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Testers / Instruments Circuits

1.2GHz Frequency Counter:

1.5 AMP   Shunt Ammeter Circuit: circuit converts a 0-15Volt voltmeter to a 1.5Amp ammeter

12 Volt Battery Capacity Tester: This circuits makes the amp-hour test simple and cheap. The amp-hour reading obtained should be accurate to within10% if the load resistor (lamp) is properly calibrated. 

120 MHz Frequency Counter:

16 Bit AD Converter W /  RS232 Interface:

2 Tone Audio Oscillator (use for SSB Tests):

220 Volt Live Wire in Wall Scanner 2:

220 Volt Live Wire in Wall Scanner: This circuit senses power lines behind walls 

220 Volt Wiring Detector:

25 k Volt Generator Tests Insulation: 06/04/98 EDN-Design Ideas

3 Channel Spectrum Analyzer: This3 channel15 LED spectrum analyzer can be used as an addition to any audio amp project. It produces fantastic displays on3-LED bars that can be individually adjusted for any particular frequency range.

4 Channel DSO for oscilloscope:

50 MHz Frequency Counter, Voltage Meter & SWR / PWR Indicator:

50 MHz Frequency Counter, Voltage Meter & SWR/PWR indicator:

555 Go / No Go Tester:

555 Timer IC Tester:

741 Based Light Sensor: CdS photocell used for light/dark controlled relay

AC Line Current Detector:

AC Millivoltmeter:

AC/DC LED Indicator:

Accelerometer Schematic:

AdjuStable Continuity Tester:

Adjustment Free Inclinometer operates on 2.7V: 04/24/97 EDN-Design Ideas 

ADXL202 Accelerometer to C Volt Output: The Air Whammy is a simple dual control voltage generator that uses a 2 axis accellerometer as the source. The whole circuit fits into a small project box (approximately 65x40mm), and is powered from a 12V AC plugpack. 

Air Pressure: Circuit uses a NPP301 pressure sensor. Range of this sensor is1bar (15psi). It will output40mV at normal air pressure and3x overload doesnt damage the device.  


Analog input circuit serves any microcontroller: 12/20/2001 EDN - Design Ideas / The simple ADC in Figure 1 is perfect for getting analog signals into a purely digital microcontroller. Using just five surface-mount parts, you can assemble it for less than 50 cents (1000), which is approximately half the cost of a single-chip-ADC approach in the same volume. Moreover, this design takes only one pin from the microcontroller to operate. .

Analog LED Bar VU Meter: built around discrete components  

Arbitrary Waveform Generator:

Audible Circuit Tracer:

Audible Continuity Tester:

Audio Frequency Meter:

Audio LED VU Meter: built around discrete components  

Audio MilliVoltmeter:

Audio Test Oscillator:

Audio test Station:

Battery Equal Charge Indicator:

Battery Pack Discharger:

Battery Tester for 1.5 & 9V:

Beeper to Find Short Circuits:

Build a Magnetic Field Immunity Tester:

Build your own bypass capacitor tester: 12/06/2001 EDN - Design Ideas / Most circuits use bypass capacitors and can deliver substandard performance if the capacitors have poor pulse characteristics. Few if any articles cover how to test bypass capacitors for pulse characteristics. The circuit in Figure 1 tests these characteristics. It charges the capacitor under test through 100 kU for approximately 1 msec and then discharges it through 10U for a... .

Cable Tester is Fast & Cheap: 09/24/98 EDN-Design Ideas 

Calibrate scope jitter using a transmission line loop: 09/20/2001 EDN - Design Ideas / Digital-clock-period jitter is the variation in the period of a clock cycle compared with a nominal (average of many cycles) clock period. To accurately measure period jitter using an oscilloscope, you must subtract the oscilloscope jitter fro.

Calibration Technique uses Sound: 09/01/98 EDN-Design Ideas 

Capacitance Meter:

Cell Cycler Sorting Sires Superior Batteries: 06/23/94 EDN-Design Ideas

Circuit Adapts Signals for Visual Perception: 10/12/95 EDN-Design Ideas 

Circuit measures currents in dc servo motor: 12/06/2001 EDN - Design Ideas / The simple circuit design in Figure 1 lets you measure all components of a current flowing in a dc servo motor. The rectified output of the circuit uses ground as a reference, so you can measure the output by using a single-ended A/D converter. The current-sense resistor, R1, has a value of 0. .

Circuit Measures Small Currents Referenced to High Voltage Rails: 01/07/02 EDN-Design Ideas / / PDF contains multiple circuits - scroll to find this circuit

Circuit Monitors Multiple Contact Closures: 02/15/96 EDN-Design Ideas 

Circuit Monitors Pump On/Off Times To Ensure Safe Operation : Electronic Design - Ideas for Design / In a septic-tank-based sewage system, waste water and toilet wastes from, say, a residence drain into the first compartment of a two-compartment septic tank. A grating between the compartments allows just liquid waste to drain into the second...  

Circuit Provides Accurate RTD Measurements: 04/12/01 EDN-Design Ideas / PDF contains multiple circuits - scroll to find this circuit.

Circuit Tests Power Outage Susceptibility: 03/03/97  EDN-Design Ideas 

Circuitry for inexpensive Relative Humidity Measurement: National Semiconductor Application Notes,04-Nov-1995 

Connection Tester:

Constant Voltage Load Tests Battery Chargers: 04/11/96 EDN-Design Ideas 

Construction of Low Resistance Shunts:

Continuity Tester, Latching: Awesome tester!- at least in the designers opinion! 

Continuity Tester, Smart:

Continuity Tester:

Convert your DMM to a pH meter: 10/17/2002  EDN - Design Ideas / It's often necessary to know the acidity of a solution to control a process. Even inexpensive pH meters can be relatively costly, and many of the inexpensive models have no output that you can readily connect to a computer interface. A simple solution to this problem is to attach a pH probe to a high-impedance input of an op amp and read the output with a digital voltmeter (Figure 1)..

Create your Own Meter:

Curious C Beeper:

Current Sense Amplifier Handles High Voltages: 11/06/97 EDN-Design Ideas

Current Sense IC Prevents Overcurrent Damage: 04/25/96 EDN-Design Ideas 

Cut Phone Line Detector #1: Can be used to alarm security system 

DC Millivolt Meter:

Deflection Amplifier for oscilloscopes:

Delay Simulator Debugs Communications Equipment: 10/27/95 EDN-Design Ideas

Design makes handy audible circuit tracer: 01/09/03  EDN-Design Ideas / The circuit tracer in Figure 1 is a handy tool for finding connectivity paths on a pc board. Because the sense voltage you use to measure the path is lower than a transistor's VBE voltage, you can use the design in circuits containing semiconductor elements without affecting the measurement. The tracer's output takes the form of audio tones

Differential Scope Probe Delivers 6GHz Bandwidth to the Screen: 02/20/03 EDN-Design Ideas /  PDF contains multiple circuits - scroll to find this circuit

Digital / Standard Phone Line Tester: make sure that the line is suitable for modem use and your PCMCIA does not damage if you plug it in

Digital Frequency Counter:

Digital PC Oscilloscope:

Digital Pressure Gauge:

Digital Volt Meter With Video Output:

Digital Volt Meter:

DIGITAL VOLTMETER: This is just a schematic view of a digital voltmeter all components and values are listed.

Diode & LED Tester:

Dip Oscillator for HF:

Distortion Analyzer:

Distortion Measurement Circuit:

DMM Measures Light Level #1: 07/04/94 EDN-Design Ideas 

DMM Measures Light Level #2: 08/15/96  EDN-Design Ideas 

DSPbased Wireless Analyzer Targets 2.5 and 3G Networks: 02/20/03 EDN-Design Ideas /  PDF contains multiple circuits - scroll to find this circuit

Electric Field & Leakage Detector:

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.

Electromagnetic Field Probe With Meter:

Electronic Construction Level:


Eliminate thermoelectric EMF in low ohm measurements: 06/13/2002  EDN - Design Ideas /    When two different-metal conductors connect together in a loop and one of the junctions is at a higher temperature than the other, an electrical current flows through the loop. The magnitude of this current depends on the type of metals involved and the temperature differential of the junctions. When you open such a loop, a thermoelectric voltage appears across the open ends..

EMF Field Probe:

ESD Gun :

ESR Meter:

Ethernet 10Base T Simulator Jig yields Zero Emissions: 10/22/98 EDN-Design Ideas 

Expanded scale indicator revisited: 08/08/2002  EDN - Design Ideas / The visualization aid that a previous Design Idea describes allows only the expansion of the upper end of the scale (Reference 1). But what can you do if, according to your project requirements, you need to expand the middle region of the scale? Figure 1a illustrates the challenge. A voltmeter comprises a 100-�A dc meter and a series resistor

Expanded Scale Voltmeter uses Just Two Parts: 01/20/1994 EDN Design Ideas / The expanded voltmeter doesnt require trimpots to obtain usable accuracy or require the tedious selection of Zener diodes. This circuit consists of only two parts and a5V meter. The circuit is completely linear and requires no calibration except the rare mechanical zeroing of the meter. By using a split voltage reference system with floating output, the zero point of the voltage supplied to the meter equals the absolute sum of the two references.  

Femto Capacitance Meter: This meter measures into the low femtofarad area. Measuring in the femto area allows the smallest capacitors to be measured with precision. Such capacitors are commonly used to compensate for input and stray capacitance in amplifiers.

Field Strength Meter #1:

Field Strength Meter #2:

Field Strength Meter #3:

Fluxmeter to DVM input:

Four Channel Oscilloscope Adapter:

Frequency & Capacitance Meter:

Frequency Comparator Draws 8 �A: 03/03/97  EDN-Design Ideas 

Frequency Comparator has Status Output: 12/26/02 EDN-Design Ideas  / The original application for the circuit was to check the number of revolutions of an engine with only one LED as an indicator. The measurement of the number of revolutions usually involves sensors with a frequency output proportional to the number of revolutions.

Frequency Comparator:

Frequency Counter Module:

Frequency Doubler operates on Triangle Waves: 09/29/94 EDN-Design Ideas 

Frequency Measurements using PC:

Frequency Window Comparator has hysteresis: 11/07/96  EDN-Design Ideas 

Full Featured Transistor Tester:

Function Generator:

Function Generator:

Grid Dip Meter:

High / Low indicator:

High Side Current Sensor has Period Output #2: Maxim APP 1084: May 31, 2002

High side current sensor has period output: 03/07/2002  EDN - Design Ideas / You use high-side current monitoring in many battery-powered products that require accurate monitoring of load current, charger current, or both. In applications for nonportable designs, high-side-current monitoring serves as a power-supply watchdog that can flag a failure in downstream devices. .

High side current sensor monitors negative rail: 04/17/03  EDN-Design Ideas / All dedicated current-sense amplifiers provide high-side sensing on a positive supply, but you can adapt such circuits for monitoring a negative supply (Figure 1). The positive-supply pin, V+, connects to the system's positive supply, and the ground pin, GND, connects to the negative supply, VEE. That arrangement monitors the negative supply and provides a positive output voltage for the extern..

HighVoltage Monitor Features High Accuracy : 08/1902 Electronic Design - Ideas for Design / Many applications call for measuring ac lines or high dc voltages. One common technique uses a large voltage divider followed by a buffer. Another employs an inverting attenuator. The problems associated with both methods stem from uneven power...  

Improve Voltage Readings By Doubling a DVM's Scale : 04/29/02 Electronic Design - Ideas for Design / The ubiquitous, and now inexpensive, 1999-digit digital panel meter or digital voltage meter (DVM) module is a very useful addition to the range of test and display gear currently available. It's accurate, robust, and easily scaled for ranges from...  

In Circuit Electrolytic Tester:


Indicator features expanded scale: 02/21/2002  EDN - Design Ideas / Test equipment for a production line should be user-friendly (read "idiot-proof") and should offer minimal test time. In many cases, the test fixture must give an operator only one answer: pass or fail. Usually, two indicators assume this role: green for pass and red for fail. In most applications, a sensor transforms the tested parameter to a voltage; the test fixture must measure this v... .

Indicator has Expanded Scale: 02/21/02 EDN-Design Ideas  / PDF contains multiple circuits - scroll to find the one of interest 

Inductance meter : for 0.5 uH to 50 uh RF inductors, displays on digital voltmeter

Inductance Meter:

Inductive Pickup: simple device for detecting audio-frequency electromagnetic signals, such as those emanating from a loudspeaker, or its cable  

Infrared Remote Control Tester #1: measures the relative intensities of different Infrared light sources  

Infrared Remote Control Tester:

Integrator Forms Picoammeter: 07/17/97 EDN-Design Ideas 

Ion Detector:

Isolated, 12bit, 8 Channel, a / D Converter With PC Interface & 0.1% Accuracy:

LCD Frequency Counter (PIC16F84):

LED Audio VU Meter: logarithmic scale with3 dB steps, based in LM3915 IC  

LEDBarograph Driver:

Light Meter:

Light Pollution Meter : LED brightness control circuit and a multimeter to compare light levels to LED level.

Light Sensor Adapter for Oscilloscope:

Lightening Detector:

Line Output / Flyback Transformer tester:

Linearized RF Detector:

Live Power Line Detector:

Load Pulser Tests Supply's Transient Response: 04/11/96 EDN-Design Ideas

Load Simulator Maintains Constant Power: 04/11/96 EDN-Design Ideas    

Logic Analyzer:

Logic ChipTester:

Logic Probe #1:

Logic Probe #2: with probe

Logic Probe #3: with probe, CMOS

Logic Probe With Pulse, CMOS:

Logic Probe With Pulse:

Low cost anemometer fights dust: 08/30/2001 EDN - Design Ideas /  As higher levels of power dissipation underscore the need for cooling, more and more fans are finding their way into small electronic enclosures. The dust that fans pull into these enclosures can, however, cause major problems for high-reliability systems. By coating heat sinks and electrically charged components, the dust acts as a blanket that raises the effective thermal impedance betw... .

Low Cost Dot/bar Generator:

Low cost relative humidity transmitter uses single logic IC: 11/08/2001 EDN - Design Ideas /   The low-cost percentage-relative-humidity radio transmitter in Figure 1 operates in a cold-storage warehouse for vegetable storage at temperatures of 1 to 5 C. It is generally difficult to collect such data from a low-temperature area with high humidity and low illumination. The transmitter design is simple: It uses a readily available, capacitor-type percentage-relative-humidity se... .

Low Tech DCC Meters:

Machine Vibration Activates Hour Meter: 01/16/97 EDN-Design Ideas


Make a Simple PC based Frequency Meter: 04/29/99 EDN-Design Ideas / PDF contains multiple circuits - scroll to find this circuit

Making Differential Probes: for sensing audio signal voltages across devices that are not ground referenced  

Measure humidity and temperature on one TTL line: 08/30/2001 EDN - Design Ideas /  By combining the responses of an Analog Devices (www.analog.com) AD590 temperature sensor and a Humirel (www.humirel.com) HS1101 humidity sensor, you can generate a single TTL-level signal containing information from both sensors (Figure 1). This design uses a 74HC123 monostable multivibrator, IC1, to form a free-running oscillator. .

Measure Inductance With DC Superimposed: 07/06/95 EDN-Design Ideas 

Measure open circuited cables using a multimeter: 09/26/2002  EDN - Design Ideas / You can use a multimeter with capacitance-measurement capability to measure the length of wire or cable to an open circuit. The capacitance of a pair of wires (or a wire to a shield) is directly proportional to the length of the wire. If you know th.

Measuring RF Voltages with a VOM:

Method simplifies testing high Q devices: 02/21/2002  EDN - Design Ideas / The design of low-phase-noise oscillators requires careful attention to resonator unloaded Q. In the construction of a low-phase-noise, high-frequency oscillator, the goal is to achieve an unloaded-Q figure greater than 400 in a reasonable package. Also, you need to monitor the effect of the package and pc-board arrangement. .

Micro Ohm Meter:

Micro Volt Probe:

Microphone Circuit Test Oscillator: 440 Hz Tone generator for testing XLR microph1-lines  

Microphone Polarity Tester: