New: The Yocto-Meteo-V2

New: The Yocto-Meteo-V2

This week comes with a major refresh for one of our flagship products. We have been selling the Yocto-Meteo for almost 7 years, and the quality of the sensors embedded on this device has made its success. Now comes the time when the key sensor is getting replaced by the manufacturer by an even more accurate version. So it is time to update our product as well...


A bit of history

The original Yocto-Meteo was put on the market in January 2012, featuring a Sensirion SHT21 humidity and temperature sensor, and a Freescale MPL115A2T1 pressure sensor. The price was of about 61 CHF (i.e. 51 EUR or 66 USD).

A few years later, Sensirion came out with an updated version of the SHT21 sensor named SHT25, which is actually the same sensor but with a better calibration. Similarly, Freescale also came out with an updated MPL3115A2 with a better accuracy. The Yocto-Meteo was therefore upgraded to use these improved versions of the sensors. There was no price increase, as we were able to balance the higher sensor price with the price decrease on other components, as our volumes were increasing. In 2017, thanks to the new sensor price going down, we were even able to reduce the Yocto-Meteo price to 51 CHF.

The Yocto-Meteo V2

The new version that we present today is a more in depth evolution than the first precision leap: the brand new SHT35 humidity sensor uses a different technology, different voltage, different protocols. The new ICP10100 pressure sensor is made by TDK InvenSense instead of Freescale. The precision increase is also more important, and significantly enlarges the range of environmental conditions in which the sensors provide accurate measurements, as illustrated in the section below. So this makes for a new major release of the product.

On the left: Yocto-Meteo, on the right: Yocto-Meteo-V2
On the left: Yocto-Meteo, on the right: Yocto-Meteo-V2


The good news is that for our users, these changes are completely transparent. We have designed the Yocto-Meteo-V2 to be 100% compatible with its predecessor. Products designed to work with the Yocto-Meteo will also work with a Yocto-Meteo-V2, in most cases without even recompiling them. Even the physical location of the sensor as been preserved, in case that matters for the physical design of your system. The only functional difference between both products is the improved accuracy of measurements provided by the Yocto-Meteo-V2.

Both the SHT35 and the ICP10100 are now watertight, which means they will not be damaged by water. The Yocto-Meteo-V2 electronics may still need tropicalization if you want to splash it with water, but if you protect both sensors adequately during tropicalization, you can then expose them directly to water without damage.

Of course, these new goodies have a price, and the new sensors cost more than the older ones used in the Yocto-Meteo. But we are able to offer the Yocto-Meteo-V2 with only 10% price increase compared to the current Yocto-Meteo, which is even less than the original pricing of the Yocto-Meteo 7 years ago.

Comparison of accuracy

Let's see how both versions compare in terms of accuracy. First comparison: accuracy of the humidity measurement at 25C:


Yocto-MeteoYocto-Meteo-V2

Tolerance of RH at 25C for SHT25
Tolerance of RH at 25C for SHT25

Tolerance of RH at 25C for SHT35
Tolerance of RH at 25C for SHT35


This shows that although the typical uncertainty is reduced by 15% for standard conditions, the most significant improvement is in very dry or very wet conditions, where the reading is now significantly more reliable. This is even clearer when looking at the typical accuracy over both humidity and temperature conditions:


Yocto-MeteoYocto-Meteo-V2

Typical tolerance of RH over T for SHT25
Typical tolerance of RH over T for SHT25

Typical tolerance of RH over T for SHT35
Typical tolerance of RH over T for SHT35


There is also a significant improvement on the accuracy of the temperature measurement itself, which is now typically accurate up to 0.1C in standard conditions, and to 0.2C on the whole extended temperature range of the Yocto-Meteo-V2 (-30C to 85C). This improvement matters in particular for applications that use of the absolute humidity (in g/m3) rather than the relative humidity, since the conversion from relative humidity to absolute humidity performed in the Yocto-Meteo-V2 involves the current temperature as well.


Yocto-MeteoYocto-Meteo-V2

Tolerance of temperature for SHT25
Tolerance of temperature for SHT25

Tolerance of temperature for SHT35
Tolerance of temperature for SHT35


Note that in order to obtain such a high absolute accuracy, you need to carefully position the sensor to avoid any heat from the electronics itself to reach the sensing part.

Last but not least, switching from the Freescale pressure sensor to the TDK InvenSense pressure sensor, we have been able to provide a huge improvement in the accuracy of the pressure measurements. For those of you who need to measure the pressure below -10C, this will make a real difference in terms of reliability of the absolute value.


Yocto-MeteoYocto-Meteo-V2

Typical absolute accuracy over T for MPL3115A2
Typical absolute accuracy over T for MPL3115A2

Typical absolute accuracy over T for ICP10100
Typical absolute accuracy over T for ICP10100


When an even higher accuracy is required, a one-point calibration can actually easily improve the accuracy to another level, as the new sensor has an impressive stability and repeatability of 0.01 mbar during a 10 mbar variation between 950 and 1050 mbar. That will surely qualify it to make a Yocto-Altimeter-V2, stay tuned...

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