Membrane-Covered Optical CO2 Sensor for Monitoring Dissolved Carbon Dioxide in Water

Reference: T28ACO2

Dissolved carbon dioxide (excluding HCO3- and CO32-) ranks among the key parameters in water monitoring. The T28ACO2 is a new membrane-covered optical CO2 sensor in a titanium housing, with a number of improved characteristics.

It is rated for depths of up to 1,000 m, offers analog or digital output, draws less current and compensates for temperature automatically inside the sensor. It can be interfaced externally with CTD probe systems or in-house measuring systems, or run as a stand-alone sensor.

What it measures

Price on request

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T28ACO2

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Overview

How it measures

A gas-permeable silicone membrane keeps the sample away from the sensor's inner volume, blocking liquids and solids. Once the sensor is immersed, the CO2 partial pressure equalizes between the inner volume and the sample, and an optical sensor mounted inside reads it using single-beam dual-wavelength NDIR. To work out the carbon dioxide concentration, this partial pressure reading must be combined with the water temperature and the air pressure.

Compared with the so-called m-method, the optical sensor has an edge: a comparison showed no signal interference from silicate, phosphate, HCO3- or CO32-.

Key features

Submersible direct-reading sensor for natural waters, industrial waters and seawater
Detects CO2, and total inorganic carbon when pH is measured as well
No signal interference from silicate, phosphate, HCO3- or CO32-
Built-in reference measurement for superior stability
Calibration coefficients stored in the sensor
Rated for depths of up to 1,000 m
Power consumption below 0.5 W
Analog or digital output
Internal temperature compensation
Compensation for humidity and other influences
Heated sensor head that prevents condensation

Technical data

Carbon dioxide

Measuring range (choose one): 15 mg/l, 50 mg/l or 340 mg/l; others on request
Accuracy by range:
- 0...5 mg/l CO2: ± 0.06 mg/l
- 5...15 mg/l CO2: ± 2 % of reading
- 15...50 mg/l CO2: ± 3.5 % of reading
- 50...80 mg/l CO2: ± 1.5 mg/l CO2
- 80...340 mg/l CO2: ± 6 mg/l CO2

General

Size: 225 mm long, 33 mm in diameter
Housing: titanium
Connector: SubConn MCBH4M
Supply: 12-30 V DC with the digital or voltage output; 20-30 V DC with the current output
Consumption: < 0.5 W
Warm-up: < 12 seconds, < 2 minutes to full accuracy
Maximum deployment depth: 1,000 m/1,000 dbar
Outputs: 4...20 mA, 0...5 V DC or RS485 digital
Storage and measurement temperature: 0...60°C
Internal temperature compensation
Compensation for humidity and other influences