Vaisala GMM220 CO2 transmitter modules are versatile instruments for measuring CO2 in industrial applications. The CARBOCAP® sensor is silicon based and its operation is based on the NDIR Single-Beam Dual-Wavelength principle. The modules can be configured for different CO2 measurement ranges and analog output ranges.
The GMM220 series are CO₂ transmitter modules that use a silicon‑based CARBOCAP® NDIR sensor. They are available with two probe types (GMP221 for higher concentrations and GMP222 for lower concentrations) and support analog voltage/current outputs as well as a serial interface for data acquisition.
The guide covers mechanical mounting, electrical connections, LED status indicators, serial command protocol, pressure and temperature compensation settings, technical specifications, compliance information, warranty, accessories and support procedures.
| CO₂ measuring range (GMM221) | 0–10,000 ppm |
|---|---|
| CO₂ measuring range (GMM222) | 0–20 % vol |
| Accuracy | ±1.5 % of range + 2 % of reading |
| Power supply | 11–20 VDC or 18–30 VDC |
| Humidity range | 0–100 % RH (non‑condensing) |
| Analog output resolution | 12 bits |
| Average current consumption | 100 mA |
Set the serial port to 9600 baud, 8 data bits, 1 stop bit, no parity and no flow control.
Use the DISP command with option 2 for ppm or option 4 for percent; for continuous output use MF_MODE with the same options.
During normal operation the green LED blinks while the red LED remains off.