Carbon Dioxide Meter

The Carbon Dioxide Meter is a field operated Instrument for measuring CO2 and temperature in both gas and liquid phase. The unit is capable of measuring CO2 from 0.1 to 100%.

Measurement principle

A diaphragm-type glass electrode based on the electrochemical principle is employed for this CO2 gas sensor. According to this principle, when CO2 gas passes through the diaphragm and dissolves in the inner solution, the pH of the solution changes. Because the change of the pH is proportional to the CO2 concentration, the degree of change is measured to determine the CO2 concentration. The following figure indicates the relationship, which exhibits good linearity characteristics, between the CO2 concentration and the electric potential of the glass electrode. If there is a 10-fold change in the CO2 concentration, there is an approximately 60 mV change in the electric potential. Relationship between the CO2 concentration and the electric potential difference of the glass electrode


  • Excellent selectivity: The diaphragm-type glass electrode method is employed to guard against the effects of other mixed gases (except acid gases and basic gases). There is also no need for drying sample because the sensor is relatively unaffected by humidity.
  • Concentration conversion function: You can specify to switch between the gas phase concentration (%(v/v)) and the liquid phase concentration (mg/L).
  • Memory function capable of saving: up to 1,000 data items. Supports auto-save for specified intervals*
  • Short interval memory function: 1 sec. to 99 min. 59 sec.
  • Long interval memory function: 2 min. to 99 hrs. 59 min. (When using the long interval memory function, the switch turns off (enters sleep mode) after measuring concentration for 1 minute. It remains off until the next measurement starts.)
  • Interface for External Devices: (Ability to connect the meter to a personal computer, an external printer, and a recorder.) We also provide special data acquisition sof tware for loading saved measurement data into a personal computer in text format.
  • Waterproof construction ( meter part): IP 67 (enabled when the sensor is connected and on the external I/O ports are masked). The meter part can be submerged at a depth of 1 m for up to 30 min.
  • Ambient temperature/humidity: 0 to 45C , no more than 90% (no condensation)
Carbon Dioxide Meter
Carbon Dioxide Meter


Measuring Method Diaphragm-type glass electrode method
Indication LCD Display
Measuring Range: CO2 Liquid phase : 1.49 to 1490 mg/L
Gas phase : 0.1 to 100%
Temperature: 0 to 50 degrees C.
Display Range: CO2 Liquid phase : 0.000 to 2.020 mg/L, 0.00 to 20.20 mg/L,
0.0 to 202.0 mg/L, 0 to 2020 mg/L
Gas phase : 0.000 to 0.202%, 0.00 to 2.02%,
0.0 to 20.2%, 0 to 202%
Range selection : Automatic/ Manual
Temperature -5.0 to 110.0 degrees
Calibration method Two-point calibration using a standard CO2 solutions or standard gases
Repeatability 5% FS or less (Measurement conducted using standard solutions)
Temperature +/- 0.5 C or less
RS-232C Output RS-232C (non-isolated) : Personal computer or external printer EPS-P30 (optional)
Analog output (non-insulated) : Three output ports for concentration, temperature, and range
Note: Special cable is required to use the RS-232C interface and the analog output port simultaneously. Please contact us for details.
If the sample is grounded, make sure to insulate the RS-232C and analog
output port.
Power Source Two AA alkaline batteries/ nickel hydrogen batteries
Dedicated AC adapter (6 VA, optional) also available
Dimensions / weight Approx. 68 mm (W)~35 mm (H)~173 mm (L)
Weight Meter part : Approx. 280 g (includes batteries)

Note 1: A DKK-TOA stirrer or commercially available stirrer would be needed to use standard solutions for calibrations.

Note 2: The lower (sensing) part of the sensor probe has been designed for immersion into a liquid samples. However, the upped part, around where the cable entry is located, is not suitable for immersion into liquid samples. Therefore the sensor probe should not be completely immersed into liquid samples.

Standard Accessories for CGP-31

CO2 electrode ELX-008 sensor with cable length : 1m (included when full set is ordered)
Calibration cell CGC-202L, 3 pcs
143D044 Powder of CO2 calibration solution
143D045 Ion strength adjuster

Protection cover with shoulder belt

Electrode stand
Electrode holder
AA alkaline battery trial use
Instruction manual

Optional Items

ST-7 Stirrer
EPS-P30 External printer with connection cable
118N063 Analog output cable, 1.5 m
GP-LOG Data acquisition software
118N062 RS-232C connection cable, 2 m
YD-12 AC adapter