Testers / Instruments Circuits
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/DC LED Indicator:
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
accelerometer 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 doesn't 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:
Audio Frequency Meter:
Audio LED VU Meter: built around discrete components
Battery Equal Charge Indicator:
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
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
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:
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
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 VOLTMETER: This is just a schematic view of a digital voltmeter all components and values are listed.
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..
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-µA 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 #3:
Four Channel Oscilloscope Adapter:
Frequency & Capacitance Meter:
Frequency Comparator Draws 8 µA: 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 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:
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
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
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
Light Pollution Meter : LED brightness control circuit and a multimeter to compare light levels to LED level.
Light Sensor Adapter for Oscilloscope:
Line Output / Flyback Transformer tester:
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 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 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... .
Machine Vibration Activates Hour Meter: 01/16/97 EDN-Design Ideas
Magnetometer:
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
Mini DDS (Direct Digital Synthesis):
Mini DDS (direct Digital Synthesizer):
Modified Scope Probe Tests SurfaceMount Assemblies: 09/25/97 EDN-Design Ideas
MOSFET Current Sensing: Method of mirror current sensing a MOSFET
MOSFET tester:
NiCd Battery Discharger / Capacity Indicator:
Off Line Telephone Tester: Here is a circuit of an off-line Telephone tester which does not require any Telephone line for testing a Telephone instrument. The circuit is so simple that it can be easily assembled even by a novice having very little knowledge of electronics. FAIR WARNING -- THIS SITE HAS ANNOYING POP UP ADS.
Owens Bridge Inductance Measurement Device:
Paralleling RMS Converters Speeds Settling.: 05/26/94 EDN-Design Ideas
PC Based Digital Storage Oscilloscope (DSOA):
PC Based Digital Storage Oscilloscope Mk3:
PC hardware Monitor Reports the Weather: 01/18/01 EDN-Design Ideas / PDF contains multiple circuits - scroll to find the one of interest -
PCB VSWR Bridge:
pH Meter #1:
pH Meter #2:
pH Meter With Calibration:
Phantom Power Battery Test Circuit: LED will light when battery is over42 volts
Picoammeter Circuit With Four Ranges: This circuit uses a CA3420 BiMOS op amp to form a picoammeter with4 ranges. The exceptionally low input current (typically0.2pA) makes the CA3420 highly suited for use in a picoammeter circuit. Input transient protection is provided by the1 megohm resistor in series with the input. The10 megohm resistor connected to pin2 decouples the potentially high input capacitance often associated with lower current circuits and reduces the tendency for the circuit to oscillate under these conditions. The10k potentiometer is used for null offset.
Pink Noise Generator for Audio Testing:
Polarity Sensing Continuity tester:
Power Factor Meter:
Pre Distortion Techniques: Tape Linearizer and a Distortion Analyzer
Precision Audio Frequency Peak Detection Probe : for use with a digital voltmeter
Precision Audio MilliVoltmeter: Measures10mV to50Volt RMS in eight ranges Simply connect to your Avo-meter set @50µA range
Pulse Generator & Signal Tracer: Dual-purpose test-instrument Very simple Circuitry,1.5 Volt Battery-operated
Pulse Generator Verifies Test Setups: 05/26/94 EDN-Design Ideas / Verifying the rise-time limit of wideband test-equipment setups is a difficult task. In particular, you must often know the "end-to-end" rise time of an oscilloscope/probe combination to ensure measurement integrity. Fig1s circuit provides an 800-psec pulse having rise and fall times shorter than250 psec. The pulses amplitude is10V, and the circuits source impedance is50 Ohm.
Ramp Generator:
Remote Control using Telephone: Here is a tele-remote circuit which enables switching "on" and "off" of appliances through Telephone lines. The circuit described here can be used to switch up to nine appliances (corresponding to the digits1 through 9 of DTMF the Telephone key-pad). The Telephone can be used to switch on or switch off the appliances also while being used for normal conversation. FAIR WARNING -- THIS SITE HAS ANNOYING POP UP ADS.
Remote Field Strength Meter:
Remote humidity sensor needs no battery: 04/04/2002 EDN - Design Ideas / Using ac-line power sources and batteries for remote humidity sensors is undesirable because these sources can be troublesome if you mount them in inaccessible points, such as smokestacks, cold-storage chambers, or darkrooms, where maintenance is difficult and inconvenient. Figure 1 shows a simple way to remove the power source from the humidity-sensor circuit. .
Ring Oscillator Measures Cable Length: 05/12/94 EDN-Design Ideas
RJ45 Cable Tester:
RMS to DC Converter is Accurate & Stable: 09/14/95 EDN-Design Ideas
Scope Probe Measures High Frequencies: 01/18/96 EDN-Design Ideas
Self Heated Transistor Digitizes Airflow: 03/14/96 EDN-Design Ideas
Self Oscillating Amplifier for Distortion Testing: allows the home constructor to make quite accurate measurements, without having to spend a lot of money on a low distortion oscillator
Self Powered Fast Battery Tester: Tests1.5 to15 Volt cells2-LED display, no power supply required
Short Circuit Finder uses Few Parts: 11/05/98 EDN-Design Ideas
Signal Conditioning Precisely indicates Humidity: 02/02/98 EDN-Design Ideas
Signal Generator for Signal Tracer:
Simple 6 Digit 40MHz Frequency Counter Module:
Simple BER meter is easy to build: 03/02/00 EDN-Design Ideas / A bit-error-rate (BER) tester is a basic tool for digital-communications measurements. Although many commercial BER testers are available, you can easily design and build an inexpensive version. The scheme in Figure 1 has performance similar to that of a...
Simple Circuit Measures VI Phase Displacement : 08/19/02 Electronic Design - Ideas for Design / This circuit provides different ways to measure the current-voltage phase displacement of a line-powered ac load. The classic approach for sensing an ac load's current requires a transformer or sensing resistor. The transformer may be expensive,...
Simple circuit provides high side current sensing: 10/12/00 EDN-Design Ideas / PDF contains multiple circuits - scroll to find this circuit
Simple Circuit Provides Timebase Calibration: 04/24/97 EDN-Design Ideas
Simple Circuit Uses Optical Fiber To Send RelativeHumidity Data : 04/01/02 Electronic Design - Ideas for Design / The circuit shown in the figure measures relative humidity in air at the low temperatures found in applications like cold storage of food items and greenhouses. Instead of using electrical signal cables that...
Simple emulator speeds testing : 09/25/03 EDN-Design Ideas / Designing and testing embedded hardware can be frustrating if you have to rely on somebody else's perhaps-unready firmware to test your hardware. Often, hardware is ready for testing before debugging and system firm-ware are available from software developers. Microprocessor emulators are solutions but are often expensive, hard to use, and sometimes inappropriate for use by hardware developers,......
Simple ESD gun Tests IC: 09/12/96 EDN-Design Ideas
Simple Logic Probe uses Bicolor LED: 03/13/98 EDN-Design Ideas
Simple Technique Measures Small Capacitance: 09/01/97 EDN-Design Ideas
Simple tester checks LCDs: 10/03/2002 EDN - Design Ideas / Manufacturers of electronic equipment use LCDs for calculators, watches, mini-videogames, and pagers, for example. In comparison with LED-based displays, which consume power on the order of tens of milliwatts, an LCD consumes only a few microwatts. The LCD thus saves power by a factor of approximately 1000..
Simple, LowCost Capacitor Matcher Replaces Expensive Lab : 11/11/02 Electronic Design - Ideas for Design / Matching several capacitors, without needing a really precise value, can be accomplished with a "high-tech" laboratory capacitance meter. But this is cumbersome and overkill, and not everyone has one. This simple circuit matches, compares, and even...
Synthetic Isolators: great for checking the SWR of antennas, amplifiers, mixers, etc.
Telephone Test Circuit With Audio Mixer: get Telephone audio to mixer or send audio to Telephone
Temperature Compensated PH Meter:
TempSentry Temperature Sensor Technical Info & Schematics:
Test Batteries Without a Voltmeter: 11/09/00 EDN-Design Ideas / PDF contains multiple circuits - scroll to find the one of interest / This circuit an easy approach to testing batteries without exiting the voltmeter. The battery holders in sizes AAA, AA, C, and D make this tester so much faster than a voltmeter.
Three Channel Spectrum Analyzer: This Three 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.
Three Level Audio Power Indicator: Battery-operated Three LED display that connect it to loudspeaker output
Time and Frequency Circuits:
Time Domain Reflectometer (TDR):
Time tag impulses with zero crossing circuit: 01/24/2002 EDN - Design Ideas / A "constant-fraction discriminator" usually performs the time-tagging of impulsive events, which have a peaking time of the signal amplitude. The implementation of this technique requires a delay in the input signal of approximately the same amount as the signal's rise time. You can attain this delay by using a coaxial cable of an appropriate length. .
Tonal Voltmeter gives Audible indication of Voltage Level:
Trace voltage current curves on your PC: 10/11/2001 EDN - Design Ideas / Some years ago, one of the fundamental electronic instruments was the laboratory curve tracer. A CRT display would sweep out terminal behavior (current versus voltage) from which you could derive mathematical models. Classic presentations of diodes, transistors, and other devices enlightened designers about linear and nonlinear operation. .
Track multisite temperatures on your PC: 04/18/2002 EDN - Design Ideas / The low-cost circuit in Figure 1 allows you to track four remote temperatures with thermistor sensors through the parallel port on your PC. This four-zone thermometer instrument has a temperature range of -40 to +90 C and a resolution of better than 1 C. You can calibrate its accuracy to within 1 C over a 0 to 50 C span and within 3 C over a -40 to +90 ... .
Transistor & FVCs Make Linear Anemometer: 09/26/96 EDN-Design Ideas
Transistor tester fits into your pocket: 12/20/2001 EDN - Design Ideas / It can be helpful to rapidly and easily determine the polarity (npn or pnp) and function of a transistor. The pocket-transistor tester in Figure 1 is ideal for quickly testing without regard to such parameters as gain and frequency response. You connect the transistor, or device under test, between the collectors, T, of an astable multivibrator.
Transistor Trio Makes Vector Anemometer: 09/01/97 EDN-Design Ideas
Transmission line tests 1 kW device using only 100W: 02/20/03 EDN-Design Ideas / A 13.56-MHz, ISM (industrial, scientific, and medical)-band RF-measurement device had the test requirement of a 50-hour, 1-kW burn-in. The device under test needed to be simultaneously stressed at an RF potential and RF current equivalent to 1 kW, but the only spare RF source at hand was a 100W RF generator...
Transmitter accurately transfers voltage input: 05/15/03 EDN-Design Ideas / When you connect remote sensors to a central process controller, a simple, robust, and commonly used interface is the 4 to 20-mA loop. The advantages of this current loop include the simplicity of just two twisted wires that share both power and signal, the loop's high noise immunity in harsh environments, and the de facto loop standard within the process-control industry...
Tri Waveform Generator:
Triangle and Squarewave Generator:
True RMS Detector: National Semiconductor Application Notes,28-Jun-1996
TTL Pulse Reading Logic Probe:
Two Sensors Measure Three Line Currents: 09/01/95 EDN-Design Ideas
Two Tone Audio Oscillator (use for SSB Tests):
Ultra Simple Voltage Probe:
Understanding Peak Reading Meters: includes1-example circuit diagram
Versatile power supply load uses light bulbs: 02/07/2002 EDN - Design Ideas / Improvising loads for bench-testing and designing power supplies is often a frustrating and sometimes hazardous experience. When you push large power resistors to their limit, they tend to burn benches and melt solder connections. Many electronic loads are on the market but are usually expensive and of laboratory-type precision and often represent overkill for the average designer. .
Voltage Reference improves JFET: 10/26/00 EDN-Design Ideas / PDF contains multiple circuits - scroll to find this circuit The common JFET current-source in Figure 1a has average output impedance and depends heavily on the JFET's V P and I DSS variations. These manufacturing variations limit the initial accuracy of the current setpoint that the circuit can obtain with a...
VU & PPM Audio Metering: circuits using analog needle meters
VU Meter: 5 led VU meter, in PDF format, includes circuit board, text in Finnish
VU Stereo Meter: will indicate the volume level of the audio going to your speakers by lighting up LEDs, based on LM3915 IC