Electrical and Electronics meters and tester project and equipment

AC Current Probe for Oscilloscopes
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.
http://cappels.org/dproj/aciprobe/ACCurrentProbe.html



Beat Balance Metal Detector
The frequencies of the two oscillators are then mixed in similar fashion to BFO, to produce an audible heterodyne. On the surface of it, this design would seem to represent little more than a twinned BFO metal detector.
http://www.zen22142.zen.co.uk/Circuits/Testgear/bbmd.htm


Femto Capacitance Meter
Contents: Triangle Wave Generator, Current-to-Voltage Converters, Peak Detector, Measuring Large Capacitors.
http://nov55.com/cap/cap1.htm


Solar Panel Current Meter
It has very low power loss for currents in the 0-10A range. It also works as a general purpose DC current meter. The circuit can be used on either the positive or negative side of a DC circuit.
http://www.solorb.com/elect/solarcirc/imeter/index.html



DC Voltmeter with high impedance
A instrument should be set so that the pointer rests just below zero on the scale. The unit is then switched on and with the input shorted, TR1 is adjusted until an exact zero indication is obtained.
http://users.otenet.gr/~athsam/dc_voltmeter.htm


Digital Volt and Ampere meter
http://users.otenet.gr/~athsam/digital_volt_and_ambere_meter_gr.htm


EVB ESR meter
It has big protection diodes in parallel with the test leads (you can't measure battery ESR.
http://members.ozemail.com.au/~bobpar/esrmeter.htm


3-digit frequencymeter
Designed is based on a old well known Fairchild Semiconductor counter IC, the MM74C925. It's basically a 4-digit counter with seven segment-decoder & multiplexer and counter & latch registers.
http://www.turbokeu.com/myprojects/flowmeter.htm



Build your own Gaussmeter
Voltmeters are fairly inexpensive and easy to find, but where do you purchase a Gaussmeter (also known as a magnetometer).  I built a hand-held Gaussmeter for measuring the polarity and strength of a magnetic field.
http://my.execpc.com/~rhoadley/magmeter.htm



LED Audio VU Meter
Is simpler and smaller than it's analogue counterpart, and is very common in audio equipment. This version is based on a National Semiconductor IC, and uses the logarithmic version. Each LED operates with a 3dB difference from the previous one, and a jumper is provided to allow dot or bar mode.
http://sound.westhost.com/project60.htm


Light Pollution Meter
The design and construction of a visual comparison photometer for measuring sky brightness and light pollution.
http://avery.home.mindspring.com/LPmeter.htm

PC-BASED OSCILLOSCOPE
This circuit conditions different signals of frequency below 1 kHz and displays their waveforms on the PC’s screen. The hardware is used to condition the input waveform and convert it to the digital format for interfacing to the PC. The software for acquiring the data into the PC and displaying the same on its screen is written in Turbo C.
http://www.electronicsforu.com/efylinux/circuit/dec2002/circuit1_oscilloscope.pdf



Digital potentiometer
The potentiometer portion of a mixed-signal, digitally programmable potentiometer adds variability
to an analog circuit, and its digital controls provide programmability. You can use a digital potentiometer in two ways in an analog circuit.
http://www.edn.com/filtered/pdfs/contents/images/53002di.pdf



VU And PPM Audio Metering
used to be the mainstay of audio metering systems, but they have been replaced by LED metering in a great many mixers and other applications. Even in software, the most common level meter is made to look like an LED meter.
http://sound.westhost.com/project55.htm



Tachometer/Speed Switch Building
Frequency to voltage converters are available in a number of forms from a number of sources, but invariably require significant additional components before they can be put to use in a given situation.
http://www.national.com/an/AN/AN-162.pdf


True RMS Watt Meter
This circuit will give you a good, Accurate Watt Meter that can measure various power levels.
In the Origional Article the Shunt was a .001 Ohm Copper Shunt giving a 1000 Watt Scale.
http://www3.telus.net/chemelec/Projects/Watt-Meter/Watt-Meter.htm



TRANSISTOR TESTER & SIGNAL INJECTOR
All you have to do is fit the three leads of a transistor to the tester in any order and the LEDs will let you know the base and if the transistor is NPN or PNP. Section 3 will identify the collector and emitter leads and provide an indication of the gain of the transistor.
http://www.talkingelectronics.com/html/Combo-2.html


Alternative test patterns
A Windows’ program is supplied with the generator that will encode a suitable image file and upload it to the generator, creating signals in all of the common TV standards.
http://www.barney-wol.net/testpatterns/testpatterns.html


High Precision Volt Meter
http://www.triplespark.net/elec/analysis/HiPVM/


Digitalt Wattmeter
http://www.webx.dk/oz2cpu/radios/milliwatt-dk.htm

Universal High Resistance Voltmeter
The full scale deflection of the universal high input resistance voltmeter circuits.
http://www.electronicsforu.com/efylinux/circuit/feb2003/feb00_universal.pdf


Ultrasonic Range Meter
he way of measuring measures the time which the ultrasonic returns from the measurement object. The about 10-m distance can be measured by adjusting the resistance value of the inner circuit.
http://hobby_elec.piclist.com/e_srm.htm