{"id":238628,"date":"2021-06-18T12:24:41","date_gmt":"2021-06-18T10:24:41","guid":{"rendered":"https:\/\/emariete.com\/?p=238628"},"modified":"2021-06-18T12:24:41","modified_gmt":"2021-06-18T10:24:41","slug":"sensor-co2-sensirion-scd40-scd41","status":"publish","type":"post","link":"https:\/\/emariete.com\/en\/sensor-co2-sensirion-scd40-scd41\/","title":{"rendered":"Sensirion SCD41 and SCD40 CO2 Sensors"},"content":{"rendered":"

Do you want a small CO2 sensor, from low consumption, versatile and high quality<\/strong>The Sensirion SCD40 and SCD41 are for you!<\/p>\n\n\n\n

It is quite likely that the Sensirion SCD41 CO2 sensor<\/strong> (and its twin, the SCD40) is the sensor you are looking for.<\/p>\n\n\n\n

<\/p>\n\n\n\n

In this article I bring you an analysis, together with my first impressions<\/strong>Sensirion SCD41 and SCD40 sensors.<\/p>\n\n\n\n

Sensirion is a Swedish manufacturer<\/strong> with a long experience<\/strong> in the production of quality CO2 sensors. Its sensor SCD30<\/strong>a dual channel NDIR sensor<\/strong><\/a>has been a benchmark for the last few years. A clear favourite when it came to a quality sensor at an acceptable price.<\/p>\n\n\n\n

Recently, during the second quarter of 2021<\/strong>Sensirion has surprised us by adding new members to the CO2 sensor family<\/strong>the SCD40 and SCD41<\/strong>.<\/p>\n\n\n\n

What makes the Sensirion SCD40 and SCD41 sensors special?<\/h2>\n\n\n\n

The truth is that just look at it<\/strong>. What makes these sensors special it enters through the eyes<\/strong>.<\/p>\n\n\n\n

The first thing that strikes you about this sensor is its tiny size. Only 10.1 x 10.1 x 6.5 mm<\/strong>unbelievable. <\/p>\n\n\n

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But this sensor is much more than a pretty face on a slim body<\/strong>... offers characteristics, on paper, that is in no way inferior to sensors of a much larger size (and power consumption).<\/strong>with little or no sacrifice.<\/p>\n\n\n\n

The Sensirion SCD40 and SCD41 CO2 sensors are high-performance sensors<\/strong>.<\/p>\n\n\n\n

What is the difference between the Sensirion SCD40 and SCD41?<\/h2>\n\n\n\n

These two sensors are virtually the same<\/strong>are twin brothers.<\/p>\n\n\n\n

Externally, the two sensors look the same, but internally they are two different beasts<\/strong>.<\/p>\n\n\n\n

That said, the major differences are to be found in its measuring range and consumption<\/strong>.<\/p>\n\n\n\n

The Sensirion sensor SCD40 <\/strong>can measure CO2 concentrations from 400 to 2000 ppm and has a typical consumption of 15mA at 3.3V or 11mA at 5V<\/strong>.<\/p>\n\n\n\n

The SCD41 <\/strong>and can also measure a wider range, from 400 to 5000<\/strong> ppm, has a Typical minimum power consumption of only 0.45mA at 3.3V and 0.36mA at 5V.<\/strong>This allows us to create CO2 meters with great autonomy.<\/p>\n\n\n\n

To achieve this low power consumption, the SCD41 has a \"single measurement\" mode of operation, called \"single measurement\". \"single shot mode<\/strong> where the sensor is used on demand to take a single measurement (the above consumption is that corresponding to a measurement every 5 minutes).<\/p>\n\n\n\n

How did Sensirion achieve such a small sensor?<\/h2>\n\n\n\n

Sensirion's secret to achieving this small size has been to use a technology other than NDIR<\/strong> to which we are accustomed, while maintaining its high quality of measurement, has created a sensor for the electro-acoustic technology<\/strong>.<\/p>\n\n\n\n

What is an electro-acoustic CO2 sensor?<\/h2>\n\n\n\n

In the NDIR sensors that we usually use, the operation is based on the absorption <\/strong>that CO2 is on an infrared beam<\/strong>. <\/p>\n\n\n\n

In an NDIR sensor there is an infrared emitter and a sensor that detects infrared. The more CO2 there is between the infrared emitter and the sensor that detects it, the less infrared the sensor detects.<\/strong>.<\/p>\n\n\n\n

Electro-acoustic sensors are based on the effects that the CO2 concentration produces in sound waves<\/strong>.<\/p>\n\n\n\n

Electro-acoustic measuring principle<\/h3>\n\n\n
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In an almost completely closed measuring chamber, a narrow-band light is emitted that coincides with the wavelengths that are absorbed by the CO2 molecules.<\/strong>. <\/p>\n\n\n\n

CO2 molecules in the measuring chamber absorb a part of the radiated light<\/strong>while other molecules do not contribute to absorption due to the spectrum of the emitted light. <\/p>\n\n\n\n

How many more CO2 molecules<\/strong> in the measuring cell, the more energy absorbed<\/strong>. <\/p>\n\n\n\n

The energy absorbed from the CO2 molecules excites mainly the molecular vibrations<\/strong>which gives rise to a increase in the translational energy of molecules<\/strong> and, due to the enclosed measuring chamber, to a increase of pressure in the chamber<\/strong>. <\/p>\n\n\n\n

A modulation of the light source causes a periodic pressure change in the measuring cell, which can be measured with a microphone. The signal of the microphone thus serves to measure the number of CO2 molecules present in the chamber.<\/strong> measurement<\/strong> and can be used to calculate the CO2 concentration.<\/p>\n\n\n\n

Sensirion calls its implementation of this technology PASens\u00ae Technology<\/strong>.<\/p>\n\n\n\n

How much does a Sensirion SCD40 or SCD41 cost?<\/h2>\n\n\n\n

The truth is that this has meant a real surprise<\/strong>especially when compared to ultra-low power sensors.<\/p>\n\n\n\n

We are used, especially the makers, to buying our sensors in China, on sites such as AliExpress, and that makes it easier for the prices to be much lower than in the official marketing channels.<\/p>\n\n\n\n

For example, the SCD30 sensor in an official distributor such as Mouser, costs approximately 55\u20ac. This same sensor, as you can see in this link Sensirion SCD30 on AliExpress<\/a> (same link where I bought it and it took me only 7 days to arrive), it costs about 35\u20ac.<\/p>\n\n\n\n

Well, the SCD40 costs about 36\u20ac at Mouser and the SCD41 47\u20ac for one unit (you get good discounts for quantity). If we compare it with the price of the SCD30 in China, if we could buy the SCD41 on AliExpress (it's not available yet, I'll let you know here when it is, if you see it before let me know), it would cost around 25\u20ac or less.<\/p>\n\n\n\n

In addition, for applications where good battery life is needed, this sensor is significantly cheaper than other ultra-low-power sensors, such as the Senseair Sunrise S11 (which costs about 55\u20ac at Digikey) and the Cubic CM1106SL-NS (which is not even readily available but is expected to be priced similarly to the Senseair Sunrise S11).<\/p>\n\n\n\n

The Sensirion SCD41 development kit<\/h2>\n\n\n\n

These sensors are not all advantages. <\/p>\n\n\n\n

One disadvantage for makers is that this miniaturisation has a side effect: to achieve such a compact size, Sensirion has used a QFN encapsulation<\/strong>which complicates things quite a bit because we will need a custom printed circuit board<\/strong> and make some welds that are quite difficult to perform<\/strong> for the average amateur.<\/p>\n\n\n\n

Fortunately, if we do not want to weld it ourselves, we have a solution that comes to our rescue: The development kit.<\/strong>.<\/p>\n\n\n

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The development kit is nothing more than the sensor SCD41 or SCD40, soldered to a small printed circuit board<\/strong> customised with connectors, terminals and cable to make it easier to tinker <\/strong>with the sensor.<\/p>\n\n\n\n

Of course, it's not all advantages, if we decide to use the \".Evaluation Kit SEK-SCD41<\/em>\"We are going to meet with:<\/p>\n\n\n\n