User Manual

Page 12 ams Datasheet
Document Feedback [v1-06] 2019-Feb-07
CCS811 − Detailed Description
Early-Life (Burn-In)
CCS811 performance in terms of resistance levels and
sensitivities will change during early life. The change in
resistance is greatest over the first 48 hours of operation.
CCS811 controls the burn-in period allowing eCO
2
and eTVOC
readings to be used from first power-on after 60 minutes of
operation in modes 1-3.
Conditioning Period (Run-In)
After early-life (Burn-In) the conditioning or run-in period is the
time required to achieve good sensor stability before
measuring VOCs after long idle period.
After writing to MEAS_MODE to configure the sensor in mode
1-4, run CCS811 for 20 minutes, before accurate readings are
generated.
The conditioning period must also be observed before writing
to the BASELINE register.
eCO
2
The equivalent CO
2
(eCO
2
) output range for CCS811 is from
400ppm up to 29206ppm.
eTVOC
The equivalent Total Volatile Organic Compound (eTVOC)
output range for CCS811 is from 0ppb up to 32768ppb.
Temperature and Humidity Compensation
If an external sensor is available this information can be written
to CCS811 so that they will be used to compensate gas readings
due to temperature and humidity changes. When ENV_DATA
has been written, the next eCO
2
and eTVOC readings (in
ALG_RESULT_DATA) may not yet use the latest ENV_DATA. All
subsequent reading will use the ALG_RESULT_DATA. Refer to the
ENV_DATA (Environment Data) Register (0x05).
Interrupt and Interrupt on Threshold
At the end of each measurement cycle (250ms, 1s, 10s, 60s) a
flag is set and optionally interrupt (nINT) pin asserted. Refer to
the MEAS_MODE (Measurement and Conditions) Register
(0x01). The user can choose to only assert nINT if the eCO
2
value
changes into a different range set by register values. Refer to the
THRESHOLDS Register (0x10).