digital Storage Logic Probe-  It Interfaces to a Win98 PC to give you more flexibility than you ever thought possible.__ SiliconChip

Diode Serves as a Sensor for a Thermal Probe-  02/16/12  EDN Design Ideas:  A two-transistor thermal probe can be used to diagnose circuit problems, such as hot components and thermal runaway. Design by Raju Baddi, Tata Institute of Fundamental Research, Pune, India

Electromagnetic field Detector-  This circuit is sensitive to low frequency electromagnetic radiation and will detect for example hidden wiring or the field that encompasses a transformer.  Pickup is by a radial type inductor, used as a probe which responds well to low frequency changing magnetic and electric fields.  Ordinary headphones are used to for detection.  The field that surrounds a transformer is heard as a50 or 60Hz buzz.  __ Designed by Andy Collison

Electromagnetic Field Probe Version 2-  An electromagnetic field probe designed to detect changing electric and magnetic fields.  The probe has switchable gain, a frequency response up to 400kHz and independent audio and meter monitoring. __ Designed by Andy Collison

Electromagnetic Field Probe with Meter Output-  This tester is designed to locate stray electromagnetic ( EM) fields.  It will easily detect both audio and RF signals up to frequencies of around 100kHz.  Note, however that this circuit is NOT a metal detector, but will detect metal wiring if it conducting ac current.  Frequency response __ Designed by Andy Collison

EMF Probe Version 2-  An electromagnetic field probe designed to detect changing electric and magnetic fields.  The probe has switchable gain, a frequency response up to 400kHz and independent audio and meter monitoring. __ Designed by Andy Collison

EMF Probe with Meter-  This tester is designed to locate stray electromagnetic ( EM) fields.  It will easily detect both audio and RF signals up to frequencies of around 100kHz.  Note, however that this circuit is NOT a metal detector, but will detect metal wiring if it conducting ac current.  Frequency response __ Designed by Andy Collison

Facilitate oscilloscope Debug of small microcontroller systems-  07/07/14 EDN Design Ideas:  A probe-to-the-metal approach is often the best way to debug a small µC system, and here’s some code to help out.  If you develop an application on a small microcontroller, your diagnostic tools for debugging of the program code might be very limited.  This Design Idea introduces a simple debugging routine for plotting the binary value of one byte on a scope display.  It uses one output pin of the microcontroller. Design by Josef Valasek

High-Impedance FET probe extends RF-spectrum analyzer's usable range-  21-Jul-05 EDN Design Ideas:  Op amp and careful design/construction build high-impedance RF probe Design by Steve Hageman, Windsor, CA

IC & DMM form direct-read-out temperature probe-  09/01/06 EDN Design Ideas:  Simple circuit yields linear voltage-versus-temperature output Design by Alfredo H Saab and Bich Pham, Maxim Integrated Products Inc, Sunnyvale CA

In-Situ Battery Test Probe-  This item describes a simple probe that allows in-situ AA and AAA battery voltage and current drain measurements without removing the cells from the holder.  In use, the probe is simply pushed between the positive end of one cell and either the negative end of the adjacent cell or the battery holder terminal.  The probe […]__

Isolated Probe-  PIC Project  Working on live telephone circuits can be a problem.  You just can't connect a normal scope probe to the circuit while it is tied to the phone line __ Designed by Luhan Monat - Mesa Arizona

Logic Probe-  An useful and easy to build Logic Probe with Pulse injector.  An schematic of a "digital version" is included. __ Designed by Jose Pino

Logic probe-  This logic probe uses a single CMOS IC and shows three logic conditions, High, Low and Pulsing.  In addition if the probe input is neither hi or low ( the high impedance state of tri-output logic IC's) then no LEDs will light.  Power from the logic probe is taken from the logic circuit __ Designed by Andy Collison

Logic Probe MkIIB-  The probe uses 2 IC's and a handful of components to indicate the state of the input on 3 LEDs while the piezo gives an audible indication of the state of the line.  The input is connected to two inverters in the 4049 IC.  The top one is held above mid-rail via the 1M trim pot while the bottom one is held below mid rail by the 1M/220k voltage divider __ Contact Collin Mitchell

Logic Probe uses Bicolor LED-  03/13/98 EDN Ideas - (   FILE has several circuits, scroll to this one) A project posed the challenge of replacing existing analog potentiometers (used to set brightness and contrast levels]in video monitors with digitally controlled potentiometers.  The different brands and models of monitors presented widely varying voltages across the potentiometers.  The design. Design by Mark Shill, Burr-Brown Corp, Tucson, AZ

Logic Probe Uses Six Transistors-  12/15/10 EDN Design Ideas:  Build a logic probe from discrete components. [Design Ideas by Raju R Baddi, Raman Research Institute, Bangalore, India Design by Raju R Baddi, Raman Research Institute, Bangalore, India

Logic Probe Uses Two Comparators-  EDN-Design Ideas -- 08/25/11  Build a logic probe whose voltage thresholds vary with your circuit's power supply voltage.  Measurement instruments must not affect the circuits they’re measuring.  A logic probe, for example, must correctly detect logic levels, and it must place no undue loads on the test circuit.  The logic probe must set thresholds on automatically checking logic levels, depending on the supply voltages of the ICs it is checking.  It should also not cause the checking circuit to function incorrectly. Design by Vladimir Rentyuk, Zaporozhye, Ukraine

Logic probe with integral pulser function-  This project is a combination Logic Probe and Logic Pulser.  It is capable of testing all sorts of digital and microcomputer projects.  You will find it extremely handy when designing a project as the golden rule is to test everything in steps and stages during the design-and-construction process. __ Designed by Collin Mitchell

Logic Probe1 with pulse TTL/CMOS -  One of the most frustrating problems with experimenting is not be able to check the logic state of TTL or CMOS ic's without the use of a triggered oscilloscope. The schematic diagram above shows a simple and inexpensive way of building a 'Logic Probe' yourself. It will provide you with three visible indicators; "Logic 1" ( +, red led) , "Logic 0" ( -, green led) , and "Pulse" ( yellow led) __ Designed by Tony van Roon  VA3AVR

Logic Probe2  with pulse TTL/CMOS -  This circuit uses the four 2 input NOR gates contained within the 4001 CMOS IC, and is primarily intended for testing CMOS circuits.  The probe derives its power from the supply of the circuit being tested.  The first gate, N1, has its inputs tied together so that it operates as an inverter, and it is biased by R1 so that roughly half the supply potential appears at its output __ Designed by Tony van Roon  VA3AVR

Logic Probe3 Audible TTL/CMOS -  A logic tester with an audible indicator can be handy when troubleshooting or testing a crowded circuit board.  It allows you to keep your eyes on the circuit, rather than on a LED on the tester.  The project described in this article is just such a tester.  It provides an audible indication of the logic level of the signal presented to its input __ Designed by Tony van Roon  VA3AVR

LOPIC Logic Probe with Pulser-  This project is a combination Logic Probe and Logic Pulser.  It is capable of testing all sorts of digital and microcomputer projects.  You will find it extremely handy when designing a project as the golden rule is to test everything in steps and stages during the design-and-construction process.  If you are not sure how a Logic Probe or Pulser works__

Low Capacitance Scope Probe Adapter-  An adapter to allow low capacitance probing of high frequency circuits. __ Designed by Dick Cappels

Low Cost Dual Channel Active AC Analog Probe-  Introduction When we are experimenting with AM receivers for LW, MW and SW we are in need of high impedance analog probe with low input capacitance, e.g.  well below 20pF.The required input...__ Electronics Projects for You

Low-Component-Count Logic Probe Works with TTL & CMOS Logic-  04/07/11  EDN Design Ideas: LEDs indicate logic levels.  The circuit in Figure 1 uses the LM358 dual op amp running as a comparator, plus a few other inexpensive components, to make a TTL (transistor-transistor-logic) /CMOS -logic probe.  The circuit gets its power from the circuit under test, which lets it work with TTL or CMOS logic.  The IC1A and IC1B op amps come in an LM358 package.  Switch S1 selects the TTL or the CMOS mode of operation.  The green LED shows logic low, and the red LED shows logic high. Design by Aruna Rubasinghe

LTD-Low Cost Telemetering Device-  The ATmega8 microcontroller-based Low-Cost Telemetry Device ( LTD) is an efficient telemetry keyer.  The LTD measures the voltage levels of up to four analog channels via its on-chip 10-bit ADC, converts the measurements to numbers, and then sends the data in Morse code to an external transmitter and to an attached RS-232 terminal.  It can be set up either by the RS-232 terminal, in which case, a character string, such as transmitter ID, can be sent, or it can be set up with only jumpers to ground.  Parts count is very low, in part because the ATMega8's internal clock is used for timing.  Jeff Heidbrier came up with the idea for this project, built the prototype, and collaborated with me on the design of the LTD and this documentation. 
 __ Designed by Dick Cappels


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