The Model 513D CTD/Multiparameter Probe operates effectively in inland waters, estuarine and coastal environments, and in the open sea. It has also been used for a number of industrial monitoring requirements. A selection of up to ten parameters are offered, including conductivity, temperature, depth, sound velocity, dissolved oxygen, pH, turbidity, redox, and specific ions. Measurements are made simultaneously and continuously.

The Model 513D Probe automatically computes salinity within the probe using an electronic temperature/conductivity compensating circuit which operates over an extremely wide range of salinity. This is of particular value in estuarine research. The conductivity value is also provided so the user may also calculate salinity using the algorithm of his choice.

Construction of the probe is completely modular. Each sensor screws into the base plate of the probe. The signal processing electronics for each parameter is on its own individual printed circuit board. Therefore, parameters may be easily added by the user in the field, thereby expanding the capability of the system. This flexibility has proven to be very valuable to many users when they wish to expand the scope of their research months, or even years after originally purchasing the system. Replacement modular circuit boards and sensors also facilitate trouble shooting and repair.

With the 513D-A/D, an A/D converter is installed in the housing of the multiparameter probe and serial data is output for use with the 514PC-W Data Logging System via a four conductor cable.