Sensirion, the “Sensor Company” and the “Experts in Environmental Sensing”, has introduced their new SGP30 digital, long-term stable, multi-pixel gas sensor for indoor air quality applications. What exactly does the acronym “SGP” stand for? Well…I haven’t been able to find that bit of information. Using acronyms for products without actually stating what said acronyms mean has always been a pet peeve of mine. However, Sensirion has done an excellent job in providing educational material regarding their sensors and associated terminology.
For instance, their term “multi-pixel” is borrowed from their “multi-pixel platform” which, according to their site, “integrates four gas sensing elements into a very small 2.45 × 2.45 × 0.9 mm3 DFN package featuring a fully calibrated air quality output signal.”
A package that measures 2.45mm × 2.45mm is indeed an impressively very-small package, especially considering the capabilities of this gas sensing device, which include providing VOC and TVOC levels.
VOC and TVOC
What, you might ask, are the acronyms VOC and TVOC, and why are they important? Well, fortunately, Sensirion has provided some answers. “VOCs” stands for “volatile organic compounds”, which originate from new products and building materials, such as new carpet and furniture, paints and solvents, and cleaning agents. And according to Sensirion, total VOC (or TVOC) “refers to the total concentration of VOCs present simultaneously in the air”; it’s a quick and cost-effective way to assess indoor air quality. The image below provides some TVOC levels and recommendations.
Figure 2. TVOC levels and recommendations. Image courtesy of Sensirion (PDF).
Fortunately, and probably not coincidentally, the SGP30’s output range covers all these TVOC levels (see figure below).
Figure 3. SGP30 TVOC range. Image courtesy of SGP30 brochure (PDF).
Features and Benefits of the SGP30
The SGP30 is intended for air purifiers, demand-controlled ventilation, and various IoT applications. I wonder, given its small size, long-term stability, and digital interface, if this sensor (or others like it) will find its way into smartphones—turning your phone into something like a tricorder.
And speaking of long-term stability, apparently, according to the graph below, similar traditional gas sensors seem to lose their stability and accuracy after only a few months due to the chemical compound siloxane.
Figure 4. Simulated operation time in an indoor environment based on accelerated lifetime measurements. Image courtesy of this SGP flyer (PDF).
Supply Current in Measurement Mode
Table 3 states that the supply current in measurement mode has a typical value of 48.2mA, with no maximum value being listed. This is some serious current—an entire microcontroller might consume less than 1 mA when operating at a low clock speed. This sensor may be intended for IoT applications, but I would say that it is much more suitable for non-battery-powered IoT devices.
Also, don’t overlook footnote 6 that states, “A 20% higher current is drawn during 5ms on VDDH after entering the measurement mode.” Why not just list this higher current requirement as a maximum current? A 20% increase can be quite significant even if it’s only for 5ms.
Generally speaking, I’m a fan of parts that are easy to implement, and the SGP30 is one of those parts. All that’s required, for adding this IC to a design, is one external bypass capacitor and two pull-up resistors for the I2C bus.
Figure 5. Typical application circuit—only three external components are needed. Image courtesy of the SGP30 datasheet (PDF).
Also, Sensirion has provided (in section 8.4 of the datasheet) valuable information related to the IC’s landing pattern.
Some Documentation Goofs and Areas for Improvement
For the most part, I find the SGP30 datasheet and other supporting documentation to be very helpful and educational. However, I find it interesting, as noted in Table 7 (Communications Timing Specifications), that the minimum I2C clock frequency (SCL clock frequency) is 0 Hz. Really? I’m pretty sure at 0 Hz there will be no I2C communications.
Also, it would be helpful if hyperlinks were provided for the documents “SGP Handling and Assembly Instructions” and “Design-in Guide for Optimal Integration of the SGP30”, both of which are referenced in Section 1.3 of the datasheet. However, this datasheet is marked as preliminary, and perhaps Sensirion is still working out the kinks in their documentation.
Have you had a chance to use this new gas sensor? If so, leave a comment and tell us about your experiences.