User manual CO2 CALIBRATOR
The Rotronic CO2 CALIBRATOR is a portable device used for zero calibration of carbon dioxide sensors. It features a compact, rectangular casing with indicator lights and a connection for tubing. On the front panel, there are several indicator lights (labeled 'Battery charging', 'Change CO2 absorber', 'Pump on', 'Auto shutdown', 'Low battery', 'Low battery, auto shutdown') and a power button. A clear window shows the CO2 absorbent cartridge inside. A white tube is connected to the device, used for gas flow.
General
The 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 too 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.
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 the red LED is flashing evenly. This indicates the CO2 absorbent cartridge has been used for more than 8.5 hours.
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 minutes, the green LED starts to flash with long pulses. This indicates that the unit will shut down automatically within 4 minutes if operated on battery. 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 hardware) |
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 on several factors, but the minimum operational time is 8.5 hours with soda lime from Scarlau. Factors that affect the absorbent power include the 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.
Verification of absorbent by high CO2 concentration
The CO2 concentration of incoming air is 3000 ppm.
Graph titled 'CO2 concentration after passing through Zero Calibration Unit'. The X-axis represents 'Time hours' from 00:00:00 to 21:36:00. The Y-axis represents 'ppm CO2' from 0 to 200. The graph shows a relatively stable low CO2 concentration (around 0-20 ppm) for the initial period, then a sharp increase starting around 12:00:00, reaching 200 ppm by 21:36:00.
For best result, the Zero Calibration Kit should be in operation a while after changing the CO2 absorbent cartridge so that the cartridge will stabilize.
Battery performance
Battery type: Li Ion 2/2S1-LP103450AR/SR, 7.4V, 1550mAh, 11.47Wh. Charging time is about 5.2-6 hours.
Graph titled 'Battery performance'. The left Y-axis represents 'Battery voltage (V)' from 7 to 8.6. The right Y-axis represents 'Charge current (A)' from 0 to 0.07. The X-axis represents 'Time hours' from 00:00:00 to 07:12:00. The graph shows battery voltage starting around 7.2V, increasing to about 8.4V, and then gradually decreasing. The charge current starts at approximately 0.06A and decreases over time as the battery charges.
Typical trickle charge
Graph titled 'Typical trickle charge'. The left Y-axis represents 'Battery voltage (V)' from 0 to 9. The right Y-axis represents 'Charge current (A)' from -0.1 to 0.4. The X-axis represents time in hours, starting from 13:40 and going up to 14:08. The graph shows battery voltage fluctuating around 8.2V to 8.4V during operation, with intermittent charging current pulses that drop to near zero or slightly negative.
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 on 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.
Graph titled 'Cycle life characteristics'. The X-axis represents 'Number of cycles (cycles)' from 0 to 500. The Y-axis represents 'Capacity ratio (%)' from 60 to 100. The graph shows that the capacity ratio remains at 100% up to approximately 100 cycles, then gradually decreases to about 90% at 500 cycles. The charge and discharge parameters are specified as: Charge: CC/CV, 4.2V, 1550mA (1C) × 2.5hrs, 25°C/77°F. Discharge: Constant current 1000mA, 25°C/77°F.
If the Zero Calibration Kit is in standby mode, the battery should be charged at least once a month. Before longer storage, the battery should only be charged to about 75%, with a four-hour charging time.
