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Tester or Measurement (Instrument) Circuits

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Last Updated: November 22, 2021 03:00 PM
Circuits Designed by Dave Johnson, P.E. :

Resistance Tester got UL Ground Requirement -  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. . . Circuit by David Johnson P.E.-April, 2001

RFID Test Circuit -  I designed this test the concept of using light techniques to send identification data instead of RF. . . . Hobby Circuit designed by David A. Johnson P.E.-February, 2002

RS232 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 Johnson P.E.-December, 2007

RS-232 Serial Interface Status Indicator Circuit -  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 volts.  Two dual color LEDs are used as indicator lights . . . Hobby Circuit designed by David A. Johnson P.E.-December, 2007

Capacitance Proximity Switch
Draws very low power - Ideal for battery-powered applications
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Links to electronic circuits, electronic schematics and designs for engineers, hobbyists, students & inventors:

Remote Telltale for Garage Doors -  if you have a perfect memory you won't need this.  But the rest of us could find it very handy!  it lets you know if you've left the garage door open without stumbling out in the dark or the pouring rain...__ SiliconChip

Remote Temp Sensor Needs No Power Supply -  12/21/95 EDN Design Ideas:  Measuring temperature at a remote location is a common requirement, but the implementation is usually not straightforward.  Most temperature sensors have a voltage or current output, which, to minimize noise pickup, should undergo conversion to digital form near the sensor.  Thus, an ADC, a digital interface, and a power supply must all be situated at the temperature-measurement point.  The circuit in Figure 1 monitors the temperature at a remote location and transmits that temperature to a host computer. Design by Wes Freeman, Analog Devices Inc  Santa Clara, CA

Remote Thermometer -  This circuit is intended for precision centigrade temperature measurement, with a transmitter section converting to frequency the sensor's output voltage, which is proportional to the measured temperature.  The output frequency bursts are conveyed into the mains supply cables.  The receiver section counts the bursts coming from mains supply and shows the counting on three 7-segment LED displays.  The least significant digit displays tenths of degree and then a 00.0 to 99.9 °C range is obtained.  Transmitter-receiver distance can reach hundred meters, provided both units are connected to the mains supply within the control of the same light-meter.   __ Contact Flavio Dellepiane, fladello @ tin.it

Remote Watering System -  This remotely controlled watering system is both inexpensive and easy to expand.  it is designed to operate in conjunction with a conventional watering timer and allows remote switching between nine zones.  The prototype is used in a bore system, where a deep-well pump must be started and kept running while zones are being changed.  This is necessary to minimise cycling and results in maximum pump life.  A standard portable telephone is used as the transmitter and receiver__ Learning Electronics

Replace a rotary switch with a potentiometer -  EDN Design Ideas:  04/07/2014     Why use an expensive rotary switch with your microcontroller when you can use a cheap pot instead? Design by Claude Haridge

Resistance Calculator Yields Precise Values -  08/03/95 EDN Design Ideas:  For times when the nearest preferred resistor value isn't close enough to the desired value, a program comes in handy. (You'll find the executable ZiPfile and several source-code files for the program in EDN BBS /Di_SiG #1740.) The program finds all combinations of two series or parallel connected resistors, within a specified tolerance of the required value, using only preferred values from the E6, E12, E24, and E96 ranges (6, 12, 24, and 96 different values per decade).    Design by David Kirkby, Department of Medical Physics, University College London, London, UK

Resistance Measurement using Sample & Hold Method -  A sample and hold circuit, as the name implies, samples an analogue input signal and holds its value until the input is again sampled.Fig.1 shows the basic principle of the...__ Electronics Projects for You

Resistance Tester got UL Ground Requirement -  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. . . Circuit by David Johnson P.E.-April, 2001

Resolve 0.1-Ff Change from 100 Pf -  01/06/00  EDN Design Ideas:  The circuit in Figure 1 can resolve 0.1-fF changes in a 100-pF bridge element and can accommodate large-scale changes in the bridge without adjustment.  You can use changes in capacitance to measure applied pressure, rotation, torque, liquid level, the wat Design by Derek Redmayne

Return Loss Bridge -  Another of the tasks that I wanted to perform on the newly designed 2N2/20 was to characterize the input impedance of the receive strip, and the output impedance of the transmit strip.  This Return Loss Bridge was built for that purpose.  The design comes directly out of "Experimental Methods in RF Design" by Wes Hayward, W7ZOI et.  al., figure 7.41 on page 7.23.  it works exactly as described. __ Designed by Jim Kortge, K8IQY

Rev Counter -  a 10-led rev counter/tachometer using the lm2917.  Also a general purpose frequency-voltage circuit __ Contact P. Townshend - EduTek Ltd

Revolution Meter -  Revolution meter by measuring method of strobe synchronization.  it can measure up to 100, 000 rpm in two ranges.   __ Designed by The Electronic Lives Manufacturing-presented Chan

RF Detectors, level meters, attenuators, dummy loads, signal dividers -  several circuits on this page.   __ Designed by Jan-Martin Nøding

RF Field Strength Indicator -  Useful as a transmitter tune-up meter or an RF sniffer, this is an RF field strength indicator that is loosely based on the Broad Band RF Field Strength Probe, described elsewhere.  it detects RF via a square law detector, basically its a crystal set with gain.  The bias circuit for the detector is significantly modified from the probe to reduce the effects of battery voltage droop during use.   __ Designed by Dick Cappels

RF Field Strength Probe -  This broadband probe has a small antenna (about a 15 cm length of insulated wire).  Radio Frequency energy coupled to the antenna is detected and made available to drive millivolt level signals to the input of a DVM (Digital Volt Meter).  its battery powered for convenience with very low current drain and automatic shutdown for long battery life.   __ Designed by Dick Cappels

RF Inductance Meter -  needed a way to measure hand-wound RF inductors in my second lab, and since I would only be doing this occasionally, I didn't need anything fancy, and since once a friend finishes his AT90S1200-based design, I plan to make one myself, I figured I'duse this for less than a year, so I didn't want to invest __ Designed by Dick Cappels

RF Isolator Uses Differential Amplifiers -  An RF isolator is a seemingly magic device that allows signals to pass in only one direction.  Signals applied to the input port are sent to the test port and signals coming into the test port can only go to the output port.  This one-way property is usually accomplished with special non-linear ferrite/magnet structures operating at very high frequencies.  Fig.1 shows an active RF isolator __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

RF Power Calibrator -  Schematic only __ Designed by va3iul

RF Power Meter -  Many beginners trying out their skill with QRP TX, for the first time have to overcome many problems before they are able to come on the air.  On usual complaint is that, every thing is working fine but the signal is not going out.  Here is a simple set up which will enable them to measure the out put power of their transmitter.  All that they require is a good multimeter which has a sensitivety of 20k ohms/4 Watts which is adequate for low power transmitters.  The 8k resistor should be kept close to the out put terminal of the transmitter__ 

RF Power meter / dummy load -  A 50 Ohm dummyload is an essential part for any radioamateur as is a powermeter.  The prices of such relative simple equipment is expensive, but not for us handy Hams Hi.  All you need is a metal box (or plastic box painted inside with graphite or other conducting/RF-shielding capable material) , a few resistors and basic components (which can be salvaged from old radio's, switching power supplies etc.  .) and a analog meter.  I used a Radio-shack meter, but any (sensitive) meter can be used.  it's all a matter of calibrating your meter correctly, which is easy if you can lend a good commercial RF power meter.   __ Designed by Guy Roels ON6MU

RF Power Meter for QRPers -  Here is a simple set up which will enable them to measure the out put power of their transmitter. All that they require is a good multimeter which has a sensitivity of 20k ohms/4 Watts which is adequate for low power transmitters.__ 

RF Power Meter for the QRPer -  amateur radio construction projects.   __ Designed by Peter Parker

RF signal-and power generators -  several circuits on this page.   __ Designed by Jan-Martin Nøding

RF sniffer finds 2.4-GHz sources -  11/23/06  EDN Design Ideas:  Locate interference sources in the iSM band Design by Vladimir Dvorkin, Linear Technology Corp, Milpitas, CA

RF Sweeper-VK2ZAY -  Schematic only __ Designed by va3iul

RFID Test Circuit -  I designed this test the concept of using light techniques to send identification data instead of RF. . . . Hobby Circuit designed by David A. Johnson P.E.-February, 2002

Ridiculously Sensitive Electric Charge Detector -  This simple circuit can detect the invisible fields of voltage which surround all electrified objects.  it acts as an electronic "electroscope.  "  __ Designed by William J. Beaty

Ring Oscillator Measures Cable Length -  05/12/94 EDN Design Ideas:  in Fig 1, an ECL exclusive-NOR gate (F100107] and a length of cable form a simple ring oscillator.  The delay from the cable and the gate determine the ring oscillator’s frequency.  A 100m cable yields approximately a 600-MHz oscillation frequency.  The gate’s second output connects to a frequency counter.   Design by B Enning, Institut für Nachrichtentechnik, Flensburg, Germany

RJ45 Cable Tester -  Described here is a simple RJ45 cable tester circuit which can be used for testing the RJ45 network cables.  The circuit can check both straight-through and crossover-type RJ45 network cables....__ Electronics Projects for You

RMS Output Is Linearly Proportional to Temperature Over Wide Range -  01/18/13  EDN Design Ideas:  it is known that the p-n diode can be the basis of an accurate thermometer for cryogenic temperatures up to about 200°C.  A constant current is maintained through the diode and the voltage across it gives an indication of the temperature.  The magnitude of Design by R.O. Ocaya, University of the Free State, Phuthaditjhaba, South Africa

RMS-to-DC Conversion Just Got Easy -  DN288 Design Notes__ Linear Technology/Analog Devices

RMS-To-DC Converter Is Accurate & Stable -  09/14/95 EDN Design Ideas:  Combining the well-known true rms-to-dc circuit with a simple S/H circuit eliminates offset errors, which increases accuracy and temperature stability.  The circuit in Fig 1 uses a low-cost analog multiplier, IC 1; an integrator, IC 3A, R5, and C1; and an analog inverter,  Design by Sergey Velichko, SCP, Boise, ID

Room heating controller -  Tired of mechanical thermostats that overshoot the set point and make you waste expensive energy? Here is a phase-control device that works well and is simple!  __ Designed by Manfred Mornhinweg

Room Noise Detector -  This circuit is intended to signal through a flashing LED, the exceeding of a fixed threshold in room noise, chosen from three fixed levels, namely 50, 70 & 85 dB. Two Op-amps provide the necessary circuit gain for sounds picked-up by a miniature electret microphone to drive a LED. With SW1 in the first position the circuit is off. Second, third and fourth positions power the circuit and set the input sensitivity threshold to 85, 70 & 50 dB respectively. __ Contact IQ Technologies

Room temperature controller -  On this page, I will introduce the room temperature controller with PIC .  This equipment uses two temperature sensors, drives external equipment, and keeps the temperature of the room at preset temperature.  The purpose of this equipment is for preventing room temperature going up with the heat of the computers.  Electric cost will become high if an air-conditioner is always operated.  Then, I made the equipment __ Designed by Seiichi Inoue

Rotary Controller Positions Stepping Motor -  EDN Design Ideas:  08/03/95    The circuit in Fig 1 uses a servo potentiometer, as opposed to a rotary switch or encoder, to provide the necessary drive pulses for a stepping motor.  This motor positions a pointer by the rotation of a manual control.  The circuit must be precise, allow a rapid response, and be simple to use. (This circuit was part of a complex apparatus used for a series of physiological tests.) Another requirement is that the control had to be a small, handheld, battery-operated device.    Design by TG Barnett and ME Rosenberg, Department of Physiology, Queen Mary and Westfield College, London, UK

Rotary Encoder Mates with Digital Potentiometer -  6-Mar-03 EDN Design Ideas:  Buck IC boosts battery voltage for white LED - in developing electronic systems, designers look for products or ideas that may benefit from the better performance, smaller size, lower cost, and improved reliability that an IC can offer.  Toward that end, the digital potentiometer emerged as an alternative to its mechanical counterpart, the mechanical potentiometer Design by Peter Khairolomour, Analog Devices, San Jose, CA

RPM Meter for Automobiles -  An efficient way to measure the RPM of a vehicle is through its ignition pulses.  RPM of a vehicle is directly proportional to the rate of its ignition pulses.  An ignition...__ Electronics Projects for You

RS 232 to TTL converter tests UARTs with a PC -  05/29/08  EDN Design Ideas:  A simple RS-232-to-TTL converter tests UARTs using a PC's serial port for power Design by Matthieu Bienvenüe, Malissard, France

RS232 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 Johnson P.E.-December, 2007

RS-232 line Monitor & loopback cables -  if you have problem with RS232 cabling, your best "emergency" tool may be a breakout box (sometimes called an LED box).  The normal units only come in the DB25 size, but with a couple of DB9 to DB25 adaptors, they can be used with DB9 cables as well.  The units have an LED for each signal line in the cable, and the LED lights green or red dependent on the signal state.  __ Airborn Electronics, Australia

RS-232 Serial Interface Status Indicator Circuit -  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 volts.  Two dual color LEDs are used as indicator lights . . . Hobby Circuit designed by David A. Johnson P.E.-December, 2007

RS-232/485 converter has automatic flow control -  04/12/01 EDN Design Ideas:  RS-485 communications can provide longer range and better noise immunity than RS-232, as well as multidrop capability.  Because it does not have separate transmit and receive lines, RS-485 requires flow controlPDF contains multiple circuits, scroll to find this circuit by John Howard, Kw Aware, Ventura, CA

RS-232C link Monitors animal activity -  11/06/97 EDN Design Ideas:  A common need in biological experimentation is the ability to unobtrusively monitor the activity of small caged animals, such as mice, rats, and rabbits, as they move about their enclosures.  This monitoring must be over long periods and around the clock.  The circuit in Design by W Stephen Woodward, University of North Carolina--Chapel Hill

RS-232C port measures pressure -  08/01/97  EDN Design Ideas:  A simple circuit and accompanying software turn a pressure sensor into an accurate and cheap pressure digitizer that works with any PC's RS-232C COM port.  Many manufacturers make micromachined silicon piezoresistive pressure sensors Design by W Stephen Woodward, University of North Carolina--Chapel Hill

RTD & Thermocouple Remote Temperature Digitizer -  The LTC2449 is commonly used with thermocouples and RTDs as shown in this circuit.  Thermocouple outputs produce very small changes (tens of microvolts per degree C) and the output will be negative if the thermocouple is colder than the cold junction connection from the thermocouple to the copper traces on the PCB.  The __ Linear Technology/Analog Devices App Notes, Mar 30th 2010

RTD Calculator -  Javascript program converts 100 ohm platinum resistance into temperature.   __ Designed by Jim Haggerman, Hagerman Technology LLC

RTDs Provide Differential Temperature Measurement -  12/31/69 EDN Design Ideas:  You sometimes need to measure the differential temperature between two points in a system to a greater accuracy than that required in measuring the absolute temperature at either of the individual points.  Differential-temperature measurement is necessary, for example, in monitoring heating-energy consumption in an apartment.  Hot water enters from one pipe, circulates around the apartment through the radiators, and exits through a second pipe.  Billing depends on the temperature differential between the entry and exit copper pipes, so absolute temperature is irrelevant.  One way of measuring is to attach an RTD (resistance-temperature detector)  Design by John Wynne, Analog Devices Inc, Limerick, Ireland

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

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