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Appendix: Calibrate an enteliZONE eZNx CO2 Sensor (eZNT-WI and eZNS)
3. If necessary, enable Manual Calibration mode by setting the AV511
(CO2ManualCalibration) value to 1. In the enteliWEB frontend, select the AV
object and from the command menu select Manual value. Enter the value and
press Save. Put the object back into Auto.
4. When a stable CO2 reading is reached, as viewed from the monitored trend log
(~2 mins), manually set CO2ManualValue AV512 to the known certified
concentration value of the CO2 gas (ppm).
The CO2ManualValue goes to zero to indicate that the calibration value was
accepted. An entry is written to the AV512 C02CalibrationValue description
field (AV512.description) and it includes the manual calibration value and a
timestamp. The previous information in the description field is overwritten.
An internal algorithm in the CO2 sensor uses the single point manual
calibration value to apply compensation across the entire range in a non-linear
manner.
Auto Calibration
Auto calibration looks for periodic minimum CO2 readings for buildings that come
down to the outdoor ambient level during nightly unoccupied periods and calibrate
these minimum values as 400 ppm. This means that the building is unoccupied for
some period each day and that the site elevation allows the CO2 level to drop to 400
ppm daily. The CO2 level decreases by about 3% for every 1000 feet (300m)
increase in elevation above sea level. For example, the ambient CO2 would be
around 370 ppm at 2000 feet (610m).
Note: The manual calibration mode is the default and is generally the preferred
mode.
In auto calibration mode, the sensor assumes the building comes down to 400 ppm
ambient CO2 daily. The internal sensor calibration algorithm requires at least 7 days
(periods at least 18 hours apart) of minimum values within 50 ppm of each other
before calibration is applied. This internal calibration is automatic and continual,
using the last seven minimum values stored, to calibrate the sensor. The thermostat
must be powered continuously during this period. If power is lost, all minimum
values are lost. After a power loss, the unit operates with standard signal
compensation until another set of seven acceptable minimum values are acquired.
Auto calibration does not require a CO2 calibration gas of a known certified
concentration.
Page 102 of 126
eZNT-Wi Programmable Wi-Fi Thermostat Application Guide
Edition 1.4
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