Xylem H-312-22 - Manual (Page 11)

H-312
Installation 2-3
protect the sensor cable so it remains at the temperature of the surrounding air and is not heated
directly by the sun.
2.4 Stilling Wells
The H-312 can be hung in well bores, stilling wells and stand-
pipes. The H-312 should be installed by suspending the sensor
using a small stainless steel cable, not by its polyurethane
electrical cable. A weighted ballast or sinker, such as the one
that is provided will pull the cable tight at the desired depth and
will help the sensor to hang straight down. The stainless cable
and the miscellaneous hardware can be purchased from Design
Analysis Associates, or from a number of other sources.
The polyurethane cable has internal kevlar strength members
however, the plastic cable construction has a large thermal
coefficient of expansion. This coupled with the fact that the
cable will stretch with applied weight, make the use of the
stainless steel drop cable necessary for all precision
measurements.
Attach one end of the stainless steel support cable to the
support bail on the sensor and fasten the other end to a fixed
reference point at the surface. Attach the ballast to the sensor
using the stainless steel ring on the bottom nose of the sensor.
When installing the H-312 in wells or stand pipes, make certain
the surface of the water in the pipe is open to the atmosphere.
Well pipes are often capped with a sanitary well seal or locking
cap, make certain the well cap has a suitable hole or screened
vent.