Machine Vibration Activates Hour Meter:  01/16/97 EDN-Design Ideas  by David Johnson Battery-powered digital hour meters commonly monitor how long a machine is in operation by detecting when the machine is supplied with power. However, it is often difficult or dangerous to connect a battery-powered hour meter to a line-powered machine. When the machine being monitored produces de-tectable vibrations, you can use the circuit in Figure 1, which doesn't require any power-line connections. The circuit uses just one IC and allows you to turn a battery-powered hour meter on and off according to a machine's vibration.  (added 09/05)

Magnetometer:  (schematic added 8/03)

Make a Low Cost Benchtop Power Meter:  09/11/98 EDN-Design Ideas / (added 6/06)  

Make Your Own Shunts:  Using a modern multimeter to measure current can sometimes be difficult.  Many of these meters will only measure up to one amp.  However, may 112-volt DC powered projects draw a lot more than that. If you have ever thought of purchasing a commercial shunt to solve the problem, your know just how expensive they can be.  Commercial shunts, while very precise, frequently cost more than the projects they are measuring!  However, there is a better and cheaper alternative that will work perfectly well in most situations... (added 2/06)

Making Differential Probes:  For sensing audio signal voltages across devices that are not ground referenced (added 6/03)

MAR/RAM Test Fixture Instructions  AN-60-018:  Application Note MiniCircuits.com  (app note added 6/06)

MAV Test Fixture Instructions  AN-60-025:  Application Note MiniCircuits.com  (app note added 6/06)

Measure humidity and temperature on one TTL line:  08/30/01 EDN Design Ideas  /  (added 1/05)  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 open circuited cables using a multimeter:  09/26/02 EDN Design Ideas  /  (added 1/05)  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 the capacitance per foot of wire, then you can calculate how far it is to the open circuit....

Measure temperature in remote locations:  10/12/00 EDN-Design Ideas / (added 6/06)

Measurement methods:  Application Note MiniCircuits.com  (app note added 6/06)

Measuring AC Frequency using Pulse Width Measurement Mode:  Toshiba 870X Series Application Note  (app note added 2/06)

Measuring Jitter in Digital Systems (AN 1448-1):  Agilent Application Note   (added 6/06)

Measuring RF Voltages with a VOM:  (schematic added 8/03)

Measuring self resonant frequency:  Coilcraft RF Magnetics Application Notes -(added 6/06)

Measuring sensitivity of transponder coils:  Coilcraft RF Magnetics Application Notes -(added 6/06)

Method simplifies testing high Q devices:  02/21/02 EDN Design Ideas  /  (added 1/05)  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. ...

Method Tests Cables:  10/17/02 EDN Design Ideas  /  (added 1/05)  Engineers have long known how to test a cable for continuity by simply connecting all conductors in series and checking with an ohmmeter. This method is sometimes impractical, however, because it cannot check for short circuits. The method shown in Figure 1 solves the short-circuit problem. Connecting LED indicators at each shorting loop provides a visual indication....

Microphone Circuit Test Oscillator:  440 Hz Tone generator for testing XLR microph1-lines (added 5/02)

Microphone Polarity Tester:  (electronic schematic / circuit added 4/02)

MIDI interface/cable tester:  (circuit / schematic added 6/05)

MIDITester:  (circuit / schematic design added 6/06)

MilliGauss Meter:  (electronic design added 9/02)

Mini DDS (direct Digital Synthesizer):  (schematic added 8/03)

Mini DDS Synth:  (project / circuit added 10/06)

Missing Codes Tester Checks 16 Bit ADC in 7 Sec:  06/10/99 EDN-Design Ideas / (added 6/06) As the resolution of ADCs increases from 12 to 16 bits and higher, the difficulty in testing the "nomissing-codes "specification grows proportionately. To fully guarantee no missing codes for a 16-bit ADC requires testing all 2 16-1 possible output...

Mixed Signal Testing using the IEEE 1149.4 STA400:  National Semiconductor Application Note   (app note added 2/06)

Modified Scope Probe Tests Surface Mount Assemblies:  09/25/97 EDN-Design Ideas / (added 3/03)  

Monitoring Additional Supplies with the ADM1062-ADM1069 Super Sequencers™:  AN-781 Analog Devices Application Note   (app note added 6/06)

Monitoring High Voltages with the ADM1062-ADM1069 Super Sequencers™:  AN-782 Analog Devices Application Note   (app note added 6/06)

Monitoring Negative Voltages with the ADM1062-ADM1069 Super Sequencers™:  AN-780 Analog Devices Application Note   (app note added 6/06)

Morse Monitor:  (circuit / schematic design added 6/06)

MOSFET  Tester:  This testing procedure is for use with a digital multimeter in the diode test-range with a minimum of 3.3 volt over d.u.t. (diode-under-test). 
If your multi-meter is less than that it will not do the test.  Check your meter manual for the specs. (added 2/06)

Moving coil meter measures Low level Currents:  03/03/05 EDN Design Ideas  / (added 5/05)  Although an analog moving-coil meter may lack the resolution and accuracy that a digital readout provides, a meter remains the display of choice for certain applications. A digital readout simply cannot provide information about a measurement's rate of change, and tracking a reading's trend is easier on an analog meter.

MPU temperature meter #2:  Multi point diode temperature meter to replace thermister temperture meter. This is for diode temperture sensors icludes on-die thermal diode of micro-processor.  (added 6/06)

MPU temperature meter:  Multi point temperature meter which displays tempertures to an LED display with time divided. This is good for monitoring temperature of PC components.  (added 6/06)

Multi Wire Cable Tester:  (electronic schematic / circuit added 4/02)

Nitrogen Spark Generator:  (circuit / schematic added 6/05)

Noncontact Devicetests power supplies:  03/01/01 EDN-Design Ideas / (added 2/06)

NTSC Test Signal Generator:  An accurate test signal generator for television calibration and measurements.  (added 6/06)

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.   (added 5/02)

Opacity Meter:  File contains several circuits, scroll to find this one (added 2/05)

OpAmp Design and Test Board:  (electronic schematic / circuit added 4/02)

Optimizing Bluetooth DeviceBattery Drain Measurements in Manufacturing (5988-6064EN):  Agilent Application Note 1396 (added 4/08)

Owens Bridge Inductance Measurement Device:  The circuit is a very simple RCRCRC filtered supply and a current source. The filtered supply provides 174 bolts at no load, and drops to 106 volts at 400mA. Ripple must be relatively low. In this supply, ripple is about 2 mV at 400mA load, so it is sufficiently filtered. Available voltage ranges from 154 volts at 100mA to 136 volts at 200mA to 106 volts at 400mA. The current source consists of a single IRF730 with a degeneration resistor in series with the source. About 14 volts maximum is placed on the gate, and with 4 volts gate-to-source voltage, a 100 ohm resistor in the source will develop 100mA. That resistor is range switched . 100 ohms is used for the Lx10 range, allowing 100mA maximum on that range, but an additional 100 ohm resistor is paralleled for the Lx1 range to allow 200mA, and an additional 50 ohms is paralleled on the Lx0.1 range for higher current. ...  (added 8/03)