Level Measurement in Narrow Wells
Small bore wells like those in residential or small commercial settings present unique challenges
for measuring and monitoring ground water levels. Their limited space and method
of construction can introduce problems
not found in wells with larger bores, and
the source of those problems can usually
be traced to three issues.
Liners: Well liners are usually installed to
help prevent leaks that may form in the
casing. If a well liner is present, the sensor
must be inserted inside the liner, otherwise
the sensor may return a false reading.
Obstructions: Small bore wells present a
variety of opportunities for a sensor to become
blocked or stuck in the well. Wiring,
pumps, even rough joints in the casing and
liner may cause the sensor to hang up.
Cascading Water: Water can sometimes enter
the well above the static water level, and
then drip or cascade down the borehole,
causing the sensor to give a false reading.
To counteract these problems, a measuring tube is installed in the well. The measuring
tube is typically a length of slotted ¾" PVC pipe, inserted through an access port in the well
cap and running down through the casing and liner. Traditionally, because of the small inner diameter of the measuring tube, measuring devices have been limited to either a
coaxial level meter (little more than a thin, round wire) or to a flat tape level meter (as the
name implies, a flat, ¾" wide tape) both of which transmit a signal to a buzzer or alarm
when they make contact with the surface of the water. While these solutions are functional,
neither is capable of offering a high degree of level measurement.
An Accurate, High-Tech Alternative:
The AMETEK PMT
Model SST Small Bore Slim-
Line Submersible Level Transmitter provides high
quality, accurate level measurement in a small
package. Its 0.69 inch diameter housing allows the
unit to easily fit into small bore applications like
measuring tubes. The simple design and rugged
construction of the solid state Model SST provides
long lasting service with virtually no maintenance.
The AMETEK PMT Model SST indicates the level of
water or other liquids by continuously measuring hydrostatic pressure via its sensing
element composed of an ion-implanted silicon semiconductor chip with an integrated
Wheatstone Bridge. All of its electronics are mounted in
a lightweight submersible 316 stainless steel housing.
Paired with our Model DDMC Digital Meter/
Controller, the Model SST provides a
highly accurate, trouble-free
level measurement
solution.
See the pdf copy of the
application note here.