Casella CEL Indoor air quality monitor - Manual (Page 33)

12.5 CO
2
Monitor
This monitor provides a robust and accurate
method for obtaining CO
2 measurement in site
survey applications.
The sensor is based on an “Infra-red Absorption”
technique. The unit incorporates a single beam
emitter, where the single beam is split into two
using solid state circuitry. This provides a dual
wavelength infra-red sensing chamber with no
moving parts, which results in a low drift, high
accuracy monitor with fast response and low
power consumption.
The unit incorporates a diaphragm pump to draw
the sample air into the measurement chamber,
thus reducing the response time as compared to a
diffusion type of unit. A display on the front of the
instrument provides the user with real time
readings of the CO
2 concentration.
Sensor Specifications
Specification
Operating Range Standard = 0 to 3000 ppm (0.3%)
Options: 1%, 3%, 10%, 30%, 100%
Power Required 24 V DC (range 18 to 30 V DC) at 6 W
(250 mA)
Response Time (T
90
) 10 S
Operating Temperature 0
o
C to 45
o
C
Warm Up Time On initial power up, 30 S
Humidity Effects Unaffected by humidity (non-condensing)
Sensor Protection Internal particle filter
Operation An integral pump is fitted that draws air
through the sensing head
Air Flow Control The pump is flow controlled to ±5% of a
nominal 0.5 l/min (with max. back
pressure of 10 cm H
2
O
Accuracy ±2% of full scale (calibration gas
accuracy not included)
Stability ±2% of full scale over 12 months
Hysteresis Zero ±0.3% - Span ±1.5%
Zero Drift at Constant Temp. ±2% full scale per 12 months
Zero Drift at Ambient Temp.
±0.03% full scale per
o
C
Accuracy over calibrated
period as a % of full scale 60 ppm (cal. per year)
30 ppm (cal. 6 monthly)
15 ppm (cal. 3 monthly)
Page 33 of 42
MICROTHERM indoor air quality &
WinIaq Application Software - User Manual