Joulescope JS220 User manual

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Joulescope™JS220 User’s Guide
Precision DC Energy Analyzer
Revision 1.3
Last revised 2022 October 25

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1. Affordable, easy-to-use, accurate and precise
Multimeter view
Oscilloscope view
Applications include:
•Microprocessor and microcontroller power profiling and optimization
•Hardware power optimization
•Microcontroller and device sleep current optimization
•Hardware and software troubleshooting
•Software characterization and interrupt service routine profiling
•USB inrush and suspend current pre-compliance testing
•General-purpose current, voltage, power, charge, and energy measurement
The Joulescope™JS220 is the most affordable and easy-to-use precision DC energy analyzer. It
measures current and voltage, then computes power and energy. Many modern battery-powered
devices and IoT devices have a high dynamic current range, which makes accurate measurement
difficult. When “sleeping” the devices consume nanoamps (nA) or microamps (µA), but when active,
they consume milliamps (mA) or amps (A). Joulescope combines high-speed sampling and rapid
dynamic current range switching to provide accurate and seamless current and energy measurements,
even for devices with rapidly varying current consumption. The unprecedented accuracy and low-cost
of Joulescope allows every engineer on the team to measure the energy consumed by the target device
during development. Joulescope provides rapid feedback on how changes affect the overall product
battery life.
Joulescope displays instantaneous voltage, current, power, and energy, like a multimeter. The
multimeter provides a quick and easy summary of the present state of your device.
Joulescope displays waveforms of voltage and current over time, like an oscilloscope. This oscilloscope
view allows you to identify and to troubleshoot dynamic behavior and short events, including inrush
current, event handlers, and tasks.

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2. Key benefits
•Dynamic range: The Joulescope JS220 accurately measures electrical current over ten orders of
magnitude from amps down to nanoamps. This wide range allows accurate and precise current
measurements for modern devices. Sleep modes are often just nanoamps (nA) or microamps
(µA). Active modes are often milliamps (mA) or amps (A).
•Low voltage drop: Most multimeters and current meters have a significant voltage drop
(sometimes called burden voltage or insertion loss), which affects the actual voltage delivered to
the device under test. Joulescope has a total voltage drop of 25 mV at 1 A, which keeps your
target device running correctly. Joulescope’s extremely fast current range switching maintains
low voltage drop even under rapidly varying current demands.
•Makes the invisible visible:The JS220 measures current and voltage 2 million times per second
with 300 kHz bandwidth. This high sampling rate makes the power consumption of interrupt
service routines, inrush currents, and other short events visible.
•Easy to use:The JS220 reports cumulative energy and charge consumption along with real-time
current, voltage, and power. The multimeter view clearly shows the most recent value, while
the oscilloscope view allows you to explore changes over time. Much simpler and more
accurate than anything in its class!
•Customizable: The host software is open source on GitHub. You can also swap the banana jack
front panel with front panels that have other connector types. The front panels are open source
on GitHub.
•Portable: The JS220 fits in your backpack and only needs a small part of your desk. It provides
precision measurements in a portable, unintrusive form factor.
•Affordable: The Joulescope JS220 is affordable and priced so that every developer on the team
can have one at their desk. With such convenient access, Joulescopes allow developers to see
the impact of their changes on energy consumption immediately. Developers can make
informed choices to account for battery life during design. Eliminate power consumption
surprises during final product testing!

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3. Key features
•±15V voltage range
•±3A current range, continuous
•±10A current pulses (<10 ms, < 3A average per second)
•Down to 0.5 nA resolution, equivalent to 34-bits of dynamic range
•Synchronously measures voltage and current at 2 million samples per second, 16-bit
•300 kHz bandwidth
•Rapid 1 μs switching between shunt resistors
•Enwavify™technology for consistent, accurate measurements through current range changes
•Computes power, energy, and charge
•Operates with minimal voltage disturbance between Current + and Current –ports
•Up to ±48V common-mode voltage between USB ground and sensing ports
•4 general-purpose inputs and 2 general-purpose outputs
•1 BNC trigger configurable for either input or output
•Programmable on/off for power cycling the target device and measuring inrush currents
•USB 2.0 high-speed host connectivity with modern USB C connector
•Host software support for Microsoft® Windows®, Apple® macOS®, and Linux®
•Host software user interface provides real-time graphs of current, voltage, and power over time
•Python library and scripting provided
•Host software is open source and available on GitHub
•Swappable front panel with open-source designs on GitHub
•Firmware upgradable
See Section 7 for the full specifications.

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4. Table of contents
1. Affordable, easy-to-use, accurate and precise .....................................................................................2
2. Key benefits...........................................................................................................................................3
3. Key features ..........................................................................................................................................4
4. Table of contents ..................................................................................................................................5
5. Meet Your Joulescope JS220.................................................................................................................8
6. Quick start...........................................................................................................................................11
7. Specifications ......................................................................................................................................13
7.1. Absolute maximum ratings.........................................................................................................13
7.2. Mechanical..................................................................................................................................13
7.2.1. Instrument Only..................................................................................................................13
7.2.2. Complete product kit ..........................................................................................................13
7.3. Recommended operating conditions..........................................................................................14
7.4. Specification conditions..............................................................................................................14
7.5. Current measurement specifications..........................................................................................14
7.6. Voltage measurement specifications..........................................................................................14
7.7. General specifications.................................................................................................................15
7.8. Parasitic effects specifications....................................................................................................15
7.9. Software-controlled fuse specifications .....................................................................................15
7.10. General Purpose Inputs & Outputs.........................................................................................15
8. Host software......................................................................................................................................17
8.1. Installation ..................................................................................................................................17
8.1.1. Linux....................................................................................................................................17
8.1.2. Windows .............................................................................................................................17
8.1.3. macOS .................................................................................................................................17
8.2. Multimeter view .........................................................................................................................17
8.3. Oscilloscope view........................................................................................................................19
8.4. Energy and Charge......................................................................................................................22
8.5. Open-source................................................................................................................................22
9. How to Connect Your Joulescope .......................................................................................................24
9.1. Measure only current (ammeter) ...............................................................................................24
9.2. Measure only voltage (voltmeter) ..............................................................................................25
9.3. Measure power supply provided................................................................................................26

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9.4. Measure target device consumption..........................................................................................28
9.5. Measure subsystem consumption..............................................................................................29
10. Theory of operation........................................................................................................................31
10.1. Ammeter .................................................................................................................................31
10.2. Voltmeter................................................................................................................................32
10.3. Host Computer........................................................................................................................32
10.4. Power, Energy, Charge, and Statistics.....................................................................................32
10.5. High impedance / low leakage................................................................................................33
10.6. Electrical isolation...................................................................................................................33
11. How to swap the front panel ..........................................................................................................34
12. GPI & GPO .......................................................................................................................................35
13. Electrical Isolation...........................................................................................................................37
14. Typical Behavior..............................................................................................................................38
14.1. Step Response.........................................................................................................................38
15. Maintenance...................................................................................................................................39
15.1. Verification Procedure ............................................................................................................39
15.1.1. Preliminary operations........................................................................................................39
15.1.2. Voltage Validation Process..................................................................................................39
15.1.3. Current Validation Process..................................................................................................40
16. Compliance .....................................................................................................................................43
16.1. United States...........................................................................................................................43
16.1.1. FCC Compliance Statement.................................................................................................43
16.1.2. FCC Notice...........................................................................................................................43
16.2. Canada ....................................................................................................................................43
16.3. Europe.....................................................................................................................................43
16.4. Safety ......................................................................................................................................44
16.5. RoHS Directive 2011/65/EU, 2015/863/EU ............................................................................44
16.6. Country of origin .....................................................................................................................44
17. Warranty.........................................................................................................................................45
18. Intellectual Property .......................................................................................................................46
19. Contact............................................................................................................................................47
20. Glossary...........................................................................................................................................48
21. User’s guide information ................................................................................................................50

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21.1. Copyright notice......................................................................................................................50
21.2. Publisher .................................................................................................................................50
21.3. Warranty .................................................................................................................................50
21.4. Change log...............................................................................................................................51

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5. Meet Your Joulescope JS220
The JS220 arrives in a carry case:
Unzip the carry case to find the JS220 instrument and accessories:

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Your Joulescope JS220 purchase includes:
•Joulescope JS220 instrument with factory calibration
•Binding Post Front Panel, already installed
•5’ USB 2.0 A to C cable
•GPIO cable assembly
•2 mm Allen wrench, for optionally swapping the front panel
•Quick Start Guide
•Joulescope sticker
•Carry case
You will need to provide:
•A host computer running Microsoft® Windows® 11 or 10, Apple® macOS® 12 or 10.15, or Linux®.
Most computers manufactured within the last five years should work. The computer requires
an available USB 2.0 port, at least 500 MB of hard drive / solid state drive storage space, and 1
GB of available RAM.
•Suitable cable(s) to connect the Joulescope JS220’s binding posts to your system, often the
power source and device under test.
•For computers without USB A ports, a suitable USB cable or USB adapter.
•Optional BNC cable for connecting trigger to other equipment.
You need an internet connection to download the free software.
The front side of the JS220 has the connectors that connect to your system:
Your JS220 measures the voltage across the Voltage + and Voltage –binding posts. Your JS220 measures
the current flowing through the Current + to the Current –binding posts. If you have a power source
and target device, connect the positive side through the current binding posts. You can then connect
the voltage signals across either your power source or your target device. For more connection
examples, see Section 9.
The Sensor Status indicator is off when your JS220 is powered off or inactive. Flashing red indicates that
the instrument is ready but the current flow is not yet enabled. Solid green indicates that current
measurement is enabled.

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The backside of Joulescope has the host USB connector, status LED, GPIO connector, and trigger
connector:
Use the provided USB C to USB A cable to connect the USB host computer connector to your host
computer. If your computer only has USB C ports, use an adapter (not provided) or a USB C to USB C
cable (not provided).
The Controller Status indicator is off when the JS220 is not connected to the host computer, or the host
computer has not yet activated the JS220 over USB. Microsoft Windows computers activate devices
immediately when connected while macOS and Linux do not active the device until the Joulescope
software attempts to use the device. Solid blue indicates that the JS220 is activated. Solid green
indicates that the JS220 device is running normally.
The GPIO connector provides four general-purpose inputs and two general-purpose outputs. See
Section 12 for details.
The BNC Trigger connector provides either a Trigger Out or a Trigger In. This Trigger allows the JS220 to
synchronize data collection with other equipment.