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Definition, Products Informations:
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Thermocouple - In electronics and in electrical engineering,
thermocouples are a widely used type of temperature sensor and can also be used
as a means to convert thermal potential difference into electric potential difference.
They are cheap and interchangeable, have standard connectors, and can measure a
wide range of temperatures. The main limitation is accuracy; system errors of less
than one degree Celsius (°C) can be difficult to achieve.
Thermostat - A thermostat is a device for regulating the temperature
of a system so that the system's temperature is maintained near a desired setpoint
temperature. The thermostat does this by controlling the flow of heat energy into
or out of the system. That is, the thermostat switches heating or cooling devices
on or off as needed to maintain the correct temperature. Thermostats can be constructed
in many ways and may use a variety of sensors to measure the temperature. The output
of the sensor then controls the heating or cooling apparatus.
PLC Controller - A programmable logic controller (PLC), or programmable
controller is a digital computer used for automation of industrial processes, such
as control of machinery on factory assembly lines. Unlike general-purpose computers,
the PLC is designed for multiple inputs and output arrangements, extended temperature
ranges, immunity to electrical noise, and resistance to vibration and impact. Programs
to control machine operation are typically stored in battery-backed or non-volatile
memory. A PLC is an example of a real time system since output results must be produced
in response to input conditions within a bounded time, otherwise unintended operation
will result.
Thermometer - is a device that measures temperature or temperature
gradient, using a variety of different principles. The word thermometer is derived
from two smaller word fragments: thermo from the Greek for heat and meter also from
Greek, meaning to measure. A thermometer has two important elements, the temperature
sensor (e.g. the bulb on a mercury thermometer) in which some physical change occurs
with temperature, plus some means of converting this physical change into a value
(e.g. the scale on a mercury thermometer). Industrial thermometers commonly use
electronic means to provide a digital display or input to a computer.
Type T (copper–constantan) thermocouples are suited for measurements
in the −200 to 350 °C range. Often used as a differential measurement since only
copper wire touches the probes. As both conductors are non-magnetic, type T thermocouples
are a popular choice for applications such as electrical generators which contain
strong magnetic fields. Type T thermocouples have a sensitivity of about 43 µV/°C.
Type C (tungsten 5% rhenium – tungsten 26% rhenium) thermocouples
are suited for measurements in the 0 °C to 2320 °C range. This thermocouple is well-suited
for vacuum furnaces at extremely high temperatures and must never be used in the
presence of oxygen at temperatures above 260 °C.
Definitions and informations about our progucts - thermo sensors, thermocouples,
thermocluple, sensor, calibrators, digital measurement. thermocouples, wire, compensatory,
wires, thermocouple, pt100, thermo, sensor, sensors, regulator, converter, calibrator,
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Thermowells, RTDs, Thermosensors Manufacturing, Cerampak, Cold Junction Terminations
, Hot Junction Terminations , Thermowells, RTDs, Resistance Temperature Detectors,
Thermocouple Wire, Thermo Sensors Manufacturer |
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Informations, Definitions:
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A variety of thermocouples are available, suitable for different measuring applications.
They are usually selected based on the temperature range and sensitivity needed.
Thermocouples with low sensitivities (B, R, and S types) have correspondingly lower
resolutions. Other selection criteria include the inertness of the thermocouple
material, and whether or not it is magnetic. The thermocouple types are listed below
with the positive electrode first, followed by the negative electrode.
Type K (chromel–alumel) is the most commonly used general purpose
thermocouple. It is inexpensive and, owing to its popularity, available in a wide
variety of probes. They are available in the −200 °C to +1200 °C range. The type
K was specified at a time when metallurgy was less advanced than it is today and,
consequently, characteristics vary considerably between examples. Another potential
problem arises in some situations since one of the constituent metals, nickel, is
magnetic. The characteristic of the thermocouple undergoes a step change when a
magnetic material reaches its Curie point. This occurs for this thermocouple at
354°C. Sensitivity is approximately 41 µV/°C.
Type E (chromel–constantan) has a high output (68 µV/°C) which
makes it well suited to cryogenic use. Additionally, it is non-magnetic.
Type J (iron–constantan) is less popular than type K due to its
limited range (−40 to +750 °C). The main application is with old equipment that
cannot accept modern thermocouples. J types cannot be used above 760 °C as an abrupt
magnetic transformation causes permanent decalibration. The magnetic properties
also prevent use in some applications. Type J thermocouples have a sensitivity of
about 50 µV/°C.
Type N (nicrosil–nisil) thermocouples are suitable for use at high
temperatures, exceeding 1200 °C, due to their stability and ability to resist high
temperature oxidation. Sensitivity is about 39 µV/°C at 900°C, slightly lower than
type K. Designed to be an improved type K, it is becoming more popular.
Types B, R, and S thermocouples
use platinum or a platinum–rhodium alloy for each conductor. These are among the
most stable thermocouples, but have lower sensitivity, approximately 10 µV/°C, than
other types. The high cost of these thermocouple types makes them unsuitable for
general use. Generally, type B, R, and S thermocouples are used only for high temperature
measurements. Type B thermocouples use a platinum–rhodium alloy for each conductor.
One conductor contains 30% rhodium while the other conductor contains 6% rhodium.
These thermocouples are suited for use at up to 1800 °C. Type B thermocouples produce
the same output at 0 °C and 42 °C, limiting their use below about 50 °C. Type R
thermocouples use a platinum–rhodium alloy containing 13% rhodium for one conductor
and pure platinum for the other conductor. Type R thermocouples are used up to 1600
°C. Type S thermocouples use a platinum–rhodium alloy containing 10% rhodium for
one conductor and pure platinum for the other conductor. Like type R, type S thermocouples
are used up to 1600 °C. In particular, type S is used as the standard of calibration
for the melting point of gold (1064.43 °C). |
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