• Small and light with large memory capacity
  • Seven-electrode cell
  • Anti-fouling piston-type wiper
  • High resolution
  • Non-volatile flash memory
  • Built-in calendar/time information
  • Direct connection to PC
  • Programmable calibration factors
  • Convenient Windows software
  • Robust titanium housing
Picture of sensor
The COMPACT-CTW is a micro-controller equipped miniature and precise data logger that is suitable for long-term, stable deployments.
Conventional salinity sensors are susceptible to measurement degradation from contaminants and bio-fouling. In order to acquire consistent data over long-term deployments, frequent maintenance is required. In the case of the COMPACT-CTW, external contaminants and bio-fouling do not affect measurement performance. Moreover, since a piston-type wiper cleans the sensor before each measurement, stable measurements are acquired without the need for frequent maintenance.
Our state-of-the-art technology allows for a compact design capable of storing up to 178,439 sets of 3-channels of data (temperature, conductivity and wiper status).
The non-volatile flash-memory prevents data loss in case of power failure or irregular battery voltage. The operation of the COMPACT-OPTODE is managed through a PC's RS232-C port. The main unit records calendar and time information with each sample and the sensors' calibration coefficients are stored in the built-in memory. The basic measurement setup requires only the selection of the start time and the measurement parameters.
Data transfer after completion of deployment is easy. Since measurement start time and calibration coefficients are automatically transferred to the data acquisition software together with the measured data, it is not necessary to manually manipulate the data after download and data processing can be started immediately.
The data processing program offers clear and logical screens for easy operation.
Main Unit Specifications Sensor condition after retrieval
Parameter Temperature Conductivity
Type Thermistor Seven-electrode sensor
Range -5 to 45 XC 0 to 60 mS/cm
Resolution 0.001 XC 0.003 mS/cm
Accuracy 0.05 XC 0.05 mS/cm
Memory type 2 Mbyte non-volatile flash memory
Capacity 178,439 data
A/D conversion 16 bits digital conversion
Interval 2,5,10,15,20,30 seconds
Burst time 1 to 255 minutes
Sampling number 1,10,15,20,30,60,120,180,240,300,600,1200
Battery capacity Lithium battery 14 Ah
Power consumption 60 mA during measurement
170 mA - 220 mA during wiper extension
50 mA -100 mA during wiper return
Materials Titanium
Size 60 mm dia., 431 mm in total length
Weight 1,800 g in air & 800 g in water
Depth rating 100 m
Field data Salinity comparison between COMPACT-CT & CTW

The above graph shows the results of a field test at Nomi Bay, Kochi Pref. from Feb. to Mar., 2004. The green line indicates data measured by a conventional COMPACT-CT (non-wiper) and the blue line by the COMPACT-CTW. The instruments were kept at 1m depth. The picture above is of the COMPACT-CTW after retrieval which shows the amount of growth on the instrument.
The data from both units matched for one week. After 170 hours of deployment, the salinity data of the CT instrument departed significantly from the CTW measurement. After 240 hours of deployment, the CT's salinity values show erratic excursions. After 700 hours, the average difference between the salinities reported by the CTW and CT instruments exceeded 4 PSU, which is approximately 12% of the expected salinity value.