Profiling power: real-time current monitor

March 18, 2013

Jack Ganssle-March 18, 2013

As power becomes increasingly important, more tools are coming to market for measuring power use.

Consumers want their electronic gizmos to run from batteries for weeks, months, and sometimes years between recharges or primary cell replacements. Some devices are even harvesting their power from the environment. Achieving these feats means processors must be positively anorexic in their electron intake. And that suggests we need equipment to profile a product's power usage.

Recently I reviewed the ĀµCurrent, a small device designed to help monitor current consumption down to the nA range. It's aimed mostly at those who need accurate measurements of static power. It won't help profile a system that's dynamically going from nA to mA and back, since there's a range switch that has to be manipulated manually.

The Real-Time Current Monitor.
Click on image to enlarge.
A brand new unit has appeared: the Real-Time Current Monitor (I'll call it the RTCM, uncomfortably close to the acronym used to suggest one should consult a manual rather than ask questions). This device is rather innovative and a bit different from any other current monitor.

Real-Time Current Monitor
The unit puts a 1-ohm resistor in series with the device being tested and the power supply, and circuits monitor the drop. The output goes to an oscilloscope and is the log (base 10) of the current being consumed.

Strange, huh?

The best way to grok this is to use the unit.

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