test/measurements

Current sense circuit collection

Here is a PDF document from Linear Technology, featuring current sense circuits for different applications, including High side, low side, level shifting, high and low voltage, fault sensing, etc: [ via ] Sensing and/or controlling current flow is a fundamental requirement in many electronics systems, and the techniques to do so are as diverse as the applications them-selves. This Application Note compiles solutions to current sensing problems and organizes the solutions by general application type

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Use a transistor and an ammeter to measure inductance

Raju Baddi writes: Bipolar junction transistors transfer a current from a lower-resistance emitter to a higher-resistance collector. You can use this property to measure inductance by connecting a series inductance/resistance circuit in the emitter and biasing on the transistor long enough for the current to reach a maximum value that is at least five LR time constants

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TrH Meter: A DIY indoor thermometer plus hygrometer with adaptive brightness

This project is about building a microcontroller-based digital room thermometer plus hygrometer that displays temperature and relative humidity on 4 large (1 inch) seven segment LED displays which adjust their brightness level according to the surrounding illumination. It consists of a closed loop system that continuously assesses ambient light condition using an inexpensive light-dependent resistor (LDR) and uses that information to adjust the brightness of the display.

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Complete, low-cost, software programmable ohmmeter measures micro-ohms

Moshe Gerstenhaber and Mark Champion write: Numerous applications require the measurement of very low resistances, including but not limited to fuse integrity analysis, relay characterization, and superconductor evaluation.  There is a wide range of commercially available equipment designed for this task, but these units are prohibitively expensive and cannot be practically integrated into many applications outside the laboratory.  A common low-cost and compact method of measuring resistance is to inject a known dc current into the unknown resistor, measure the resulting voltage and calculate the resistance using Ohm’s law.  Unfortunately, for very low resistances, the current required to generate a voltage sufficiently distinguishable from the surrounding noise becomes impractically large. Complete, low-cost, software programmable ohmmeter measures micro-ohms – [ Link ] Low Ohm Meter – Measures 0.001 up to 1.999 Ohm Accurate Milliohm Measurement AC Ohmmeter – ESR Meter Ohm’s Calculator Test the safety of your devices with the VA588 multimeter

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