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2. Apply fresh air (400ppm) at device inlet
3. Monitor sensor measurement at Input Register address 1 and wait until reading stabilized (~2
minutes)
4. Set ZERO_CO2 Coil (address 2) to request zero action (write 1 or TRUE value to register)
5. Set CONF Coil (address 7) to confirm. After confirmation, the device will perform zero action assuming
the provided gas is 400ppm. Coils will automatically be reset. A new zero value will also be updated on
Holding Registers address 6
6. Read sensor measurement at Input Register address 1 to verify if sensor is zero-ed correctly. This
value should be 4 (400ppm or 0.04%).
7. Put device back to default Trigger measurement mode (write 300 to TRIGGER_INTERVAL Register)
Perform a zero calibration using a known concentration of CO2 (other than 400ppm)
1. Put device in Continuous measurement mode (write 0 to TRIGGER_INTERVAL register address 20)
2. Apply known concentration at device inlet (for instance 1000ppm)
3. Monitor sensor measurement at Input Register address 1 and wait until reading stabilized (~2
minutes)
4. Set ZERO_CO2 Coil (address 2) to request zero action (write 1 or TRUE value to register)
5. Set Holding Register address 16 to the known concentration, for instance 10 (1000ppm or 0.1%)
6. Set CONF Coil Register (address 7) to confirm. After confirmation, the device will perform zero action
using the known concentration at Holding Register address 16. Coils will automatically be reset. A new
zero value will also be updated on Holding Registers 6.
7. Read sensor measurement at Input Register address 1 to verify if sensor is calibrated correctly. This
value should be the same as the one written to Holding Register 16.
8. Put device back to default Trigger measurement mode (write 300 to TRIGGER_INTERVAL Register)
CO2 Span Calibration
Calibrating span on the CO2 sensor can be performed in either Trigger or Continuous measurement mode.
To perform a span calibration for CO2 sensor:
1. Apply Calibration gas at device inlet
2. Monitor sensor measurement at Input Register address 1 and wait until readings stabilized (typically 2 to
3 measurement updates in Trigger mode or >=2 minutes in Continuous mode)
3. Read sensor’s SPAN value at Holding Registers (address 5)
4. Calculate Span value using the provided formula and round this value to the nearest integer
For example: Calibrating sensor with 15% CO2 standard gas, current sensor measurement is 1400 (14%)
and current span value is 8000. New span value = 1500*8000/1400 = 8571
5. Write new span value back to the sensor’s Holding Register (address 5)
6. Read sensor measurement at Input Register address 1 to verify if sensor is calibrated correctly.
O2 Sensor Calibration
Calibrating span on the O2 sensor can be performed in either Trigger or Continuous measurement mode. You can
use certified standards with known concentration of O2 or fresh ambient air (20.9% O2).
A zero calibration is not necessary, however you can use Holding Register address 4 (O2_ZERO) to fine-tune the
measurement baseline.
Perform a zero calibration using fresh ambient air (20.9% O2)