{"id":4139,"date":"2020-12-11T20:57:56","date_gmt":"2020-12-11T20:57:56","guid":{"rendered":"http:\/\/www.minco.com\/?post_type=resources&p=4139"},"modified":"2024-03-11T13:12:54","modified_gmt":"2024-03-11T13:12:54","slug":"temperature-sensor-faq","status":"publish","type":"resources","link":"https:\/\/www.minco.com\/resources\/temperature-sensor-faq\/","title":{"rendered":"Temperature Sensor FAQ"},"content":{"rendered":"\t\t
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TEMPERATURE SENSOR FAQ<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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The most commonly asked questions regarding Sensors.<\/p><\/div>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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\n\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/i><\/span>\n\t\t\t\t\t\t\t\t<\/i><\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t\t\t\tRTD, Thermocouple, or Thermistor?<\/a>\n\t\t\t\t\t<\/div>\n\n\t\t\t\t\t
Resistance temperature detectors (RTDs)<\/span><\/h5>

An RTD sensing element consists of a wire coil or deposited film of pure metal. The element\u2019s resistance increases with temperature in a known and repeatable manner. RTDs exhibit excellent accuracy over a wide temperature range and represent the fastest growing segment among industrial temperature sensors. Their\u00a0 advantages include:
\u2022 Temperature range: Minco models cover temperatures from -260 to 650\u00b0C (-436 to 1202\u00b0F).
\u2022 Repeatability and stability: The platinum resistance thermometer is the primary interpolation instrument used by the National Institute of Standards and Technology from -260 to 962\u00b0C. Ordinary industrial RTDs typically drift less than 0.1\u00b0C\/year.
\u2022 Sensitivity: The voltage drop across an RTD provides a much larger output than a thermocouple.
\u2022 Linearity: Platinum and copper RTDs produce a more linear response than thermocouples or thermistors. RTD non-linearities can be corrected through proper design of resistive bridge networks.
\u2022 Low system cost: RTDs use ordinary copper extension leads and require no cold junction compensation.
\u2022 Standardization: Manufacturers offer RTDs to industry standard curves, most commonly 100\u00a0\u03a9 platinum to EN60751 (Minco element code PD or PE).<\/p>

Thermocouples<\/span><\/h5>

A thermocouple consists of two wires of dissimilar metals welded together into a junction. At the other end of the signal wires, usually as part of the input instrument, is another junction called the reference junction, which is electronically compensated for its ambient temperature. Heating the sensing junction generates a thermoelectric potential (emf ) proportional to the temperature difference between the two junctions. This millivolt-level emf, when compensated for the known temperature of the reference junction, indicates the temperature at the sensing tip. Thermocouples are simple and familiar. Designing them into systems, however, is complicated by the need for special extension wires and reference junction compensation. Thermocouple advantages include:
\u2022 Extremely high temperature capability: Thermocouples with precious metal junctions may be rated as high as 1800\u00b0C (3272\u00b0F).
\u2022 Ruggedness: The inherent simplicity of thermocouples makes them resistant to shock and vibration.
\u2022 Small size\/fast response: A fine-wire thermocouple junction takes up little space and has low mass, making it suitable for point sensing and fast response. Note, however, that many Minco RTDs have time constraints faster than equivalent thermocouples.<\/p>

Thermistors<\/span><\/h5>

A thermistor is a resistive device composed of metal oxides formed into a bead and encapsulated in epoxy or glass. A typical thermistor shows a large negative temperature coefficient. Resistance drops dramatically and non-linearly with temperature. Sensitivity is many times that of RTDs but useful temperature range is limited. Some manufacturers offer thermistors with positive coefficients. Linearized models are also available.<\/p>

There are wide variations of performance and price between thermistors from different sources. Typical benefits are:
\u2022 Low sensor cost: Basic thermistors are quite inexpensive. However, models with tighter interchangeability or extended temperature ranges often cost more than RTDs.
\u2022 High sensitivity: A thermistor may change resistance by tens of ohms per degree temperature change, versus a fraction of an ohm for RTDs.
\u2022 Point sensing: A thermistor bead can be made the size of a pin head for small area sensing.<\/p><\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t

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Your Sensors & Instruments Solutions Guide<\/h4>\n

How to Get Started<\/span><\/h5>\n

1. Understand and define your application requirements<\/p>\n

Many factors should be a part of the sensor system design process. The factors listed below can help you define the sensing requirements for your application. Define the typical and extremes of these environmental conditions:
\u2022 minimum and maximum temperatures
\u2022 pressure
\u2022 humidity
\u2022 shock
\u2022 vibration
\u2022 flow rate<\/p>\n

Also ask:
\u2022 What is the sensed medium (a surface or immersed in solid, liquid or gas)?
\u2022 Is the medium chemically reactive (corrosive) or hazardous (explosive)?
\u2022 Is there high electromagnetic interference potential from power switching, rectification, or radio waves?<\/p>\n

Finally, define the significance of these performance specifications in your application:
\u2022 sensing accuracy at a calibration point and\/or over a temperature span
\u2022 repeatability
\u2022 stability
\u2022 sensor time constant
\u2022 insulation resistance<\/p>\n

2. Determine which sensing technology options meet your requirements<\/p>\n

Several potential sensing technologies may meet the essential environmental and performance specifications of your application. This section of the Sensors and Instruments Solutions Guide will provide you with a basic understanding of Minco\u2019s sensing and instrumentation technology. For more information go to Sense.<\/p>\n

3. Compare sensor construction alternatives for best fit and ease of use<\/p>\n

While a sensing technology may appear to be capable of meeting the requirements of your application, the actual sensor packaging and construction must be evaluated in order to select the optimal cost\/performance balance from the available technology options. Regardless of which sensing technology you consider, the packaging of the sensor introduces some level of specification compromise in terms of cost, performance or durability. Use this guide to compare Minco\u2019s various sensor constructions and instrumentation solutions to find the best fit for your application.<\/p>\n

4. Obtain parts for testing as prototypes in your application<\/p>\n

Minco has a wide selection of standard sensor components that can often be used for prototype testing and production systems. We would appreciate the opportunity to discuss your application with you. We can help ensure that the right sensor construction is selected for your application as well as any accessory components. Often times, we are able to offer recommendations for customization to improve performance and\/or lower installed cost. Order sensors and instruments easily from our estore<\/a>.  <\/p><\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t

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Minco has established a variety of baseline specifications for standard products. This may include time response, vibration, shock, insulation resistance, dielectric strength, temperature range, pressure rating, stability, repeatability, and many more.\u00a0\u00a0<\/p>

Review the Sensors and Instruments Solution Guide to identify the specs for specific products.\u00a0\u00a0<\/p>

NOTE:<\/strong>\u00a0Specifications not found in the solution guide or on the specification drawing do not exist.<\/em><\/p><\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t

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In the world of RTDs (Resistance Temperature Detectors), platinum has gained enormous popularity. This is due to the physical characteristics that make it superior to other materials for sensing temperature.<\/p>\n

To provide interchangeability between manufacturers for the sake of global industry, there are some international standards that have been adopted by most countries:<\/p>\n