CTD-N Technical Manual
page 4
EAR-Controlled Technology Subject to Restrictions Contained on the Cover Page.
Main External Components
The main external components of the CTD-NV are shown in Figure 1. The conductivity, tempera-
ture, and pressure sensors are located on the top end cap. The conductivity sensor is free flushing
with no exposed electrodes that can foul or external fields that can affect calibration. The tempera-
ture sensor is aged and therefore highly stable and is directly in the water flow path of the conduc-
tivity sensor. The pressure sensor is exposed to ambient pressure through a pressure port and an
oil-filled capillary. The oil provides the required pressure coupling and is an electrical insulator that
prevents corrosion due to the dissimilar metal compositions of the transducer and instrument
housing. Capillary action ensures the oil remains contained in the pressure port. A single 4-pin (Di-
rect Reading units) or 6-pin (Battery or External Sensor Interface units) bulkhead connector on the
lower end cap provides RS-232, RS-485 or CMOS TTL level digital communications and inputs ex-
ternal power.
Figure 1.
The Location of the CTD-NV Main External Components
NOTE.
Shown with optional wire bail and with the oil capillary tube installed. The tube extends 1.47
inch from the housing. Make sure that the tube is not blocked when mounting the CTD.
