When Paying Extra Does Not Get You Extra Accuracy
Usually, a better product value ought to correlate with higher high quality, options and/or efficiency. Take for instance pc CPUs: The upper the price of the CPU, the higher the efficiency. The graph beneath chart illustrates that very nicely:
CPU Efficiency vs Worth. Supply: cpubenchmark.internet
So let’s have a look at air high quality displays.
In relation to air high quality displays, we have to first resolve what’s crucial efficiency criterion? Is it the design? Is it the scale? Is it the connectivity?
These would possibly all be vital elements however the important thing efficiency criterion is the accuracy of the monitor. If a monitor doesn’t ship correct measurements, even the very best design is of no use. So let’s take a look on the correlation between air high quality monitor costs and accuracy. For this evaluation, we solely have a look at the accuracy of PM2.5 as this is among the most typical air high quality parameters and, thus, one that almost all displays measure.
South Coast AQMD, does unbiased checks of air high quality displays and many of the well-known displays went by way of this testing. So this is a superb information supply that we will use for our evaluation. I downloaded the information as of April 12, 2023 and regarded on the correlation between value and accuracy. As an indicator for the accuracy, the settlement between the sensors and a typical reference instrument was decided. To quantify this settlement, South Coast AQMD decided the R2 worth which measures the linear relationship between the sensor and their reference instrument. An R2 approaching the worth of 1 displays a close to good correlation, whereas a price of 0 signifies an entire lack of correlation.
Once we plot the accuracy (R2) towards the value of all of the displays examined, we will see the next:
R2 vs Worth. Knowledge Supply: South Coast AQMD Knowledge
It seems to be fairly completely different from the charts about CPU efficiency, doesn’t it? The worth doesn’t appear to have an effect on the accuracy of the monitor which can be seen by the flat development line.
That is clearly not what we anticipated, so let’s drill a bit extra into the information.
Within the subsequent determine, I separated the displays into completely different value ranges and present the typical, minimal, most in addition to 25% and 75% quartile of R2. Right here we will see that displays within the value vary of USD 100 – 200 appear to supply the very best accuracy and that the most costly displays accuracy is just about the identical as of the most cost effective displays.
R2 vs Worth Ranges. Knowledge Supply: South Coast AQMD Knowledge
So, a monitor that prices USD 2000 delivers the identical accuracy as a monitor for USD 200 (for PM2.5 measurements).
Since we solely give attention to the accuracy of PM2.5 and put the entire value of the monitor in relation, we might miss some vital features like:
- Dearer displays sometimes measure extra air pollution, e.g. NO, NO2, O3 and so on. And a few of these sensors are fairly pricey.
- Dearer displays might need higher connectivity choices, e.g. 4G, LoRa and so on.
- Dearer displays might need extra strong enclosures and higher mounting choices
Above might partially clarify the explanation for the upper value, nevertheless we must always at the least count on the identical or higher accuracy for PM2.5 which is paradoxically not the case.
What’s your expertise with the accuracy of air high quality displays? We’re cusious, drop us a line!
By the best way, we’re at present doing co-location testing of our new open-hardware outside monitor Open Air and first checks point out an R2 of 0.8 – 0.9. We’ll publish detailed take a look at leads to the approaching weeks.