The GMD20 is a new CO2 sensor from Vaisala. It uses a CARBOCAP silicon-based microsystem sensor, which guarantees excellent stability and reliability. The sensor requires almost no maintenance, and the recommended calibration interval is five years. The sensor can be equipped with a relay output or a LonWorks interface as an additional option. These features make the GMD20 a very attractive choice for various ventilation and air conditioning applications.
The GMD20/D CO transmitter from Vaisala uses the CARBOCAP® sensor technology and is designed for stable, maintenance‑free operation. The manual covers installation steps, electrical connections, LED status indicators and recommended calibration intervals.
Technical specifications, mechanical data and optional accessories are listed, along with guidance for power supply wiring and troubleshooting. The device operates from a 24 VAC/VDC nominal supply and provides a 0‑20 mA (or 4‑20 mA) analog output.
| Repeatability | < 0.05 %FS/°C |
|---|---|
| Stability | < 5 %FS/5 years |
| Response time | 1 minute (0‑63 %FS) |
| Operating temperature | -5 °C … 445 °C |
| Storage temperature | -20 °C … 470 °C |
| Humidity (short term) | 0 % … 100 % RH |
| Humidity (long term) | 0 % … 85 % RH |
| Flow range | 0 … 10 m/s |
| Analog output | 0‑20 mA or 4‑20 mA and 0‑10 V |
| Power consumption | < 2.5 W (average) |
| Weight | GMD20 140 g, GMD20D 170 g |
| Enclosure rating | IP65 |
| Enclosure material | ABS plastic |
The recommended calibration interval is five years.
It is designed to operate from a nominal 24 VAC or 24 VDC supply.
Average power consumption is less than 2.5 W, with peak currents up to about 170 mA.