CO₂ Probe GMP251 CO₂ Probe GMP251
CO₂ Probe GMP251

Vaisala GMP251 Percentage-Level CO₂ Probe

Vaisala GMP251 Percentage-Level CO₂ Probe

The Vaisala GMP251 is an intelligent probe for stable percentage-level carbon-dioxide measurement in incubators, controlled-atmosphere storage and demanding industrial applications.

  • CO₂ measurement range from 0 to 20% CO₂
  • Accuracy of ±0.1% CO₂ at 5% CO₂
  • Compensation for temperature, pressure, humidity and oxygen
  • Heated sensor head helps prevent condensation
  • 0–20 mA, 4–20 mA, 0–5 V, 0–10 V and RS-485 output options
  • Standalone Modbus RTU operation or connection to an Indigo transmitter
  • Compatible with Vaisala Indigo80 and Insight PC software
  • IP65 probe body with traceable calibration certificate

Percentage-Level CO₂ Measurement for Demanding Applications

The Vaisala GMP251 is designed for applications where carbon dioxide is measured in percentage rather than normal ambient-air ppm levels. Typical uses include life-science incubators, controlled-atmosphere storage, fruit and vegetable transportation, cold rooms, greenhouses and industrial chambers.

Its second-generation Vaisala CARBOCAP® sensor combines an internal reference with a durable infrared light source for stable long-term measurement. The probe can operate independently with analogue or Modbus RTU output, or connect to a Vaisala Indigo transmitter for a local display, relays and additional system interfaces.

Range selection: Choose GMP251 for percentage-level CO₂ up to 20%. For ppm-level applications such as demanding HVAC, refrigeration or plant-growth equipment, use the Vaisala GMP252.

GMP251 Measurement Performance

SpecificationGMP251
Measurement range 0 to 20% CO₂
Accuracy at 5% CO₂ ±0.1% CO₂
Accuracy from 0 to 8% CO₂ ±0.2% CO₂
Accuracy from 8 to 20% CO₂ ±0.4% CO₂
Typical calibration uncertainty at 5% CO₂ ±0.07% CO₂
Typical calibration uncertainty at 20% CO₂ ±0.27% CO₂
Start-up time at +25 °C Less than 10 seconds
Warm-up time for full specification Less than four minutes
Response time with standard filter Less than one minute, T90
Sensor technology Vaisala CARBOCAP® non-dispersive infrared sensor

The accuracy values apply at +25 °C and 1013 hPa and include repeatability and non-linearity. Configure the environmental compensations correctly when temperature, pressure, humidity or oxygen concentration differs from the reference conditions.

Why Environmental Compensation Matters

InfluenceGMP251 capabilityApplication guidance
Temperature Integrated temperature measurement or a configured fixed value Use the integrated compensation when chamber temperature changes during normal operation
Pressure Configurable compensation from 500 to 1100 hPa Enter the actual process pressure when accurate percentage-level measurement is required
Humidity Water-vapour compensation over 0 to 100 %RH Humidity affects gas composition and should be included when conditions vary
Oxygen Configurable background-gas compensation from 0 to 90% O₂ Particularly important in modified-atmosphere or unusual gas mixtures

A probe can be correctly calibrated yet still show an unsuitable process value if its pressure or background-gas compensation is wrong. Record the compensation settings as part of commissioning and validation documentation.

Inputs, Outputs and Mechanical Specifications

SpecificationGMP251
Voltage output Scalable 0–5 V or 0–10 V; minimum load 10 kΩ
Current output Scalable 0–20 mA or 4–20 mA; maximum load 500 Ω
Digital output RS-485 with Modbus RTU or Vaisala Industrial Protocol
Supply with digital or voltage output 12 to 30 V DC
Supply with current output 20 to 30 V DC
Power consumption 0.4 W typical; 0.5 W maximum
Operating temperature −40 to +60 °C
Operating humidity 0 to 100 %RH, non-condensing
Operating pressure Below 1.5 bar
Probe-body protection IP65
Probe dimensions 25 mm diameter and 96 mm length
Weight Approximately 42 g
Electrical connector M12 5-pin male

Typical GMP251 Applications

ApplicationWhy GMP251 fitsInstallation consideration
Life-science incubators Accurate measurement around common percentage-level CO₂ setpoints Review sterilisation temperature and probe exposure; GMP231 may suit direct incubator integration
Controlled-atmosphere storage Measures elevated CO₂ used to manage stored produce Configure oxygen, humidity and pressure compensation for the gas mixture
Cold storage and transport Wide operating-temperature range and IP65 probe body Prevent liquid condensation and protect the cable connection
Greenhouses and cultivation Stable monitoring where CO₂ enrichment reaches percentage levels Confirm whether the actual range is percentage or ppm before selecting GMP251
Environmental chambers Compact standalone probe with analogue and digital connectivity Choose a mounting flange, clip, probe holder or flow-through arrangement
OEM equipment M12 connection and configurable outputs support equipment integration Design for service access, environmental compensation and future calibration

Vaisala GMP251 or GMP252?

Selection pointGMP251GMP252
Primary range 0 to 20% CO₂ 0 to 10,000 ppm CO₂
Extended measurement Percentage-level measurement up to 20% Can measure up to 30,000 ppm with reduced accuracy
Best suited to Incubators, controlled atmospheres, cold storage and percentage-level processes Demanding HVAC, refrigeration, agriculture and ppm-level process measurement
Typical accuracy point ±0.1% CO₂ at 5% CO₂ ±40 ppm from 0 to 3000 ppm
Environmental compensation Temperature, pressure, humidity and oxygen Temperature, pressure, humidity and oxygen
Standalone outputs Voltage, current or RS-485 Voltage, current or RS-485
Indigo compatibility Indigo200, Indigo300, Indigo500 and Indigo80 Indigo200, Indigo300, Indigo500 and Indigo80
Choose this model when The expected concentration is normally above the ppm-level range The expected concentration is expressed in ppm and remains below the probe's useful range
Product information GMP251 is detailed on this page Explore Vaisala GMP252

Use GMP251 Standalone or with an Indigo Transmitter

ConfigurationConnection and outputsRecommended when
GMP251 standalone Direct analogue or Modbus RTU connection No local display, relay or additional transmitter enclosure is required
Indigo200 Series One probe with display, analogue or Modbus RTU model and two relays A standard industrial transmitter and local interface are required
Indigo300 One probe, IP66 metal enclosure and three analogue outputs A rugged analogue-focused installation is preferred
Indigo510 One probe, two isolated analogue outputs, Ethernet and Modbus TCP A premium single-probe system with web access is required
Indigo520 Two probes, four isolated analogue outputs, two relays, Ethernet and Modbus TCP GMP251 must be combined with another compatible probe or additional control functions
Product information Explore Vaisala Indigo200   Explore Vaisala Indigo300   Explore Vaisala Indigo510 and Indigo520

Portable Measurement with Indigo80 and GMP80P

GMP251 can connect to the Vaisala Indigo80 for portable display, configuration, logging, diagnostics and calibration. For pump-aspirated sampling through an incubator port or sample tube, the GMP80P combines the GMP251 measurement probe with a portable pump arrangement.

Explore Vaisala Indigo80 and GMP80P

Calibration and Maintenance

GMP251 supports one-point or two-point CO₂ adjustment. Calibration and configuration can be performed through Vaisala Insight PC software, a compatible Indigo transmitter, Indigo80 or supported MI70 equipment. The optional DRW244827SP adapter allows reference gas to be applied to the probe during calibration.

  • Use certified reference gases that cover the application range and required uncertainty.
  • Enter the correct environmental compensation values during calibration.
  • Allow the measurement to stabilise before recording or adjusting each point.
  • Inspect and replace the filter when contamination or damage affects response.
  • Set the calibration interval according to process criticality, exposure and quality requirements.
  • Record the reference-gas certificates, as-found result, adjustment and as-left result.

Vaisala GMP251 Supplier and Technical Support in Malaysia

Seacom Process Instruments supplies and supports the Vaisala GMP251 Percentage-Level CO₂ Probe in Malaysia for incubators, life-science equipment, controlled-atmosphere storage, cold-chain applications, environmental chambers and demanding industrial processes.

Our team can help confirm whether GMP251 or GMP252 is appropriate, select the standalone output or Indigo transmitter, specify cables and mounting accessories, and review temperature, pressure, humidity and oxygen compensation. We can also assist with Indigo80/GMP80P portable sampling, commissioning and calibration planning.

Selecting a GMP251 configuration? Send us the normal and maximum CO₂ concentration, temperature, pressure, humidity, oxygen level, installation method, output signal, controller interface and calibration requirement.

Download

  GMP252 Catalogue   (172.51k)

  GMP251 Catalogue   (218.45k)

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