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Sensors / Detectors: Schematics
Amp Meters and Current Monitors

4  to 20m loop needs no external power source - EDN-Design Ideas: The simple circuit in Figure 1 uses a low-current-drain MAX407)

AC Current Indicator Light - This circuit could be wired into a 120vac power line, which feeds power to any load, ranging from 40 watts to 250 watts.  It will turn on a LED light whenever current is being drawn by a load.  It is especially useful for remote lights, where you may not be able to see if the lamps are receiving power.

AC Line Current Detector - This circuit will detect AC line currents of about 250 mA or more without making any electrical connections to the line. Current is detected by passing one of the AC lines through an inductive pickup (L1) made with a 1 inch diameter U-bolt wound with 800 turns of #30, #35 magnet wire. The pickup could be made from other iron type rings

Active feedback IC Serves as current sensing instrumentation Amplifier - EDN-Design Ideas:   High-speed current sensing presents a designer with some significant challenges. Most techniques for sensing current involve measuring  differential voltage  current produces as it flows through.

AN-244: A User's Guide to I.C. Instrumentation Amplifiers - AN-244 Analog Devices Application Notes

AN-245: Instrumentation Amplifiers Solve Unusual Design Problems - AN-245 Analog Devices Application Notes  (app note added 2/06) Traditionally Considered Only for Transducer-Conditioning Applications, Instrumentation Amplifiers Bring Unique Performance Benefits to a Range of Or Applications as Well.

AN-282: Fundamentals of Sampled Data Systems - AN-282 Analog Devices Application Notes

AN-345: Grounding for Low-and-High-Frequency Circuits - AN-345 Analog Devices Application Notes  (app note added 2/06) Know Your Ground and Signal Paths for Effective Designs. Current Flow Seeks Path of Least Impedance-Not Just Resistance....

Zetex - High Side Current Monitor: App Note.

AN39 Current Measurement Applications Handbook - Zetec Semiconductors  Applications Notes This applications handbook explores how  requirements affect  design for AC and DC current measurement and  implications on cost and performance for different approaches.

AN-539: Errors & Error Budget Analysis in Instrumentation Amplifier Applications - AN-539 Analog Devices Application Notes Describes a systematic approach to calculating  overall error in an instrumentation amplifier application.

AN-589: Ways to Optimize the Performance of a Difference Amplifier - AN-589 Analog Devices Application Notes.  This Application Note presents several ways to build and optimize  performance of a discrete difference amplifier. It also recommends amplifiers that will make  overall solution cost/performance competitive with monolithic instrument amplifiers.

AN-597: Current Feedback Amplifiers - National Semiconductor Application Note

AN-671: Reducing RFI Rectification Errors in In-Amp Circuits - AN-671 Analog Devices Application Notes

AN-683: Strain Gage Measurement using an AC Excitation - AN-683 Analog Devices Application Notes

AN-772: A Design & Manufacturing Guide for the Lead Frame Chip Scale Package - AN-772 Analog Devices Application Notes

AN-840: Development of an Extensive SPICE Macromodel for 'Current-Feedback' Amplifiers - National Semiconductor Application Note

Analog input circuit Serves any microController - 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  cost of a single-chip- ADC approach in  same volume. Moreover, this design takes only one pin from  microcontroller to operate.

Bias Voltage & Current Sense Circuits for Avalanche Photodiodes - AN92 Linear Technology Avalanche photodiodes, used in laser based fiberoptic systems, require high voltage bias and accurate, wide range current monitoring. Bias voltage varies from 15V-90V and current ranges from 100nA to 1mA, a 10,000:1 dynamic range. This publication presents various 5 volt powered circuits which meet se requirements. Appended sections detail specific circuit techniques and cover measurement practice.
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