Dear CO2 team,
During the testing of the CO2 sensor I noticed an increased noise figure of the sensor.
Below approximately 620 ppm the noise figure increases. I have no idea why.
All sensors are placed in an temperature controlled chamber.
In the picture you can see 4 lines:
Red = PASCO2 sensor A, interfaced via I2C with our own electronics (interval 5 [s])
Blue = PASCO2 sensor B, interfaced via USB with the evaluation board (interval 10 [s] ?)
Green = SCD41 sensor (Sensirion), interfaced via I2C (interval 5 [s])
Cyan = 415 [ppm] (outside air)
In the bottom graph you can see the difference between successive measurements which we use as a noise figure.
Why is this sensor displaying this behaviour? and how can I resolve this issue?
First, sorry for the wrong forum assignment, but I didn't find the suiting forum.
We are accessing a DSP310 pressure sensor via SPI interface. The sensor's registers can be read, so I obtain expected values reading registers:
0x0D => 0x10 (Product ID)
0x08 => 0xC0 (default MEAS_CFG)
But I cannot write any register, which would be necessary to start a measurement. For a very simple approach, I tried to enable FiFo, (setting register 0x09 to 0x02). But when I read back the register, the value is 0x00 (default). I took care for the cleared high bit during write access. We are using 4-wire SPI.
The SPI-interface was only used by DPS310 in our first HW Setup. We needed another SPI device (MEMS), so we connected it to the same CLK, MOSI and MISO PINS (CS of course on another PIN than DPS310_CS).
For the MEMS, it is possible to read and write registers without any modification of the interface program.
So, the occurring question is, is there a special mechanism to "unlock" DPS310 registers for SPI-write? Is there anything else that could be tested on why the write access fails?
Actual Measurement Result
When CO2 was injected into the closed space with the PAS CO2 Sensor, the CO2 concentration in the GUI increased immediately.
16:10:49(JST)/500ppm ⇒ 16:10:59(JST)/1500ppm
After that, it stabilizes at 32618ppm.
Leave PAS CO2 from enclosed space to open space (≈400ppm) at 16:16:39(JST)
16:31:39(JST)/436ppm, Finally back to the CO2 concentration of the open space. Why does it take so long, 15 minutes, to get back to normal?
Translated with www.DeepL.com/Translator (free version)Show Less
I am using PAS CO2 sensor in single shot mode. Power up sequence: +3.3V , then +12V, then wait minimum 1s.
PWM_DIS connected to 3.3V, PSEL connected to GND.
I trigger a measurement every minute, enabling ABOC in the field BOC_CFG (register MEAS_CFG). [write 0x05 into MEAS_CFG]
Then I wait minimum 2 seconds, and afterwards I read out the measurement value. Outdoor (country side, clean air) I get values around 800ppm. Whether I enable or not the ABOC, the measured values seem to be the same.
Am I missing something?
In the end I assumed there is a sensor offset of ~400ppm, and I subtracted it from the measured values. Is this a valid approach?Show Less
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