Closed michapr closed 5 years ago
Hi Michael
The start measurement command will start the fan and put the sensor in to measure mode. You only have to trigger that once.
The stop command will stop the fan and disable measure mode (put sensor to sleep). Only use this command when your done measuring. Don't do this between consecutive read-outs.
We recommended to don't turn of the sensor for as long as your measurement takes. E.g several days, weeks, month. After the start-up the sensor requires a couple of minutes to achieve a stable flow and show the most accurate values.
The recommended sequence is (as pseudo code):
startup();
start_measurement();
sleep(60s); // e.g. first minute is not accurate enough for our use case.
while (1) {
while (not data_ready) {
sleep(100ms);
}
read_measurement();
sleep(5s);
}
stop_measurement();
shutdown();
Maybe it also helps to clarify that the SPS30 is not the typical "dumb" i2c device where you set the pointer. The SPS (actually all Sensirion Sensors) execute commands and maintain an internal state machine. The SPS goes even further in that it keeps states between power cycles. So when your device looses power while measuring, it will start measuring again automatically when it's powered the next time. stop_measurement()
thus also ensures that the SPS will not start measuring again automatically after a power cycle.
Thank you for clarify this. Maybe it could be helpful to add some of these information to the documentation?
I get these values (for inside room) - are these possible right? PM1.0 .. PM10 1.50 / 1.55 / 1.55 / 1.55 [μg/m³] PM0.5 .. PM10 10.65 / 12.22 / 12.26 / 12.26 / 12.26 [#/cm³] Typical Particle Size 0.53 [μm]
(maybe you could give some reference values anywhere for users? So that they can be sure that received values correct ;) ...)
Thanks! Michael
[edit:] have now values for PM1.0 ..PM10 between 0.40.. 0.43 μg/m³ in my room - can this be a real value?
ok,... after have "optimized" my experimental setup get stable values.
Values seems for me very low (μg/m³) - or what do you think? Have also checked with original sample code - get the same values here. And - no big changes within 18 hours.
Values seems for me very low (μg/m³) - or what do you think?
You could try to tear apart a piece of paper very close to the sensor, this should give you a spike of particles for a short time. Another thing you can try is to light a candle which will also produce particles.
I have of course tried this before (candle) and have seen that values will be changed. But 2 - 3 μg/m³ for a living room (home office) looks for me too low, that's why was asking about the value ranges. Want to be sure that I can "trust" the values I have got ;)
@michapr It really depends on your environment. 2 - 3 μg/m³ for a living room is actually reasonable. Depending on the area you live in the values should increase if you open a window. It is quite usual that there are not a lot of particles indoors. E.g. in our office or at my home I get similar values.
I am not sure what kind of reference values you are expecting. E.g. there is no world wide standard for Air Quality based on PM values. You can find some interpretations on Wikipedia: https://en.wikipedia.org/wiki/Air_quality_index
You can find the technical specifications on the datasheet: https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/0_Datasheets/Particulate_Matter/Sensirion_PM_Sensors_SPS30_Datasheet.pdf
Thanks, of course I know these and other documents. closed.
What's the best place for feedback on the data sheet? For the Version 1.0 – D1 – March 2020
version
I've noted (all for i2c on a V2.2 firmware sensor)
Hi @kevinjwalters,
Thanks for reaching out. For feedback on data sheets, please reach out to our technical support team via the "Contact" link on https://sensirion.com/support.
Regarding your question #4, the 5ms delay: Please note that the data sheet is authoritative, and the sample code may use different timings for a number of reasons (typically to increase cross-platform compatibility); therefore it should only be reported as an issue in the data sheet if tests show that it actually fails without the delay.
Hi, not full clear from documentation for me - maybe you could explain? What is the right sequence for reading data?
and for next loop again 1/2/3/4 ?
If I will skip the second step (stop measurement) will get other values. I know that I must not check flag (step 3) if loop > 1 second (currently use about 5 seconds). When the "Stop" should be used?
Thanks! Michael