Presentation on microglow technology given by Mikko Aronniemi at SEMICON Europa 2013.

1. Optical CO2 module with chip‐on‐board MEMS
components and injection‐molded plastic optics
2013‐10‐07
Mikko Aronniemi
Vaisala

2. Vaisala
• Global leader in environmental and
industrial measurement
• Instruments for measuring humidity, temperature,
dewpoint, carbon dioxide, pressure, weather
• Serves customers in weather and controlled environment
markets
• The Vaisala Group
– Employs over 1400 professionals
– Has 30 offices worldwide
– Net sales of 293.3 million euros (2012)
– Main markets EMEA (37%), Americas (37%), APAC (26%)
– Products used in over 150 countries
– A‐series shares quoted in NASDAQ OMX Helsinki stock exchange

3. CO2 measurement for HVAC
• Indoor air is contaminated by the CO2 people breathe
out and by other chemical compounds
– Too low ventilation means bad air quality and an
unpleasant environment
– Too effective ventilation increases energy
consumption
 Demand‐controlled ventilation based on CO2
measurement
– Particularly important for buildings with varying occupancy
24/7
CO2 concentrations
• Outdoor air: ~400 ppm
• Exhaled air: 20 000 – 50 000 ppm
• Good indoor air quality: <1000 ppm
Ref. http://www1.eere.energy.gov/femp/pdfs/fta_co2.pdf

4. Optical CO2 measurement technology
•
•
•
CO2 molecules absorb IR radiation at a characteristic wavelength (4.26 µm).
Attenuation of IR intensity gives CO2 concentration.
For a stable measurement, a reference is needed to compensate other effects
on intensity: changes in IR source emission, optics reflection etc.
CO2
One IR source, one filter + detector
Reference: Assumed background concentration
Two IR sources, one filter + detector
Reference: Added IR source
One IR source, two filters + detectors
Reference: Added filter + detector
Vaisala CARBOCAP® sensor
One IR source, one tunable filter + detector
Reference: Measurement at non‐absorbing
wavelength

5. CO2 sensor design
New
Current
6 cm
10 cm
Design objectives for the new sensor
• Manufacturing cost to half
• Power consumption to half
• Better performance
• Increased lifetime
Solutions
• Automated manufacturing, no manual
soldering
• MEMS IR source, no lamp
• Sensor chips directly mounted on PCB
• One‐piece plastic optics

6. New Vaisala CO2 module
• Single‐beam, dual‐wavelength NDIR measurement
• Standard measurement range 0 ... 5000 ppmCO2
• Accuracy 30 ppmCO2 + 2% of the reading
• Stability according to CEC‐400‐2008‐001‐CMF standard
• Operating environment
– temperature ‐5 ... +55 C
– humidity 0 ... 95 %RH, non‐condensing
• Power consumption 0.2 W average
• Lifetime >15 years
• I2C digital output
• Output interval 2 s
• Traceable calibration certificate at 1000 and 2000 ppmCO2

7. Manufacturing
1) Sensor chip manufacturing
3) Pick‐and‐place chip mounting
5) Assembly ready
2) Electronics manufacturing
4) Cuvette mounting
6) Testing and calibration

8. Optics
•
•
Filter and detector
IR source
Optical path length 110 mm
Collection efficiency 5 %

9. IR source – Vaisala microglow
Emitter
3 mm
Membrane
for thermal
insulation
Frame
CO2 abs.
Ref.

10. IR source – temperature distribution
880 C
LI02
LI01
< 80 C
640 CC
638.9
Zoom to emitter area
LI02
600
550
500
480 C
LI01

11. IR source – lifetime and stability

12. Tunable filter – Vaisala FPI chip
Fabry‐Pérot interferometer
CO2 abs.
Air gap
Upper mirror
Lower mirror
CO2
0 ppm
CO2
5000 ppm
FPI
Si substrate
Detector
Example of the pass band
CO2 abs.
Ref.
Ref.

13. Detector – Vaisala thermopile chip
Absorbator
3 mm
CO2 abs.
Ref.
Thermocouple

14. Test results – long‐term stability
Typical environment (N = 23)
1000 ppmCO2
Harsh environment (60 C, 90 %RH, N = 60)
1000 ppmCO2
CEC‐400‐2008‐001‐CMF
2000 ppmCO2
2000 ppmCO2

15. Test results – T and P dependency
Effect of temperature and pressure is compensated with a product‐specific model.
Temperature dependency (N = 29)
Pressure dependency (N = 20)
500 ppmCO2
500 ppmCO2
5000 ppmCO2
5000 ppmCO2