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AmpeROSE Week 2: The First Presentation

Hello, everyone!

Here is an update for the AmpeROSE project:

The First Presentation

For this week, our main mission was to prepare an initial presentation of our project to be done before our teachers and colleagues. The presentation had to cover five essential aspects:

  • What is our goal with this project, and what are the use cases we envision for it?
  • What are the main features of the project?
  • What are the the technical limitations our project will suffer from?
  • What are our Project Specific Success Criteria (PSSC)? These are a series of simple “yes or no” (or “done or not done”) questions, each corresponding to a step in the design and construction of the AmpeROSE device, such that a step will only be considered complete if  the corresponding PSSC may be answered affirmatively.
  • Which technologies will be used for data communication in the project?

Thinking about these questions really helped make the AmpeROSE device more concrete to us. Here are the answers we have at this point, to a lesser or greater degree, they are all likely to evolve as the project goes on:

Goals

Our goal with ampeROSE is to build a prototype for an affordable digital ammeter that integrates naturally with the conception of low-power connected objects. The ammeter will be placed between the battery and the device under test, and transmit the measurement data to a computer, where an user interface makes it possible to visualize the data and treat it (for instance, with some of the usual options found in a digital oscilloscope: FFT, integration, trigger options, determinations of min and max values…).

Main Features

The main features are similar to what was described in the previous post about AmpeROSE:

  • High sampling rate (at least 1MHz).
  • A dynamic range going from 10nA to 100mA.
  • Self-calibration.
  • Data transfer to a host pc.
  • A simple and effective user interface.

Technical Limitations

An important technical limitation is that the measurements with AmpeROSE will necessarily be intrusive to some degree to the normal operation of the device under test. Our challenge is then to diminish this intrusiveness as much as possible, so the measurements are as accurate to the real values as possible.

PSSC

We structured our PSSC around five main themes:

  • Current Measurement: the design and implementation of the analog circuitry used to measure the current being drawn from the battery by the device under test, and how it will interface with the digital part of AmpeROSE.
  • Data Processing: the design and implementation of the digital part of AmpeROSE (selelection of the embedded processor, development of the firmware…)
  • Circuit Board: The design and implementation of the circuit board which will house both the digital and analogic composants of AmpeROSE.
  • Packaging: The conception of the 3d-printed packaging that will house the circuit board.
  • User Interface: The development of the program that communicates with AmpeROSE, through which the user will be able to access the data collected by the ammeter.

Communication Technologies

We are still considering USB 2, USB 3 and Ethernet as options for connecting AmpeROSE to the computer hosting the user interface (or even having two or three of technologies as options to the user). A question that must be answered before we can reach a decision is whether the bit rate that will be required for transmitting the measurements to the user interface is compatible with even USB 2. Some back-of-the-envelope calculations suggest it should be, but we really need to determine this more formally, which leads us to:

Numbers, numbers, numbers…

For this new week, the first goal (indeed, to be completed by the end of monday morning) is to augment our description of our project with informed estimations of all the key quantities related to it:

  • What computing power will be demanded from the embedded processor within AmpeROSE (multiplication / additions per second…)
  • How much measurement data AmpeROSE should able to store internally at any given time.
  • What bit rate will be required for the communication between the AmpeROSE device and the computer hosting the user interface (as mentioned)

And most important of all:

  • etc.

This exercice will be essential in order to proceed to the selection of specific components for AmpeROSE. Check in next week to learn what conclusions we reached!

2 comments to AmpeROSE Week 2: The First Presentation

  • phh

    Hi,

    > The ammeter will be placed between the battery and the device under test
    I’m a bit curious about this.
    Does this mean you’ll have a precise/fast volt-meter integrated as well?
    This would be cool, because calibrating correctly a battery is far from easy,
    your tool would help that as well 🙂

    Also, does this mean that AmpeROSE won’t influence the current/voltage either on the DUT and the battery?
    Or will you accept some loss on battery side, as long as DUT measurement is good?

    > A dynamic range going from 10nA to 100mA.
    I guess you’ve already checked, but 100mA feels a bit low to me.
    For instance, how much does the Stealth Drop is expected to peak at?

    I can’t wait for your posts about your exploration of how to do AmpeROSE 🙂

  • MichelElHABR

    Hello phh,
    Thank you for the comment!

    I’m afraid a voltmeter probably won’t be integrated within the AmpeRose device.

    As for the voltage drop (or burden voltage), we are comparing measuring methods
    to minimize it. We will soon post some updates concerning the theoretical
    values of the burden voltages for the different methods.

    Finally, concerning the maximum measured current, we have decided to up this value from 100 mA to 1 A.
    This should accommodate a greater number of IoT devices.

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