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Tester or Instrumentation Circuits, Page 3b
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Last Updated on: Wednesday, November 29, 2017 05:38 AM

Circuits Designed by Dave Johnson, P.E. :
  • CAPACITANCE TYPE LIQUID LEVEL MONITOR
    This circuit was originally designed to monitor the level of liquid natural gas in a tank but it can be used to also measure almost any liquid. Two custom insulated metal tubes form a capacitor plate. The capacitance between the two tubes increases as the level of the liquid rises. The circuit converts an increase of capacitance into a positive voltage change. The circuit could be changed to handle almost any scale factor needed.

  • Cheap Electrostatic Discharge Tester
    Anyone who has ever had a shocking experience on an especially dry day is acutely aware of the kinds of high voltage that can be generated from a simple walk across a carpeted floor. Those same finger to metal sparks can destroy or disrupt sensitive electronic circuits. Good design practices take great care to avoid such potential disasters by maintaining sufficient insulation between metal or plastic enclosure parts and the electronics within or by shielding any especially sensitive components....
  • Cheap Light Power Meter
    Some time ago I was experimenting with the use of some low leakage photovoltaic solar cells, to harvest some energy from the diffuse lighting inside a room.  The plan was to use a small array of solar cells (the type often used on solar powered calculators) to keep a super capacitor charged, drawing power from the light within an inside room..
    .
  • Clear Fluid Detector #2
    Using an ultra low power technique, this circuit detects when a clear fluid is inside a piece of clear plastic tubing. It can be used for fluid level control and monitoring.

  • Clear Fluid Detector
    This circuit detects when a clear fluid is inside a piece of clear plastic tubing. It can be used for fluid level control and monitoring.


Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:
Circuit checks consistency of binary addresses -  09/28/95 EDN-Design Ideas....The validation circuit in Fig 1  allows you to check the consistency of successively recurring 3-bit address codes. The circuit simultaneously applies the address code to the A port of IC2, a 7485 magnitude comparator, and to IC3, a 1-of-8 decoder. When IC2's B port reads the same address latched on the output of D flip-flop,.... [Design Idea by Arthur Edang, Don Bosco Technical College, Mandaluyong, Philippines]

Circuit Detects & Disconnects OverVoltages -  04/25/96 EDN-Design Ideas....The circuit in Fig.1 protects circuits and systems with power supplies that may exceed safe limits. One example is small consumer products that use external ac adapters; it's easy to mistakenly plug in the wrong adapter. Another example is a portable system that uses a rechargeable battery pack. If the battery pack is absent or fails to open during recharging, a high-compliance charger can deliver excessive voltages to the system.... [Design Idea by Kerry Lacanette, National Semiconductor Corp, Santa Clara, CA]
Circuit Detects DC Ringing -  08/17/00 EDN-Design Ideas  EDN is migrating links. This link is not verified.  Search the "title" + "EDN" for new link.
Circuit detects first event -  05/03/01 EDN-Design Ideas.... EDN is migrating links. This link is not verified.  Search the "title" + "EDN" for new link.
Circuit Detects Loss of 4-20 Ma Signal -  National Semiconductor Application Note....[App Note]
Circuit detects reset source -  04/27/00 EDN-Design Ideas EDN is migrating links. This link is not verified.  Search the "title" + "EDN" for new link.
Circuit distorts duty-cycle for CML inputs -  5-Aug-04 Issue of EDN  To test a gigabit-speed data-recovery chip, you need a clock with a controllable duty cycle. Because most pattern and clock generators have a fixed duty-cycle output of 50%, the design may require a small circuit to distort the duty cycle. The signal with controllable duty cycle drives a standard CML (current-mode-logic] input with on-chip termination resistors.... [Design Idea by Dieter Verhulst and Xin Yin, Ghent University, Belgium]
Circuit eases power-sequence testing -  9-Jul-09 Issue of EDN  A low-cost design controls power-up of two power sources.... [Design Idea by Goh Ban Hok, Infineon Technologies Asia Pacific Ltd, Singapore]
Circuit eases three-phase monitoring -  12/17/98 Issue of EDN   Measuring line-to-line voltages in a delta-connected three-phase system can present special problems. Because all three lines may be floating several hundred volts above ground, you can not use nonisolated, grounded oscilloscopes or other single-ended instruments. Special isolation amplifiers are available for oscilloscopes, but they can cost several thousand dollars. You still need to make three measurements even with proper instrumentation....Page includes several designs.  Scroll to find this one.... [Design Idea by Henno Normet, Tavares, FL]
Circuit lets you measure zener voltages and test LEDs 10-Jun-10 Issue of EDN  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 provides 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.... [Design Idea by Vladimir Oleynik, Moscow, Russia]
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