The temperature is a basic physical quantity, in
nature all processes with the temperature close correlation. The
temperature sensor is most early develops, applies a broadest kind of
sensor. According to the American instrument academic society's
investigation, in 1990, the temperature sensor market share has
greatly surpassed other sensors. Galileo invents the thermometer
from the beginning of 17th century to start, the people start using
the temperature to carry on the survey. Truly turned the
temperature the electrical signal the sensor is in 1821 invents by the
German physicist match shell, this was the afterwards thermocouple
sensor. After 50 years, another German Simens has invented the
platinum resistance thermometer. In under the semiconductor
technology support, this century developed the semiconductor
thermocouple sensor, PN one after another has tied the temperature
sensor and the integrated temperature sensor. Is corresponding
with it, according to the wave and the material mutual function rule,
has developed acoustics temperature sensor, the infrared sensor and
the microwave sensor one after another.
Below main introduction commonly used thermo-element temperature
sensor. For instance two kind of different material qualities
conductors, if in some interconnection in together, heats up to this
junction, does not heat up the spot in them to be able to appear the
potential difference. This potential difference value with not
hot spots measuring point temperature related, concerns with these two
kind of conductors material quality. This kind of phenomenon may
appear in the very wide temperature range, if precision measuring this
potential difference, does not determine the hot spots ambient
temperature again, may accurately know 加热?temperature.
Because it must have two kind of different material qualities
the conductors, therefore calls it "the thermo-element". The
different material quality makes the thermo-element use to the
different temperature range, their sensitivity is also various.
The thermo-element sensitivity is when refers to 加热?the
temperature change 1 ? output potential difference change quantity.
Says by chance regarding the majority metal material strut
thermoelectricity, this value approximately in 5 ~ 40 微伏/?
between.
As a result of the constitution thermo-element metal material
may 耐受 the very high temperature, for example the tungsten rhenium
thermo-element be able to work in 2,000 ?above high temperature,
frequently uses for to examine the high temperature environment the
hot physical parameter, but also some materials can work under the low
temperature, for example the golden iron thermo-element can work in
nearby the fluid nitrogen temperature. Obviously the
thermocouple sensor can work in the very widespread temperature range.
The thermocouple sensor has own merit and the flaw, its
sensitivity quite low, is easy to receive the environment unwanted
signal the influence, also is easy to receive the pre-amplifier
temperature drifting the influence, therefore does not suit the survey
small temperature change. Because the thermo-element temperature
sensor sensitivity thick thin has nothing to do with with the
material, also can make the temperature sensor with the extremely thin
material. Also because the manufacture thermo-element metal
material has the very good ductility, this kind of slight temperature
element has the extremely high speed of response, may survey the fast
change the process, like burning and detonation process and so on.
Said to the general industrial application, in order to protect
the feeling warm part to avoid receiving the corrosion and the
attrition, always installs inside the thick protective covering, the
outward appearance appears stupidly is big, also is much slower
regarding the temperature field response. Use thermo-element
time, must eliminate the ambient temperature the undulation to the
influence which surveys brings. Some put its free electricity in
the invariable temperature field, some use cold end compensators
counterbalance this kind of influence. When the measuring point
is far away the measuring appliance, but also needs to use the hot
spot potential rate and the thermo-element close wire transmits the
signal, this kind of wire is called compensates the wire.
The temperature sensor is in all kinds of each kind of sensor
the most commonly used one kind, the modern temperature sensor contour
extremely slightly, like this even more lets it widely apply in
production practice each domain, also has provided the innumerable
conveniences and the function for ours life.
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