
User manual 
CO2 CALIBRATOR 
General 
CO2 CALIBRATOR is used to zero calibrate carbon dioxide sensors. The unit produces 
carbon dioxide free air from the ambient air. 
The main process is that soda lime is used to absorb the carbon dioxide in the air. Carbon 
dioxide reacts chemically with the calcium hydroxide and sodium hydroxide in soda lime to 
form calcium carbonate and sodium carbonate. The air that has passed through soda lime 
contains much less carbon dioxide. 
If the soda lime has a violet colour it has lost much of its absorbing capability and can no 
longer be used to produce carbon dioxide free air. Several tests show that this colour 
indicator cannot be trusted. The colour indication disappears after a short time so the 
absorption power of the cartridge can easily be overvalued. If a sensor is zero calibrated with 
air containing to much carbon dioxide the readings of the sensor will be too low. Tests have 
shown that a cartridge with 5 ml of soda lime has an average absorption time of about 9 
hours.
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Function parameters 
Battery charging 
The red LED is lit with a fixed light when the battery is charged (no indications of any alarm) 
Change CO2 absorber 
The CO2 absorbent cartridge needs to be replaced when red LED is flashing evenly. (The 
CO
 absorbent cartridge has been used more than 8.5 hours) 
2
Pump on 
The green LED is lit with a fixed light when the pump is working (no indications of any alarm) 
Prealarm 
The unit is operating and after 21 min the green LED starts to flash with long pulses. This 
indicates that the unit will shut down automatically within 4 min if operated on battery. 
The unit will continue to operate if the charger is used. The green LED will flash with long 
pulses but the unit will continue to operate. 
Low battery 
The unit is operating and the green LED starts to flash with short pulses. This indicates that 
the battery voltage is below 7,1V. 
Technical data 
Weight    258 grams included absorbent cartridge (8 grams) 
Length    156mm 
Width    89mm 
Thickness   26mm 
Gas flow out  320-340ml/min 
(Gas flow can be changed between 50ml-350ml/min by hard ware) 
Volume of CO2 absorbent cartridge 
The volume with maximum filling = 7ml (marked size 5ml length=72.2 mm outer diameter 
=13.7 mm) 
The absorbent power of the absorbent cartridge is dependent of several factors, but the 
minimum operational time is 8.5 hours with soda lime from Scarlau.  
(Factors that affect the absorbent power is type of chemicals, packing density of chemicals 
the tilt of the unit and the suction/pressure of the pump)  
The average flow of the pump through an OBA8 sensor is 320ml/min 
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CO2 concent r a t i on a f t er pa ssing t hr ough Zer o Cal i br a t i on Uni t
0
20
40
60
80
100
120
140
160
180
200
00:00:00 02:24:00 04:48:00 07:12:00 09:36:00 12:00:00 14:24:00 16:48:00 19:12:00 21:36:00
Battery perf or mance
7
7,2
7,4
7,6
7,8
8
8,2
8,4
8,6
00:00:00 01:12:00 02:24:00 03:36:00 04:48:00 06:00:00 07:12:00
0
0,01
0,02
0,03
0,04
0,05
0,06
0,07
Bat t ery voltage (V) 
Charge current (A )
Verification of absorbent by high CO2 concentration 
The CO
concentration of incoming air is 3000 ppm. 
2 
For best result the Zero Calibration Kit should be in operation a while after changing the CO
2 
absorbent cartridge so that the cartridge will stabilise. 
Battery performance 
Battery type Li Ion 2/2S1-LP103450AR/SR 7,4V 1550mAh. 11,47Wh  
Charging time is about 5.2-6 hours. 
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0
1
2
3
4
5
6
7
8
9
13:40
14:32
15:25
16:17
17:10
18:02
18:55
19:47
20:39
21:32
22:24
23:17
00:09
01:02
01:54
02:46
03:39
04:31
05:24
06:16
07:09
08:01
08:53
09:46
10:38
11:31
12:23
13:16
14:08
-0,1
-0,05
0
0,05
0,1
0,15
0,2
0,25
0,3
0,35
0,4
Battery vol tage (V)
Charge current (A)
The battery is charged during operation 
Operation time of the battery 
Operation time by normal operation is 15 hours before the low battery alarm is activated. The 
battery will shut down automatically when the battery voltage is below 5,0V. 
Service life of the battery 
The service life of the battery is dependent of its discharging and charging cycles. The 
service life of the battery should be 1000 cycles before the capacity is below 85% if the 
charging current is 400mA and the discharging current is 80mA. 
The battery will last about four years with three cycles of discharges and recharges a week. 
(High storage temperatures or frequent cycles of discharges and charges may shorten the 
battery life) 
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If the Zero Calibration Kit is in standby mode the battery should be charged at least once in a 
month. Before longer storage the battery should only be charged to about 75 %, four hours 
charging time. 
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