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Measurement
 
 
Ventilation Rate
 
Q: What is Ventilation Rate?
A: It represents how much air is introduced into the indoor space from the outside. Low values indicate low
  ventilation rate and potentially poor air quality. High levels indicate excessive ventilation and potential.
Excessive energy usage.
Q:

How does CO2 Monitor measure Ventilation Rate?

A: If one person in a room exhales out 18.5cc CO2 per breath and frequency is16/ min, then one person in a
  room exhales out 300cc CO2 per minute.
- CO2 outside is usually 400ppm → X; CO2 in the room → Y
  - The CO2 monitor can calculate the Vent Rate as 300/(Y-X)
Q: What is L/s/p or lps?
A: It's "liter per second per person".
Q: What is Cfm/p?
A: It's "cubic feet per minute per person".
Calibration
 
Q: Preparation: before calibrating , you need standard gas or semi-standard gas.  There are 3 methods
  to get standard gas.
A:
Method A: use CO2 in office/building
  - Use two monitors (One is for calibration, one is calibrated (new).
  - Use ambient room gas for calibration in office, wait at least 10 min, until the CO2 reading doesn't
    change. (notice: user must not breathe toward the device, CO2 from the user will affect the reading)
  - Use the reading of the new device as the standard.
  - Calibrate the device using the process below.
Method B: use CO2 outsides
  - Use ambient room gas for calibration outsides, wait at least 10min, until the CO2 reading doesn’t
    change. (notice: user must not breathe toward the device, CO2 from the user will affect the reading)
  - Use 380~420ppm as the standard reading.
  - Calibrate the device using the process below.
Method C: use standard CO2 in the bottle
  - Pump the standard CO2 gas (0~1000ppm, flux = 0.1~0.2 liter/min) into the ZG monitor from the Gas
    Entry Hole, wait about 2~3 min.
  - Calibrate the device using the process below
 
Calibration process – can be found in the User Manual
  The CO2 monitor has been calibrated in the factory and is suggested to recalibrate every 12 months for
  professional applications.  Please follow below steps.
 
  • If battery icon shows low power, please replace new batteries or use AC adapter.
  • Press the Mode button(5), until CALI flashes.
  • Press Enter(2), CALI shows on display.
  • Adjust the lower display to ambient CO2 value by Up/Down (4/3) Button.
  • Press Mode button (5) more than 10 sec., CALIBRATING flashes.
  • Calibration will be done after 5 min and LCD will appear "PASS". If LCD appear "FAIL",   
    please calibrate once again.
  • Press Enter(2), return to UserMode.
If user thinks the calibration result is not fine, he can use RcFS (Recover Factory Setting) to recover the
previous accuracy.
ABC (Automatic Background Calibration)
 
Q: Do you have ABC for the CO2 monitors?
A: We use dual channel (beam) NDIR, thermopile from PerkinElmer, the sensor drift is less than 15ppm/
  year, so  ABC is not necessary for our CO2 monitor.
Q: What is ABC?
A: The CO2 level drops to the outside level during unoccupied periods which eliminates the need of manual
  calibration; but this will not work properly for applications in spaces without long unoccupied periods.
Q: How to ensure the CO2 long-term stability if without ABC?
A:
Many sensors experience long-term drift which may be resulted from various causes including gradual
  chemical changes, exposure to water vapor, smoke, dust; and variations in the electrical power supply
  like battery degradation, etc.
The problem of uncompensated drift is especially serious in NDIR sensors.  For  carbon dioxide
  sensors that are used in fire detectors and in ventilation monitors the difficulty is much higher because
  these devices are expected to operate for   ong periods of time, even for years, without attention. These
  applications require long-term stability to avoid of excessive false alarm rates and erratic ventilation.
The classic approach to solve this problem is to provide within the sensor a reference channel that
  specifically measures the degradation caused by  above mentioned factors. This increases the cost
  and complexity of the sensor.  We use dual-channel design, the sensor drift is <15ppm/year, which
  helps to compensate the drift to maintain the long-term stability.