Vaisala GMP251 CO₂ Probe


  • Measurement range 0 … 20 % CO2
  • Intelligent, standalone probe with analog and digital outputs
  • Compatible with Indigo transmitters and Insight PC software
  • Wide operating temperature range (−40 … +60 °C)
  • IP65-classified housing
  • Integrated temperature measurement for CO2 compensation purposes
  • Compensations also for pressure, oxygen, and humidity
  • Sensor head heated to prevent condensation
  • Compatible with Indigo transmitters, RFL100 data logger, and Insight PC software

Dpstar is a leading supplier of environmental measurement sensors for temperature, relative humidity, pressure, dew point, CO2, and other environmental condition monitoring for industrial process application and research. Since the ’90s, we earned a reputation as a trusted partner to our clients through our commitment and dedication. We are an authorized distributor and supplier of measuring sensors solutions from renowned manufacturers Vaisala. Vaisala is a global leader in environmental and industrial measurement. Building on 80 years of experience, Vaisala provides observations for a better world. Vaisala is a reliable partner for customers around the world, offering a comprehensive range of innovative observation and measurement products and services.

The Vaisala CARBOCAP Carbon Dioxide Probe GMP251 is an intelligent, stand-alone, %-level probe for measuring CO2 in life science incubators, cold storage facilities, fruit and vegetable transportation, and in all demanding applications where stable and accurate percentage level CO2 measurements are needed. The operating temperature range is -40 … +60 °C and the measurement range is 0 … 20%CO2. The GMP251 is based on Vaisala’s unique, second-generation CARBOCAP technology that enables exceptional stability. A new type of infrared (IR) light source is used instead of the traditional incandescent light bulb, which extends the lifetime of the GMP251. It has full temperature and pressure compensations of CO2 measurement – integrated temperature measurement for compensation purposes. The sensor head is heated to prevent condensation. Digital output over RS-485: Modbus & Vaisala Industrial Protocol. A calibration certificate is always included with the product The GMP251 probe is part of the Indigo product family and can also be connected to the Indigo500 and Indigo200 series transmitters to extend its features, for example, for a display or relays. The GMP251 can also be used with the free Insight PC Software.


Key Benefits

Easy To Use Social Clean

The GMP251 is a all-in-one probe, which makes it easy and fast to install. The probe is resistant to dust and most chemicals, such as, H2O2 and alcohol-based cleaning agents. The probe’s surface is smooth, which makes it easy to clean.

Reliable & accurate

With the wide operating temperature range, the GMP251 is suitable for a large number of applications. The probe provides accurate and stable measurements also in varying conditions.


Measurement Performance
Measurement range 0 … 20 %CO2
Accuracy 1)
At 5 %CO2 ±0.1 %CO2
At 0 … 8 %CO ±0.2 %CO2
At 8 … 20 %CO2 ±0.4 %CO2
Calibration Uncertainty
At 5 %CO2 ±0.07 %CO2
At 20 %CO2 ±0.27 %CO2
Long-Term Stability
At 0 … 8 %CO2 ±0.3 %CO2/year
At 8 … 12 %CO2 ±0.5 %CO2/year
at 12 … 20 %CO2 ±1.0 %CO2/year
Temperature Dependence
With compensation at 5 %CO2, 0 … +50 °C (+32 … +122 °F) < ±0.05 %CO2
With compensation, 0 … 20 %CO2,−40 … +60 °C (−40 … +140 °F) ±0.045 % of reading/°C
without temperature compensation at 5 %CO2 (typical) -0.25 % of reading/°C
Pressure Dependence
With compensation at 5 %CO2
700 … 1100 hPa
±0.05 %CO2
With compensation, 0 … 20 %CO2
500 … 1200 hPa
±0.015 % of reading/hPa
Without compensation (typical) +0.15 % of reading/hPa
Humidity Dependence
With compensation, 0 … 20 %CO2,
0 … 100 %RH
±0.7 % of reading (at +25 °C (+77 °F))
Without compensation (typical) +0.05 % of reading / %RH
O2 Dependence
With compensation, 0 … 20 %CO2,
0 … 90 %O2
±0.6 % of reading (at +25 °C (+77 °F))
Without compensation (typical) -0.08 % of reading / %O2
Start-up, warm-up, and response time
Start-up time at +25 °C (+77 °F) < 10 s
Warm-up time for full spec. < 4 min
Response time (T90):
With standard filter < 1 min
Flow-through option with > 0.1 l/min < 1 min
With spray shield < 2 min
Flow rate dependence (for flow-through option)
Flow rate dependence:
< 1 l/min flow No Effect
1 … 10 l/min flow < 0.6 % of reading/ l/min
1) At 25 °C (77 °F) and 1013 hPa (incl. repeatability and non-linearity).
EU directives EMC, RoHS
EMC compatibility EN 61326 1, basic electromagnetic environment
Compliance marks CE, RCM
Operating Environment
Operating temperature of CO2 measurement −40 … +60 °C (−40 … +140 °F) 1)
Storage temperature −40 … +70 °C (−40 … +158 °F)
Humidity 0 … 100 %RH, non-condensing
Condensation prevention Sensor head heating, when power on
IP rating, probe body IP65
Chemical tolerance (temporary
exposure during cleaning)
• H2O2 (2000 ppm, noncondensing)
• Alcohol-based cleaning agents (for example ethanol and IPA)
• Acetone
• Acetic acid
Compensated 500 … 1100 hPa
Operating < 1.5 bar
Gas flow (for flow-through option)
Operating range < 10 l/min
Recommended range 0.1 … 0.8 l/min
1) Occasional short-term exposure to up to +90 °C (+194 °F) allowed, provided that the probe is fully installed inside the measured condition and power is switched on. Accuracy specification not applicable if used in temperatures above +60 °C (+140 °F).
Mechanical Specifications
Weight, probe 45 g (1.59 oz)
Connector type M12 5-pin male
Probe housing PBT polymer
Filter PTFE membrane, PBT polymer grid
Connector Nickel plated brass
Probe diameter 25 mm (0.98 in)
Probe length 96 mm (3.78 in)
Inputs & Outputs
Analog outputs • 0 … 5/10 V (scalable), min. load 10 kΩ
• 0/4 … 20 mA (scalable), max. load 500 Ω
Digital output Over RS-485:
• Modbus
• Vaisala Industrial Protocol
Operating Voltage
With digital output in use 12 … 30 VDC
With voltage output in use 12 … 30 VDC
With current output in use 20 … 30 VDC
Power Consumption
Typical (continuous operation) 0.4 W
Maximum 0.5 W
Spare Parts & Accessories
Standard membrane filter ASM211650SP
Porous sintered PTFE filter DRW243649SP
Probe cable with open wires (1.5 m) 223263SP
Probe cable with open wires (1.5 m), shielded 254294SP
Probe cable with open wires (3 m) 26719SP
Probe cable with open wires (10 m) 216546SP
Probe cable with open wires and 90° plug (0.6 m) 244669SP
Probe cable with open wires and 90° plug (1.5 m) 255102
Flow-through adapter with gas ports ASM211697SP
Indigo USB adapter 1) USB2
MI70 connection cable for probe CBL210472
Flat cable for GMP250 probes, M12 5-pin CBL210493SP
Probe mounting clips (2 pcs) 243257SP
Probe mounting flange 243261SP
Calibration adapter DRW244827SP
Spray shield ASM212017SP
1) Vaisala Insight software for Windows available at


Vaisala GMP251 CO₂ Probe_DpstarGroup