CTD-N Technical Manual
P/N 95F-6000-00 (February 2017)
page 1
EAR-Controlled Technology Subject to Restrictions Contained on the Cover Page.
CTD-N Technical Manual
Introduction
The Teledyne RD Instruments CTD-N (includes CTD-NV, CT-NV, CTD-NH, and CT-NH models) is
a ruggedized, extremely durable sensor that is designed to collect high precision, scientific quality
salinity data by measuring conductivity, temperature, and pressure. The instrument measures con-
ductivity using a patented inductively coupled highly stable NXIC (Non-eXternal Inductive Conduc-
tivity) sensor that is designed for long term, low maintenance deployments, even in coastal regions
where biological fouling is a problem. Temperature is measured with an aged, high accuracy ther-
mistor mounted directly in the water flow path of the conductivity sensor. On CTD models, pressure
is measured using a fully temperature compensated precision micro-machined silicon transducer.
The CTD-N optionally includes four additional DC input channels and an RS-232 channel. Included
with this option are additional connectors for connecting external sensors. The DC input channels
interface with 0–5 VDC output sensors, including dissolved oxygen, pH, chlorophyll, light trans-
mission, and others. The RS-232 channel interfaces with many external sensors via an RS-232 se-
rial connection. Two of the DC channels include two logic outputs for controlling sensor gains or
other sensor functions. The CTD-N also provides power for the sensors.
Measured conductivity, temperature and pressure data, along with calculated salinity and sound
velocity and external sensor data, are continuously recorded to internal memory at selectable sam-
ple rates from 1 to 15 Hz. For each sample, the time and date are also recorded. All data are saved to
a file which can be downloaded to a computer after retrieval of the instrument. Multiple files for
multiple deployments can be recorded to memory and downloaded separately.
The CTD-N is configured using CTDPro, a Microsoft Windows® based software program included
with the instrument. With CTDPro you can configure and deploy the instrument, download and
save the data from the instrument, view and print graphs of the data, and export the data to a text
or spreadsheet file. In addition, the data can be exported to CTDPost, a post processing software
program available from TRDI that provides a means of processing, displaying, graphing, printing,
and saving processed CTD data.
Maximum Operating Depth
IMPORTANT!
The CTD-N is rated for a maximum operating depth that is based on the pressure
transducer selected. Consult the manufactured configuration sheet supplied with the instrument for
