Appendix: Calibrate An Entelizone Eznx Co2 Sensor (Eznt-Wi And Ezns); Manual Calibration - Delta enteliZONE eZNT-Wi Series Application Manual

Appendix: Calibrate an enteliZONE eZNx CO2 Sensor (eZNT-WI and eZNS)
Appendix: Calibrate an enteliZONE eZNx CO2
Sensor (eZNT-WI and eZNS)
This topic currently applies to CO2 models for eZNT-Wi and also a planned
eZNS CO2 model with a hardware revision greater than 3.2. The current
hardware revision is 3.1. The newer eZNS network sensor uses the same
back plate as the eZNT-Wi product.
The eZNT-Wi controller includes a new CO2 sensor that is flat mounted on the circuit
board. This approach allows the CO2 models to be flush mounted in the same
manner as the non-CO2 models. The eZNT-Wi SC backplate no longer has a CO2
sensor housing that protrudes from the back plate into the wiring box space. The
CO2 sensor NDIR dual channel design compensates for long term drift and supports
both a manual calibration mode and an auto calibration mode.
The CO2 sensor relies on the precise positioning of light beams and is sensitive to
shocks during shipping and also mishandling of an eZNTx thermostat. This sensor
supports two methods to compensate for these offsets as well as drift over time.
Both manual and auto calibration apply a single point calibration directly to the
internal CO2 sensor from a known CO2 level and apply the compensation non-
linearly across the entire CO2 range.
The calibration is not a constant offset across the range; the CO2 AI
Calibration object value should NOT be used to calibrate the sensor.

Manual Calibration

A single point manual calibration mode is available for buildings that have irregular
occupied periods or do not come down to 400 ppm ambient CO2 overnight. Manual
calibration is the preferred calibration method, as it does not depend on building
operating conditions. Manual calibration is a single compensation applied to the CO2
module (not the AI calibration property) using a known gas concentration or
calibrated CO2 sensor.
Manual calibration uses a known measured value from a calibrated reference sensor
or flowing CO2 gas at a known concentration across the CO2 sensor. This known
concentration is the raw value that the controller writes down to the CO2 module.
The following procedure describes using a CO2 gas, however an accurate calibrated
reference could be used to determine the calibrated value to enter.
Page 98 of 126 eZNT-Wi Programmable Wi-Fi Thermostat Application Guide
Edition 1.4