https://senseair.com/products/size-counts/s8-residential/

ABC Period: 8 days. The default “tuning speed” is limited to about 30-50ppm/ABC period.

Measurement interval: 4 sec.

Power supply: 4.5 —5.25V unprotected against surges and reverse connection

Power consumption: 300mA peak

4.5 V to 5.25  V DC

PIN

G0Power supply minus terminal
Sensor’s reference (ground) terminal
G+VCC4.5—5.25V
Alarm_OCOpen Collector output for alarm indication
PWM 1 kHzPWM output. Configured as digital output
Used for direct reading by customer’s microcontroller or to provide analog output.		0%, output Low
100%, output High
DVCC_outfrom sensor’s voltage regulator
Output may be usedto logical level converter if master processor runs at 5V

3.3VDC
6mA max
UART_TxDUART data receive line, digital output
UART_RxDUART data receive line, digital input
UART_R/TDirection control line for half duplex RS485 transceiver like MAX485
bCAL_in/ CALbackground calibration, which requires that the sensor is exposed to fresh air 400ppm CO2 (4-8 sec)
CAL (zero calibration), cell to be completely evacuated from CO2 (>16 sec), closed to G0