ADS Environmental Services Model 4000 530017 A0 - Manual (Page 36)

Monitor and Sensor Installation 3-13
Although the spreader mechanism fits snugly against the inside of
the ring, the spreader mechanism may seem loose on the hex nuts.
Do not be concerned. The spreader mechanism will tighten once
the ring is installed and tightened inside the pipe. The following
picture displays how a properly assembled ring should look.
Properly attached spreader mechanism
Mounting the Sensors to the Ring
The following sections provide instructions on mounting the
ultrasonic depth, velocity, and pressure depth sensors to the ring.
To ensure the most accurate flow data, standard pipe installations
require proper positioning of the sensors on the ring as well as in
the pipe. When facing the downstream edge of the ring, the sensors
should be mounted on the ring in the following locations:
Ultrasonic Depth Sensor Twelve o'clock position (top of
the pipe) when the spreader mechanism is in the one o'clock
position
Doppler Velocity Sensor As close as possible to the six
o'clock position (bottom), provided it is mounted above the
level of any silt present at the bottom of the pipe (Any silt
covering the sensor could interfere with the sensor signals,
potentially producing inaccurate or erroneous readings.)