Appendix: Calibrate an enteliZONE eZNx CO2 Sensor (eZNT-WI and eZNS)
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eZNT-Wi Programmable Wi-Fi Thermostat Application Guide
Edition 1.4
The CO2 sensor SC backplate contains a port on the bottom that supports inserting
a tube which directs a low flow (0.3 – 0.5 l/min) of known CO2 concentration gas
across the CO2 module.
a. Obtain CO2 in a known concentration, e.g. a nominal 1000 ppm with regulator
allowing varying the flow of CO2 gas. The certified CO2 concentration value
(e.g. 940 ppm ) is typically displayed on a label attached to the gas cylinder.
b. Obtain a 5mm (3/16”) outside diameter plastic hose of at least 5cm (2”)
length that can be used in the eZNT-Wi calibration port.
c. Connect this plastic hose to the CO2 cylinder via additional hose and reducers
as necessary to achieve a length that will reach between the mounted eZNT-
Wi and the CO2 cylinder location.
d. Insert the 5mm OD plastic end piece into the port on the left bottom side of the
backplate. If necessary, tape can be wrapped around the 5 mm hose to ensure
a snug fit. The hose should be gently inserted until resistance is felt.
e. When needed, use the gas regulator to send a low flow rate of around 0.3 liters
per second into the channel that connects to the plastic enclosure around the
CO2 sensor. Excessive flow can introduce temperature instability due to
cooling from expansion of the gas and can adversely affect reading.
There are two methods to use for a manual field calibration of a CO2 sensor:
Method I: Manual single point calibration using on-screen menu
1. Log into the on-screen Config menu. See the A: Configuration Menu Access
content in the
Configuration Using the On-Screen Menu
section.
