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Tester or Measurement (Instrument) Circuits

Test Equipment:  #'s - A        B - D        E - G
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Last Updated: October 24, 2017 02:55 PM
Circuits Designed by Dave Johnson, P.E. :

Circuit Indicates Battery Charge Current -  This circuit was inspired by a company needing a DC current indicator light which was small enough to be molded into a medium size 28v rechargeable battery assembly.  They specified that they wanted the circuit to turn on the LED indicator light with 500ma or more of battery charge current . . . Hobby Circuit designed by David A. Johnson P.E.-January, 2011

Circuit Monitors 120 Power Line -  This hobby electronic circuit produces a short beep once each minute.  it is powered directly off the 120vac power line to remind you that a device connected to the circuit is turned on.  it is simple enough to be packaged inside a small plastic box . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

Circuit Monitors 12v Lamp Current  -  This circuit monitors DC current and turns on a LED indictor light whenever DC current flows into a 12v lamp . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Circuit Monitors Power Loss -  For some medical equipment it is important for an operator to know when power is lost to the machine.  The beeper is powered from a 9v battery and requires the machine to have a power switch with a third set of contacts . . . Hobby Circuit designed by David Johnson P.E.-March, 1999

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Circuit Improves On Earlier Idea -  EDN Design Ideas:  05/24/2012   A self-biasing thermistor circuit had an overall dominant thermal/electrical time constant as small as 25 msec but had a significantly rounded response following a square (thermal) input pulse of 100 msec; the source was a pulsed blue LED.  A single-op-amp-based “anticipator-like” circuit generated a more faithful picture of the actual input excitation, and improved on the circuit described in a previous Design ideas (Reference 1).  The lowpass filter in Figure 1, with an RC time constant of approximately 25 msec, models the circuit. __ Circuit Design by Nicholas Lockerbie, Scottish Universities Physics Alliance, Glasgow, Scotland

Circuit improves on first-event Detection -  08/16/01 EDN Design Ideas:  The circuits in Figure 1 and Figure 2 exhibit certain advantages over the circuit shown in the Design ideas in EDN, "Circuit detects first event, " May 3, 2001, pg 89.  The n-player first-event-detection circuit offers several improvements  it has fewer passive components.  it needs only n diodes instead of (n2+n]/2 for three orplayers __ Circuit Design by Lawrence Arendt, Oak Bluff, MN, Canada

Circuit improves on temperature measurement -  05/02/02 EDN Design Ideas:  When current pulses with a stable iHiGH/iLOW ratio modulate a semiconductor junction, the ensuing voltage difference (for example, ΔVBE for a bipolar transistor] is a linear function of the absolute (Kelvin] temperature, T.  You can use this truism to make accurate temperature measurements.  Technical literature has thoroughly covered the relationship (references 1 to 4] and has numerou __ Circuit Design by Alexander Bell, Infosoft International Inc, Rego Park, NY

Circuit Indicates Battery Charge Current -  This circuit was inspired by a company needing a DC current indicator light which was small enough to be molded into a medium size 28v rechargeable battery assembly.  They specified that they wanted the circuit to turn on the LED indicator light with 500ma or more of battery charge current . . . Hobby Circuit designed by David A. Johnson P.E.-January, 2011

Circuit Indicates Health Of Lithium-Ion Batteries -  05/14/09  EDN Design Ideas:  A simple inexpensive circuit quickly indicates a battery pack's health __ Circuit Design by Fritz Weld, Friedberg, Germany

Circuit Lets You Characterize JFETs -  04/06/12  EDN Design Ideas:  Measure the pinch-off voltage VP and zero-bias drain current iDSS to select matched pairs of JFETs.   __ Circuit Design by John Fattaruso, Dallas, TX

Circuit lets you isolate & measure current -  09/23/10 EDN Design Ideas:  isolation lets you measure current with an oscilloscope or other grounded probe.    __ Circuit Design by Anton Mayer, Murr, Germany

Circuit Lets You Measure Zener Voltages & Test LEDs -  10-Jun-10 EDN Design Ideas:  To measure a zener diode's breakdown voltage, you need a dc voltage source whose voltage exceeds that of the zener voltage.  in Figure 1, resistor RSER provide as voltage drop between ViN and VZEN.  in any case, ViN  should exceed VZEN.  Resistor RSER must provide current, iZEN, that can keep the zener diode in reverse breakdown.  That is, the current must be more than iZEN-iZENMiN  and less than iZEN-iZENMAX.  You also need to consider the current that flows through the load.  Otherwise, VZEN  will be unregulated __ Circuit Design by Vladimir Oleynik, Moscow, Russia

Circuit Lets You Test Capacitors -  EDN-Design ideas -- 02/17/11    Check capacitors for leakage.  Electrolytic capacitors tend to leak with time.  The circuit in Figure 1 lets you test capacitors and decide whether they’re worth using.  You can set the constraint on the leakiness through the values of CREF/RREF.  The values in the figure are typical for general testing of all capacitors, from 1-nF ceramic versions to 1000-μF electrolytic types.  The value of CREF in the circuit is near the value of the test capacitor, CX.  You can also choose RREF, by a rotary-switching arrangement, to be greater than or less than 22 MΩ.   __ Circuit Design by Raju R Baddi, Tata Institute of Fundamental Research, Maharashtra, India

Circuit Lets You Test Sample-And-Hold Amplifiers -  4-Mar-10 EDN Design Ideas:  Measure voltage drop with a digital voltmeter __ Circuit Design by Marián Štofka, Slovak University of Technology, Bratislava, Slovakia

Circuit Linearizes, Converts Thermistor Data -  12/07/95 EDN Design Ideas:  Although the response of thermistors is inherently nonlinear, you can make the devices' resistance over a selected range of temperatures linear.  You can convert the thermistor value to a voltage for display on either a DMM or a panel meter.  The circuit in Figure 1 performs linearization and provide as gain and offset for a YSI 44031 thermistor, whose nominal resistance is 10 k[ohm] at 25şC.    __ Circuit Design by Matthew Beckner, Ball Corp Boulder, CO

Circuit Measures Battery Capacity -  EDN-Design ideas -- 06/09/11    Know how much cell or battery capacity you use to power a device.  Batteries and energy cells lose their capacity as they age.  if a cell or battery’s capacity is too low, your equipment may also soon stop working.  You can use the circuit in Figure 1 to measure a battery’s discharge time.  The circuit uses an electromechanical clock and a DVM (digital voltmeter).  The cell should be fully charged before testing.  The circuit discharges the cell at a fixed current and measures the time it takes to discharge the cell from 100 to 0%.
 __ Circuit Design by Vladimir Oleynik, Moscow, Russia

Circuit Measures Capacitance or Inductance -  10/21/10 EDN Design Ideas:  Use instruments you already have and a few equations when you don’t have a capacitance meter.   __ Circuit Design by Jim McLucas, Broomfield, CO

Circuit Measures Diesel's Rotations Per Minute -  03/04/99 EDN Design Ideas:  (Scroll to find this one) The circuit in Figure 1 uses a Dallas Semiconductor DS1820 one-wire digital thermometer in a multipoint temperature-measurement system.  The DS1820 sensor allows distributed temperature measurement and uses only one wire for both data communication and the power supply.  You can easily connect the one-wire interface to a µC (in this example, a PIC 16C63).  The application accommodates as many as 16 DS1820 sensors in a 100m-long network, dubbed MicroLAN by Dallas.  Unfortunately, with such long wires near high-current power cables, inductively coupled high-voltage peaks can cause µC latch-up, because the transient-voltage suppressor, D1, cannot limit the line voltage below 9.8V.  The interface circuit in Figure 1 prevents such faults.   __ Circuit Design by David Magliocco, CDPI, Scientrier, France

Circuit Measures Optocoupler's Response Time -  09/08/11  EDN Design Ideas:  Measure the response speed of optocouplers in order to select matching devices.  You can use the circuit in this Design idea to measure the attack and release times of photoresistor-type optocouplers (Figure 1).  Such devices often find use in audio compressors or volume-control circuits.  The design uses an oscillating Schmitt trigger with the optocoupler DUT (device under test) in the feedback loop.  The photoresistor and resistor R1 form a voltage divider that controls the input of the Schmitt trigger.   __ Circuit Design by Peter Demchenko, Vilnius, Lithuania

Circuit Measures Small Current in DC Servo Motor -  12/06/01 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 0.1Ω  __ Circuit Design by Shyam Tiwari

Circuit Measures Software-Execution Timer -  03/17/94 EDN Design Ideas:  Especially heLPFul for developing real-time application programs, the circuit in Fig 1 plugs into a PC printer port and measures the execution time of a piece of software.  The CD4536 is a 16/24-bit binary counter with a built-in oscillator.  This counter has an 8-bit prescaler, which the chip bypasses if the 8_BY pin is high.  When this is the case, the CD4536 is a 16-bit counter, and its A through D inputs select which bit is connected to output DO.  if the 8_BY pin is low, the CD4536 is a 24-bit counter and the inputs select __ Circuit Design by Yongping Xia, EBT Inc, Torrance, CA

Circuit measures true-rms & average value -  09/26/02 EDN Design Ideas:  The circuit in Figure 1 measures both the true-rms value and the rectified average value of an ac signal.  This design uses two low-cost ICs  in SOIC  packages and consumes only 180 µA of quiescent current.  Operating from a single 5V supply, the circuit has an input dynamic range of less than 30 mV to greater than 3V rms __ Circuit Design by Charles Kitchin and Lew Counts, Analog Devices, Wilmington, MA

Circuit Monitor 2 -  PIC  Project  This is a circuit monitoring device.  it runs for over 10 days and can log up to 32k events both digital and analog.  Samples are logged either on a timing basis (.01 to 2.5 seconds) , or on a triggered basis.  Four inputs are provided, up to three of which can be analog __ Designed by Luhan Monat - Mesa Arizona

Circuit Monitors 120 Power Line -  This hobby electronic circuit produces a short beep once each minute.  it is powered directly off the 120vac power line to remind you that a device connected to the circuit is turned on.  it is simple enough to be packaged inside a small plastic box . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

Circuit Monitors 12v Lamp Current  -  This circuit monitors DC current and turns on a LED indictor light whenever DC current flows into a 12v lamp . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Circuit Monitors AC-Power Loss -  11/24/99 EDN Design Ideas:  The circuit in Figure 1 provide as a simple, nonvolatile means of monitoring critical ac-power failures.  Monitoring the power is important in such systems as heating and refrigeration, in which damage can occur if the ac power goes down for an extended period.  The circuit in Figure 1 requires little power from the ac-power system.    __ Circuit Design by Dennis Eichenberg, Parma Heights, OH

Circuit Monitors battery voltage -  11/21/96 EDN Design Ideas:  The circuit in Figure 1 monitors four NIC d rechargeable batteries and causes the LED to flash if the voltage of the batteries goes lower than 4V.  The circuit consumes only 8 mA of current under normal operating conditions.   IC 1 is an eight-pin IC that includes an op amp, a comparator, and a 1.2V zener diode.  The zener diode connects to the negative input of the comparator in the IC as a reference.  R6 and R7 divide the battery voltage __ Circuit Design by Yongping Xia, Philips Lighting Electronics Co, Torrance, CA

Circuit Monitors Multiple Contact Closures -  02/15/96 EDN Design Ideas:  The simple circuit in Figure 1 monitors multiple (15) pairs of relay contacts and provide as visual and electronic indications of contact closures.  A series-connected LED, current-limited by a 2.2-kOhm resistor, provide as a visual indication of each contact closure and remains lit while the contact is closed.  The circuit comprising a current mirror (Q1 and Q2) and comparator IC 1 provide as an electronic indication (a pulse at IC 1's output) of each contact closure.    __ Circuit Design by Richard McGillivray, Grey Bruce Regional Health Centre Owen Sound, Ontario, Canada

Circuit Monitors Power Loss -  For some medical equipment it is important for an operator to know when power is lost to the machine.  The beeper is powered from a 9v battery and requires the machine to have a power switch with a third set of contacts . . . Hobby Circuit designed by David Johnson P.E.-March, 1999

Circuit Monitors quad supply for PCI systems -  08/19/99 EDN Design Ideas:  Many modern systems operate with multiple power supplies that must meet tight tolerances to accommodate high-end µPs and peripherals.  For instance,  __ Circuit Design by Roger Zemke

Circuit Prevents Deep Discharge Of Batteries -  09/26/96 EDN Design Ideas:  To avoid the deep discharge that can destroy or shorten the life of a rechargeable battery, you must disconnect its load before the discharge is complete __ Circuit Design by Ron Clark and Larry Suppan, Maxim Integrated Products

Circuit prevents processor latch-up -  03/04/99 EDN Design Ideas:  Simple circuit prevents processor latch-up.  Dual one-shot makes rising- and falling-edge detector.  Simple circuit measures diesel's rotations per minute.  Fast, compact routine interfaces EEPROM to µC.  Photodetector sorts objects.  Single-button lock provide as high security.   __ Circuit Design by Michal Kobylecki and Wojda Wlodzimierz, MK Design, Warsaw, Poland

Circuit Produces a Less than 25 Nsec Pulse -  05/11/00 EDN Design Ideas:  in many testing situations, a circuit that can produce a short pulse is useful.  You can use a short pulse to test trigger or interrupt-pulse-width requirements and to mimic glitches or noise on inputs, for example.  in some cases, short pulses with long delays between them are desirable.  For these cases, a function generator is inadequate because you can reduce the duty cycle low enough to produce low-nanosecond pulse widths only at relatively high frequencies.  Although purely analog circuits can generate short pulses, input and output loading and buffering propagation delays create problems with interfacing them to TTL-compatible circuitry.   __ Circuit Design by Andy Brandenberger, National Instruments, Austin, TX

Circuit protects battery from overdischarge -  04/12/01 EDN Design Ideas:  All electronic circuits powered by a battery discharge the battery.  in some applications, it is undesirable to overdischarge the battery, because it could irreversibly reduce the battery’s capacity and the number of discharge/charge cycles.  The circuit in Figure 1 protectsPDF contains multiple circuits, scroll to find this circuit __ Circuit Design by Martin Wuzik, Implex AG Hearing Technology, Ismaning, Germany

Circuit Provides 1.5V, 7A Bus Termination -  EDN Design Ideas:  09/14/95    Some of the newest high-performance processors require a 1.5V bus terminator that can source currents as high as 7A.  This terminator requires a very fast transient response, because the device must react to high peak-current changes that have extremely fast rise times.  The 1.5V terminator circuit in Fig 1 meets these demanding requirements. __ Circuit Design by Chester Simpson and Mineo Yamatake, National Semiconductor, Santa Clara,CA

Circuit Provides Accurate RTD Measurements -  12/31/69 EDN Design Ideas:  The circuit in Figure 1 is an efficient measuring circuit for PT100 RTD elements.  IC 1 provide as an accurate 2.5V output and, together with P1 and R1 , also provide as a stable 1-mA current to the RTD element.  The output of IC 2 is –0.1V.  P2 provide as a zero adjustment (at 0°C) for IC 3 , an amplifier with a gain of 25.  P3 provide as a gain adjustment.  if, for example, you replace the RTD element by a fixed resistance of 124.78W (the RTD's resistance in Table 1 at 64°C) , you would trim P3 to obtain 0.64V output.   __ Circuit Design by Tito Smailagich, ENIC, Belgrade, Yugoslavia

Circuit provides Cold-Junction Compensation -  11/28/02  EDN Design Ideas:  The accuracy of any circuit or system that uses a thermocouple to determine the temperature of a process is limited by the accuracy of the method used to perform cold-junction compensation.  in a thermocouple measurement, two wires  __ Circuit Design by Mark Maddox, Analog Devices, Wilmington, MA, and John Wynne, Analog Devices, Limerick, Ireland

Circuit Provides High-Side Current-sensing -  10/12/00 EDN Design Ideas:  in power supplies or battery chargers, you often need information about the current flowing in the high-side rail.  Figure 1 shows a common circuit for obtaining this information.  The circuit provide as a groundreferenced voltage pr __ Circuit Design by M Ossmann and B Kazay Aachen University of Applied Sciences, Germany

Circuit provides ISFET-sensor bias -  10-Jun-04 EDN Design Ideas:  iSFETs (ion-sensitive field-effect transistors] are useful for measuring the acidity of fluids.  Accurate measurements require that the iSFET's bias conditions (iD and VDS] be held constant while the gate is exposed to the fluid under __ Circuit Design by Brian Harrington, Analog Devices, Wilmington, MA

Circuit Provides Simpler Power-Supply-Sequence Testing -  3-Dec-09 EDN Design Ideas:  New circuit improves on an earlier power-sequence-testing idea __ Circuit Design by Dan Karmann, DLK Engineering, Thornton, CO

Circuit Provides Visual Verification Of IR Pulses -  09/08/11  EDN Design Ideas:  Use a transimpedance amplifier to drive an LED.  You can test an IR (infrared) link with a circuit that converts an iR-generated photocurrent to an amplified current that drives a standard LED (Figure 1).  This approach provide as a visual feedback to indicate that the transmitter is working.  The circuit can be enclosed in a small plastic or metal box and requires just a 9V transistor battery for operation.  Diode D1 is a basic Everlight PD333-3C/H0/L2 or equivalent IR photodiode in a T1ľ package.   __ Circuit Design by Michael J Gambuzza, General Electric Measurement and Control Solutions, Billerica, MA

Circuit resolves 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 __ Circuit Design by Derek Redmayne

Circuit safely applies power to ICs -  11/22/01 EDN Design Ideas:  Supervisory circuits normally monitor a microprocessor's supply voltage, asserting reset to the IC during power-up, power-down, and brownout.  in this way, the circuit ensures that the supply voltage is stable before the microprocessor boots, thus preventing code-execution errors.  Many analog and digital ICs  also need a well-behaved start-up of their supply to avoid latch-up and logic-stat __ Circuit Design by Clayton Grantham, National Semiconductor, Tucson, AZ

Circuit Safely Deep Discharges NiCd Battery -  NIC d batteries possess an undesirable memory effect caused by partial discharges.  The remedy is to do a complete discharge before charging again.  Figure 1 shows a simple circuit which performs this feat.  Although relatively straightforward in concept, the circuit has three redeeming features: 1) it is powered by the battery being discharged.2) After the battery is fully discharged current drain is only about 4 uA, usually well below the self-discharge of a battery alone.3) Near end-of-charge the LED flashes.9publised 04/29/99 EDN-Design idea)  __ Designed by Jim Hagerman, Science & Technology International, Honolulu, HI

Circuit safely Deep-discharges NiCd battery  -  04/29/99  EDN-Design ideas –  NOTE:  Scroll to find this circuit.   Nickel-cadmium (NIC d) batteries can possess an undesirable memory effect due to partial discharges. The remedy is a complete discharge before charging again. Figure 1a shows a simple circuit that performs this feat.  __ Circuit Design by Jim Hagerman, Science & Technology International, Honolulu, HI

Circuit samples Derivative of a waveform -  09/14/00 EDN Design Ideas:  Basic derivative (differentiating) circuits use a lowpass filter or an active operational-amplifier implementation.  These circuits need a large-value capacitor when differentiating a slowly varying signal.  Moreover, the circuits  __ Circuit Design by Joaquin Garcia

Circuit senses high-side current -  03/01/01 EDN Design Ideas:  The accurate, high-side, current-sense circuit does not use a dedicated, isolated supply voltage, as some other schemes do.    __ Circuit Design by Bobell

Circuit Serves as Milliohm Meter -  04/15/04 EDN Design Ideas:  When I was recently debugging a design, I discovered that a short circuit existed from a ground plane to a power plane.  I did not have access to a milliohm meter or an equivalent tester for locating this type of short circuit.  So, I logged onto the internet to find an easily constructible milliohm meter __ Circuit Design by AM Hunt, Lancaster Hunt Systems Ltd, Shepperton, UK

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Test Equipment:  #'s - A        B - D        E - G
H - L        M - O        P - S        T - Z

 


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