• Skip to primary navigation
  • Skip to main content
  • Skip to primary sidebar
  • Skip to footer

Power Electronic Tips

Power Electronic News, Editorial, Video and Resources

  • Products
    • Power Supplies
    • AC-DC
    • DC-DC
    • MOSFETS
    • Power Management
    • Battery Management
    • RF Power
    • Resistors
    • Capacitors
    • Magnetics
    • Transformers
  • Applications
    • LED Lighting
    • Rack Mount
    • Wireless
  • EE Forums
    • EDABoard.com
    • Electro-Tech-Online.com
  • EE Learning Center
  • Video
    • EE Videos
    • TI Power Videos
    • Teardown Videos
  • Resources
    • Design Fast
    • eBooks / Tech Tips
    • FAQ
    • LEAP Awards
    • Podcasts
    • Webinars
    • White Papers

Review: Examining power and energy use with the Joulescope

February 14, 2019 By Lee Teschler Leave a Comment

The Joulescope is an inexpensive test instrument designed to let developers of embedded systems get a good look at the energy and power consumption of their hardware during important events such as interrupts and wake-up sequences. Developed by a company called Jetperch, Joulescopes are about to become available through a Kickstarter campaign launching Feb. 19.

joulescope connectionsJetperch recently loaned us a beta unit so we could get a feel for how the Joulescope works.
In a nutshell, the Joulescope connects between the power source and the power lines going to the target system, so it is basically in series with the target load. A key point about this connection is that most multimeters and current meters have a significant voltage drop which effects the actual voltage delivered to the device under test. But the Joulescope has a total voltage drop of 25 mV at 1 A, low enough to keep most target devices running correctly. And the Joulescope maintains the low voltage drop even under rapidly varying current demands.

joulescope
Joulescope power and target connections. The PC connection (USB) is on the other end of the enclosure.

Additionally, the Joulescope is optimized for measuring current consumption over a wide dynamic range. We easily viewed currents in the nanoamp range, and the device will accommodate targets consuming up to 10 A. A zooming function lets the user get a detailed view of tiny consumption levels.

The Joulescope generates a display through a USB connection to a PC which runs a Joulescope app. (A point to note: The Joulescope gets power through its USB connection. This power connection is isolated from the target power supply, a fact we didn’t check but which was verified in a review by Jack Ganssle of the Ganssle group.) There are two display modes, a DVM-like numeric display (averaged over each half second) of target current consumption, voltage, dissipated power and energy (the integration of power over time); and an oscilloscope-like real-time display of target-system supply voltage and current.

joulescope dvm display
The Joulescope’s DVM display. Statistics are at the right of the main read outs.

However, there’s an important difference between what a scope would display and what the Joulescope provides: The Joulescope also depicts a min and max level for voltage and current. These are useful because each of the pixels in the display are actually represented by multiple underlying samples. The min and max displays are the true min and max of the pixel level. So you don’t miss any min or max values in the supply line.

The Joulescope samples at a 2 Msps rate, high enough to make visible the power consumption of

current waveform
A typical current waveform (top) and voltage waveform (bottom) for a turn-on sequence as captured on the Joulescope display.

interrupt service routines, inrush currents, and similar events. The target device we used for checking out the Joulescope was an Arduino board containing an LED that flashed to give a varying current consumption.

As in the case of ordinary scope displays, you can zoom in on portions of a Joulescope display, but in the case of the Joulescope, you are truly zooming in rather than just changing the time base for a better look. (We found the display manipulations such as zooming and panning worked best with a mouse rather than a trackball controller.) Jetperch says it will be adding markers in an upcoming release of the Joulescope software that will let the user measure between specific points on captured waveforms in a way analogous to what’s possible on traditional scopes.

joulescope read out
This view of the scope-like display more clearly shows the max and min read outs for current and voltage. This view is basically a display of the noise on the output of the benchtop power supply we used to run the Arduino board.

The energy read-out is interesting. Besides giving the basic info, it also reads out statistics – min, max, standard deviation, and peak-to-peak – for each half-second interval. The point of the read-out for energy is for making comparisons. The typical scenario consists of getting an initial read-out of total consumed energy, making a change, and then looking at the new energy figure to see whether there’s an improvement. There’s also an accumulate button that lets the user accumulate data over more than the default half-second interval. This is useful for seeing peaks over some sequence of events.

Potential users of the Joulescope should be aware that its scope display doesn’t really trigger on a level or event as is usually the case with an ordinary scope. To view an event, the user reviews the contents of the Joulescope’s data buffer, typically about 30-seconds-worth of waveform capture. This effectively means you can’t turn on the Joulescope, leave to get a cup of coffee and come back to see what happened. You have to be peering at the screen to note something of interest is in the data buffer.

Other points of interest: The Joulescope comes equipped with banana jacks for the power and target connections, but the front panels are open source so these connections can be swapped for something else. The Joulescope software is also open source on GitHub, so presumably it should be possible to do some customization for specialized needs.

The Kickstarter campaign for Joulescope is set to kick off 2-19-19.

You may also like:

  • motor field-control
    Motor field-oriented control, Part 2: Implementation
  • LTR50 series chip resistors
    Wide-terminal, low-Ohm high-power thick-film chip resistors deliver top-notch TCR qualities

  • Power management ICs, part 1: PMIC functions
  • battery holders
    Maximizing efficiency and safety with rechargeable batteries
  • PowerSpot transmitter
    Development kit helps build power-over-distance wireless power transmitters

Filed Under: Development Tools, Featured, Power Supply News Tagged With: jetperch

Reader Interactions

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Primary Sidebar

DesignFast

Component Selection Made Simple.

Try it Today
design fast globle

Subscribe to our Newsletter

The Power Electronic eNewsletter delivers breaking electronic and power component news, resources, product innovations and more.

Subscribe today

Test & Measurement Handbook


EE TRAINING CENTER CLASSROOMS

“ee

“ee

“ee

“ee

“ee

RSS Current EDABoard.com discussions

  • Upconverting a 20 GHz signal to 28 GHz
  • Need simple Buckboost current source controller IC for 2A ...nothing exists?
  • Sine Wave Generation with SPI and TIM interrupt in STM32
  • Determining Polarity
  • How calculate PNP turn OFF resistor in BuckBoost converter?

RSS Current Electro-Tech-Online.com Discussions

  • Simple data logger with monitoring of a load on off time for 60 days
  • Simulation not outputting anything on LTSpice (asc file attached)
  • Tesla coil progress
  • QA pass
  • after few times programming debugger can't recognize microcontroller(stm32f101vbt6)

Follow us on Twitter

Tweets by PowerElectrTips

Footer

EE World Online Network

  • DesignFast
  • EE World Online
  • EDA Board Forums
  • Electro Tech Online Forums
  • Connector Tips
  • Microcontroller Tips
  • Analog IC Tips
  • Sensor Tips
  • Test and Measurement Tips
  • Wire and Cable Tips
  • 5G Technology World

Power Electronic Tips

  • Subscribe to our newsletter
  • Advertise with us
  • Contact us
  • About us
Follow us on TwitterAdd us on FacebookFollow us on YouTube Follow us on Instagram

Copyright © 2021 · WTWH Media LLC and its licensors. All rights reserved.
The material on this site may not be reproduced, distributed, transmitted, cached or otherwise used, except with the prior written permission of WTWH Media.

Privacy Policy