Idronaut CDT 302 Probe

The Idronaut CDT 302 probe is a 50 mm diameter water quality probe which measures pressure, temperature, fluid conductivity (dual range), pH, dissolved oxygen, and oxidation-reduction potential (redox) Salinity is calculated automatically using temperature, conductivity, and pressure, using the UNESCO formula. Different sensor arrangements exists.

The Idronaut probe is modified to operate on the MGX II digital logger. The modification includes a new downhole power supply and FSK modem. This allows the MGX II to power the probe and communicate with the Idronaut probe. The probe is powered with 50 VDC, and sends data to the surface at 9600 baud, even parity, 8 data bits, and one stop bit.

The probe comes in various pressure ratings, ranging from 300 dbar to 1500 dbar.

The CDT 302 Multi-Parameter Probe has been specifically designed for borehole application and uses very reliable, accurate and drift free high quality sensors, associated with advanced and miniaturised electronics. Integration of geographical position information, through GPS, and acquired data can be performed by means of the IDRONAUT probe management software.

High Performance combined Temperature and Conductivity Sensors

Temperature Sensor

Features a very fast platinum resistance thermometer (time constant: 50 ms). Negligible self-heating effect.

Flow Conductivity Sensor
Features a very large diameter, seven-ring quartz cell which does not require platinum black deposition and which can be cleaned without re-calibrating.

Oxygen Sensor
Features an innovative pressure-compensated polarographic sensor, with a replaceable cap for membrane support. Stirring effects are negligible.

pH Glass Sensor (7000 m)
Cylindrical, high-pressure glass membrane pH electrode in conjunction with a special differential amplifier system.

Oxidation-Reduction Potential (ORP) Sensor
Special cross section platinum electrode.

Solid Gel Reference Electrode
A reference electrode for pH and oxidation-reduction potential measurements. It uses a special ceramic junction-less design. Operation to 7000 m. Long life.

Data Transmission
Via MSI Modem

Internal Memory
Provides up to 1,500 data acquisitions each of 8 channels.

Dimensions And Weight
50 mm diameter x 650 mm length; 2,3 kg in air.

Optional Sensors
- Calcium, Copper, CO 2, Nitrate, Ammonia and Chloride

All sensors have extremely low time constants (50 milliseconds for physical parameters [CTD] and 3 seconds for chemical parameters). The slim line of the Probe and the pressure-compensation of sensors permit operation in fast water profiling or in fixed depth monitoring down to 1500 metres depth. Scanning of the sensors takes place at a rate of 25 milliseconds. The user can decide to perform spot measurements or to acquire data which are the average of a certain number of sensor scans; said number is selectable through the Probe software. The electronic boards are fitted in an AISI 316 stainless steel sealed housing; one oceanographic connector, located on the top cover, provides the probe power supply and data exchange with a suitable external device. On the opposite end, the sensor area is protected against accidental bumps with an AISI 316 stainless steel protective cage. The CDT 302 PROBE is microprocessor-controlled, and measures and transmits sensor data through the shielded coaxial cable via MSI Modem (real-time monitoring mode), or stores measurements in the internal memory for trans-mission later. A special mode of operation allows fast data acquisition, at a rate of 40 measurements per second, so that micro-profiles can be easily obtained. Moreover, Timed Data Acquisition allows acquisition and transmission at program-mable time intervals. The internal non-volatile memory can store up to 1,500 measurements, each composed of 8 parameters. A friendly menu-driven MMI (Man Machine In-terface) allows the operator to interact with the internal firmware to person-alize the operating functions and to perform the sensor calibration. Com-mands are selected from a list, or a menu, of possible choices. Parallel to the menu interface, a computer-oriented interface has been implemented, allowing execution of the data acquisition and transmission to be performed in a quick and efficient (from a Computer’s point of view) way. The CDT 302 Probe is equipped with an MSI Modem system (4,800 bps) that allows the connection of the Probe to the Portable Deck Unit by means of a coaxial armoured cable (2 wires). The cable also provides the mechanical support of the Probe and its power supply.

Sensor Specifications

Time Constant
0.....1500 dbar*
0.25% full scale
0.1 dbar 
50 ms
-1 ... +49 ° C
0.02 °C 0.00
50 ms
0..... 62 mS/cm**
0.02 mS/cm
0.004 mS/cm
50 ms(at 1 m/second flow rate )
0..... 50 ppm
0.1 ppm
0.01 ppm
3 s (in air)

0... 500% sat.
1% sat.
0.1% sat.
3 s
0..... 14 pH
0.05 pH
0.01 pH
3 s
-1000 to + 1000 m
V 10 m
V 1 mV
3 s
0 to 100 mg/l-N
greater of ±5% of reading or ±2 mg/l-N
0.01 mg/l-N
* other standard pressure transducers available have 20, 70 and 300 dbar ranges.
** a probe version with conductivity range for fresh water is also available:

Electronic specifications

Sampling frequency:  up to 40 Hz.
Data output rate: up to 2 Hz.
Communication: MSI Modem
Communication protocol: proprietary byte-oriented message protocol.
Memory: 32 Kbytes.
Power supply: 10 .. 30 V, 50 mA @ 12V, 600 mW.
Dual mode user interface: [MENU] friendly menu-driven user interface
[PACKET] message-driven interface allow operations from a PC.

Onboard electronics
CPU:  Z80180, 8 bit microcontroller unit.
Program memory: 32 KByte EPROM
Memory: 32 KByte nonvolatile SRAM.
A/D Converter: 14 bit 366,2 mV/bit successive approximation.
Analog inputs: 8 multiplexed analog input channels.

Mechanical specifications
Dimensions: cylinder diameter: 50 mm / total length: 600 mm
Weight: in air: 2.2 Kg / in water: 1.0 kg

Ordering Information
Order Number
Idronaut CDT 302  530-400-IDRO