Fluke app notes solve mysteries of digital multimeter

Fluke Corporation, the global leader in electronic test and measurement technology, has published a valuable series of application notes to help electricians and electronics professionals do advanced electrical testing with their Fluke digital multimeters (DMMs).

Advanced DMMs, such as the Fluke 289 Industrial Trending Digital Multimeter and Fluke 287 Electronics Multimeter, incorporate a multitude of sophisticated test and measurement capabilities. But some users may be unsure of how those capabilities are used, or why the tools are designed as they are. Fluke Application Notes, available through the Fluke website, are written and illustrated to take the mystery out, so Fluke users can solve problems and get the most from their Fluke test tools.

One new feature is the dual impedance capability built into the Fluke 289 DMM. Most DMMs sold today for testing industrial, electrical, and electronic systems have high impedance input circuits greater than 1 megohm. In simple terms, this means that when the DMM is placed across a circuit for a measurement, it will have little impact on circuit performance. This is the desired effect for most voltage measurement applications, and is especially important for sensitive electronics or control circuits.

Older troubleshooting tools generally have low impedance input circuitry around 10 kilohms or less. While these tools aren’t fooled by ghost voltages, they should only be used for testing circuits where the low impedance will not negatively impact or alter circuit performance.

With dual impedance meters, technicians can do it all: They can safely troubleshoot sensitive electronic or control circuits, as well as circuits that may contain ghost voltages, and can more reliably determine whether voltage is present on a circuit.

The Fluke application note explaining the use of dual impedance meters, “Dual impedance digital multimeters – What’s the point?” is available with other Fluke case studies and notes on the Fluke application notes web page for DMMs. It is also available through the Fluke applications notes page for all products at http://us.fluke.com/usen/support/appnotes/.