![]() ![]() ![]() This section of the Sensors and Instruments Solutions Guide will provide you with a basic understanding of Minco’s sensing and instrumentation technology. Several potential sensing technologies may meet the essential environmental and performance specifications of your application. Determine which sensing technology options meet your requirements sensing accuracy at a calibration point and/or over a temperature spanĢ.Is there high electromagnetic interference potential from power switching, rectification, or radio waves?įinally, define the significance of these performance specifications in your application:.Is the medium chemically reactive (corrosive) or hazardous (explosive)?.What is the sensed medium (a surface or immersed in solid, liquid or gas)?.Define the typical and extremes of these environmental conditions: The factors listed below can help you define the sensing requirements for your application. Many factors should be a part of the sensor system design process. Understand and define your application requirements Your Sensors & Instruments Solutions Guide How to Get Startedġ. Point sensing: A thermistor bead can be made the size of a pin head for small area sensing.High sensitivity: A thermistor may change resistance by tens of ohms per degree temperature change, versus a fraction of an ohm for RTDs.However, models with tighter interchangeability or extended temperature ranges often cost more than RTDs. Low sensor cost: Basic thermistors are quite inexpensive.There are wide variations of performance and price between thermistors from different sources. Some manufacturers offer thermistors with positive coefficients. Sensitivity is many times that of RTDs but useful temperature range is limited. Resistance drops dramatically and non-linearly with temperature. A typical thermistor shows a large negative temperature coefficient. ThermistorsĪ thermistor is a resistive device composed of metal oxides formed into a bead and encapsulated in epoxy or glass. Note, however, that many Minco RTDs have time constraints faster than equivalent thermocouples. 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. ![]() Ruggedness: The inherent simplicity of thermocouples makes them resistant to shock and vibration.Extremely high temperature capability: Thermocouples with precious metal junctions may be rated as high as 1800☌ (3272☏).Designing them into systems, however, is complicated by the need for special extension wires and reference junction compensation. This millivolt-level emf, when compensated for the known temperature of the reference junction, indicates the temperature at the sensing tip. Heating the sensing junction generates a thermoelectric potential (emf ) proportional to the temperature difference between the two junctions. 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. ThermocouplesĪ thermocouple consists of two wires of dissimilar metals welded together into a junction. Standardization: Manufacturers offer RTDs to industry standard curves, most commonly 100 Ω platinum to EN60751 (Minco element code PD or PE).Low system cost: RTDs use ordinary copper extension leads and require no cold junction compensation.RTD non-linearities can be corrected through proper design of resistive bridge networks. Linearity: Platinum and copper RTDs produce a more linear response than thermocouples or thermistors.Sensitivity: The voltage drop across an RTD provides a much larger output than a thermocouple.Ordinary industrial RTDs typically drift less than 0.1☌/year. 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☌.Temperature range: Minco models cover temperatures from -260 to 650☌ (-436 to 1202☏).RTDs exhibit excellent accuracy over a wide temperature range and represent the fastest growing segment among industrial temperature sensors. The element’s resistance increases with temperature in a known and repeatable manner. An RTD sensing element consists of a wire coil or deposited film of pure metal. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |