This device is a digital watt-meter allowing to monitor power consumption of electrical device. Its works with both AC and DC current. Regarding AC current, the device compute the real power consumption (not just the product of RMS voltage and current), so it can be used to monitor inductive loads. The Yocto-Watt can compute the poser consumption during a given lapse of time. Accuracy will be 1mWh, 1%.

This device is isolated, which means that the sensing part is electrically disconnected from the USB part: you can measure any voltage difference between -250V and 250V, without risk of frying your computer.
The modules provides immediate reading on USB, and can also store measures on the device internal flash for later retrieval when connected again by USB.

This device can be connected directly to an Ethernet network using a YoctoHub-Ethernet, to a WiFi network using a YoctoHub-Wireless-g, it can even be connected to a GSM network thanks to the YoctoHub-GSM.

Yocto-Watt Yocto-Watt Yocto-Watt

USB cables and enclosure to be ordered separately.

CHF 94.50

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Manufacturer Product NumberYWATTMK1
Product nameYocto-Watt
USB connectormicro-B
Max current (Cont.)16A
Refresh rate10Hz (DC)
Max voltage250V
Accuracy (AC)0.2 W / 3%
Accuracy (DC)0.002 W / 1.5%
Supported Operating SystemsWindows, Linux (Intel + ARM), Mac OS X, Android
Driversno driver needed
API / SDK / Libraries (USB+TCP)C++, Objective-C, C#, VB .NET, Delphi, Python, Java/Android
API / SDK / Libraries (TCP only)Javascript, Node.js, PHP, Java
Suggested enclosureYoctoBox-Watt-Black
Made inSwitzerland

Related articles and application examples

 New product: the Yocto-Watt  Yocto-Boom  What happens inside the fridge? 

Accessories and related products

YoctoBox-Watt-Black, Plastic enclosure for the Yocto-Watt sensorYoctoBox-Watt-Transp, Plastic enclosure for the Yocto-Watt sensorUSB-A-MicroB-30, A to micro-B USB data cable, 30cm


User manual (HTML)
User manual (PDF)
3D file (STEP)
Last Firmware24473 (06/20/2016)
Library for Javascript25534 (10/10/2016)
Library for PHP25534 (10/10/2016)
Library for Objective C25534 (10/10/2016)
Library for C++25534 (10/10/2016)
Library for C#25534 (10/10/2016)
Library for VisualBasic .NET25534 (10/10/2016)
Library for Delphi25534 (10/10/2016)
Library for Python25534 (10/10/2016)
Library for Java25534 (10/10/2016)
Library for Android25534 (10/10/2016)
Library for Command line25250 (08/23/2016)
Virtual Hub for Windows25601 (10/19/2016)
Virtual Hub for Linux, Intel + ARM25601 (10/19/2016)
Virtual Hub for Mac-OS-X25601 (10/19/2016)

Add a comment 16 comments

1 - funky81 Sunday,may 19,2013 8H38

Currently, I'm planning to buy YoctoWatt to monitor all the wattage in my house. I subscribe for 2200KWH.

Will this thing work ?

2 - martinm (Yocto-Team)Sunday,may 19,2013 8H59

@funky81: actually the 22000kWh value is not sufficient to answer: is it per month? The decisive parameter is the Amp peak. The Yocto-Watt limit is 16Amp. Note that at 16 Amp continuous , the shunt on the board will get pretty hot (~100░C). Beyond this limit, the device will become a fire hazard.

So I wouldn't use just one single Yocto-Watt for the whole house. I would use, lets say, one Yocto-Watt per circuit, and I would make sure they are properly cooled.

Also note that Yoctopuce devices are not certified (see Yoctopuce's General Terms & Conditions).

3 - funky81 Tuesday,may 21,2013 22H20

Yup, thats 2200KWH per month. Currently, my house current stable at 7.8Amp.
Since this below 16Amp, will it be sufficient enough to use this product?
Anyway, let me check how many circuit my house have.


4 - martinm (Yocto-Team)Friday,may 24,2013 6H03

@funky81: With 7.8Amp avg you seem to be the safe side. Nevertheless you still need to check for peak consumption. Install your Yocto-Watt and switch on as many big equipment as you can. Check that the total consumption is below 16A. You also need to make sure the Yocto-Watt temperature stay reasonable. DO NOT touch it to check, use a infrared-thermometer or install a Yocto-Temperature in the same enclosure.

5 - blacksmith Tuesday,june 04,2013 13H26

I'm looking for some indication of the storage capacity and the interval the values can be stored. What place can I find this?

6 - mvuilleu (Yocto-Team)Tuesday,june 04,2013 14H33

@blacksmith: You can find this in the user manual, Chapter 19 section 2 (see http://www.yoctopuce.com/EN/products/yocto-watt/doc/YWATTMK1.usermanual.html#CHAP19SEC2 ). The Wattmeter can store up to 500'000 measures. Since each data sample stores 5 measures (DC voltage, AC voltage, DC current, AC current and power), it means you can store 100'000 data samples.

7 - RB Wednesday,may 27,2015 11H19

I have a Solar Charge Controller and I'd like to see how much output my PV (12v 40W) is providing, what my draw on the load is and what capacity my battery is at.

To do this, would I have to purchase 3 of these units, or is there a better product?


8 - martinm (Yocto-Team)Wednesday,may 27,2015 11H36

@RB: One single Yocto-Watt can do all this at the same time.

9 - RB Wednesday,may 27,2015 11H58

@martinm How is that possible as there is only a single Input/Output?


10 - martinm (Yocto-Team)Wednesday,may 27,2015 14H09

@RB: There might be a little misunderstanding here: The Yocto-Watt can give the Voltage, Current, Power, and perform Power integration on a electric connection. If you need to monitor several connections, you will need several devices.

11 - jirkasi Wednesday,january 20,2016 10H55

Hello i need scan instant power comsuption to motor 0,5 kW 230V every half second. Would this work with Your Yocto-
watt device?

12 - mvuilleu (Yocto-Team)Wednesday,january 20,2016 16H00

@ jirkasi: Yes, that should be no problem

13 - southerner Tuesday,april 19,2016 17H44

I have to measure AC loads which peak 50A. May I use a current transformer, as with other instruments?

14 - mvuilleu (Yocto-Team)Wednesday,april 20,2016 9H11

@southerner: you can use a current transformer, but be aware that CT will add a small phase shift, which will slightly alter the measure of power. A good CT has a phase shift of only a fraction of degree, which will have no significant impact, but a cheap CT may have several degrees of phase shift.

15 - mmoram Friday,september 23,2016 7H31

Hi, I would like to measure the power consumption of a mobile phone and of a single board computer (Odroid), would the Yocto-Watt be good for this application? I used an ammeter before inserting it in between the phone and the battery, but I would like to obtain power measurements

16 - mvuilleu (Yocto-Team)Friday,september 23,2016 8H36

@mmoram Yes, that is a typical use for this product

Yoctopuce, get your stuff connected.