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What Is A Tilt Sensor?
The phrase 'tilt sensor' is a term, which has been
widely used, and misused over the years. It is
frequently employed in a generic fashion to describe a
large variety of devices, which either measure,
indicate, or otherwise provide a signal of some type,
when tilted from (or to) a level position, using gravity
as a reference. While a number of these devices are
indeed tilt sensors, the others fall into various
categories, which by their very definition negate their
inclusion. However, to make a distinction as to what
actually qualifies a device as a true tilt sensor, we
must first understand what one is.
A tilt sensor can be defined as ‘a device, which
produces an electrical output that varies with angular
movement’. Though brief and rudimentary, this
definition plainly makes two pertinent points: the
device must have an electrical output, and that the
electrical output must vary when tilted. With this
understanding, all visual/mechanical devices such as
‘ball-in-tube’ style slope indicators, pendulum
protractors and bubble levels for that matter, are
automatically eliminated. Also eliminated are devices,
which use mercury switches and/or electro-mechanical
triggers that strictly deliver on-off type outputs.
Within the sensor industry, the term ‘tilt sensor’
becomes a bit finer. Normally it will refer strictly to the
sensing element itself, devoid of any input/output
conditioning electronics. Once conditioning electronics
are added, the aggregate device then becomes known as an
inclinometer. Although both have an electrical output,
which varies with angular movement, this distinction is
commonly recognized.
Types Of Tilt Sensors And Inclinometers
There are many types of tilt sensors and
inclinometers available on the market today, some
whose history extends back more than 50 years.
There are three major categories, which encompass
the majority of types available. They are force
balanced, solid state (MEMS) and fluid filled.
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Within each category there are many variations,
each having their own advantages and
disadvantages. For example, the force balanced
variety generally provides superior performance,
but comes at a substantially higher cost. The
MEMS based devices feature integral signal
conditioning and relative ease of installation.
However, thermal coefficients are extremely
high, and significant compensation is normally
required to obtain acceptable accuracy in most
applications.
The fluid filled variety of tilt sensors comprises
the largest industrial market sector by far. This is
primarily due to the relative low cost to
performance ratio. Within this genre we find
primarily electrolytic and capacitive technologies.
While limited in terms of response time, the
majority of applications are effectively static,
rendering this attribute moot.
Electrolytic Tilt Sensors
The most enduring of all tilt sensors to date is
the electrolytic type. Pre-dating World War II,
this sensor’s roots extend back to the Genesis of
electronic tilt sensing. Spectron Glass and
Electronics, who effectively pioneered this
industry, developed many of the electrolytic tilt
sensors to first hit the marketplace. The basic
design and operating principles originally
employed are still valid, and continue to be
widely used today. This technology is unique in
the fact that it lends itself to both narrow and
wide angular range measurements, while
maintaining compact size and high accuracy. This
capability has enabled servicing of a diverse
range of markets. Comparatively, the other fluid
filled technologies available are bulky, and
cannot achieve high accuracy over shallow
angular ranges.
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