C-sense in situ pCO₂ Sensor
C-sense™ probes are compact, lightweight sensors for measurement of the partial pressure of gas in liquids. Designed for applications involving immersion in water, oil, or water and oil mixtures, the sensors combine an oil-resistant interface with a compact, temperature-compensated non-dispersive infrared (NDIR) detector. C-sense ships with a copper antifouling guard which minimizes biofouling as well as protects the membrane. Designed for integration,
C-sense enables pCO₂ monitoring at a significantly lower price than
traditional pCO₂ sensors.
Available in 4 standard measurement ranges:
- other ranges available
Accuracy 3% of full scale
Submersible to 600m
Easily integrated: 4-pin analog output
Small size: <2” x 8” and <1lb
Low power consumption: 80mA @ 6V DC
New! Field-replaceable membrane
Accessories & Spare Parts
Frequently Asked Questions
Does the C-sense have to be corrected for hydrostatic pressure?
No. Hydrostatic pressure has no effect.
Does the C-sense need to be corrected for salinity?
No. Salinity has no effect on the C-sense measurement as it is an aqueous measurement.
Does the C-sense need corrections for temperature and total dissolved gas pressure (TDGP)?
The C-sense does not need to be corrected for temperature, it is compensated for in the sensor. However for increased accuracy, it should be corrected for TDGP. Each C-sense is calibrated at 20 degrees C and an atmospheric pressure at or near 101.3kPa (pressure at the time of calibration is stated on the calibration sheet which ships with the C-sense). Corrections can be made, assuming TDGP is known, using the equation below.
Under what conditions should a user measure TDGP?
What kind of error can be expected if TDGP is not measured?
How does the C-sense measure at the specific wavelength absorbed by CO2?
As a proxy to CO2 concentration, absorption of a light source passing through the sample gaseous headspace is measured. In order to limit the wavelengths emitted by the light source to those specific to CO2 absorption, a filter is used.
Does the C-sense sample wet air or dry air?
What is the warm-up time for the instrument?
What it the equilibration time for the instrument?
Equilibration times for pCO2 sensors are often stated as a t63 level. This is defined as the time it takes for the instrument to reach 63% of equilibration. For the C-sense, this value is ~4 minutes.
The equilibration time can be reduced with the use of the Water Pumped Head (P.N. 2400-700).
Can the C-sense be integrated with a SeaBird Electronics CTD?
How often does the C-sense need to be calibrated? If the calibration is a year old, but the instrument has never been deployed, does the instrument need to be recalibrated?
Is bio-fouling an issue for the C-sense and if so, how can it be mitigated?
What material are the screws in the C-sense made of?
What does the 3% "error" mean in relation to the measurement scale of the C-Sense?
The accuracy is plus/minus 3% of the calibration range, not of the measured value. This would be a possible error of 120ppm for 0-4000 range, or 300ppm for 0-10,000 range.
The dissolved oxygen in our system ranges from 50-150% saturation. Is that going to be a source of error if we do not correct for this?
The CO2 detector works by measuring in the gas phase using an IR detector, this method detection is sensitive to the gas pressure inside the IR cell. In most natural waters the dissolved gas pressure is close to atmospheric and the correction for changes in the gas pressure of the cell are very small. In the case of highly fluctuating O2 saturation, the dissolved gas pressure in the water can change dramatically - up to 10% of the total dissolved gas pressure for 50-150% O2 levels. The level of change is not equal to the change in O2 as there may be physical mixing and exchange with the atmosphere that can change N2 levels when O2 is variable. The bigger concern with trying to correct using O2 data is that O2 is much slower to equilibrate across the sensor’s membrane and this can lead to large lag times for changes in gas pressure in the cell when compared to measured O2 changes.