Resistance Temperature Detector Sensors
December 31, 2008 by Editor
Filed under Temperature
St. Louis, MO – Watlow offers a full line of Resistance Temperature Detector (RTD) sensors for a wide variety of process and industrial applications. Watlow engineers can also solve difficult application problems and offer solutions tailored to meet specific application requirements.
Watlow’s RTD sensors are designed to ensure precise and repeatable measurements as well as meet environmental requirements for each application. A high signal-to-noise output increases the accuracy of data transmission and permits greater distances between the sensor and the measuring equipment. Watlow’s RTD sensors can be configured to meet specific application needs with options including element type, lead wire configuration, termination style, sheath materials, lengths and diameters, process connection heads, transmitters, thermowells, spring loading, flanges and surface mount packages.
Watlow RTDs offer a high degree of accuracy and a wide temperature operating range of -200 to 650°C (-328 to 1202°F). The linear change in resistance per degree change in temperature makes it easy to interpret the signal, allows for less complex instrumentation and requires no cold junction compensation like that found in a thermocouple.
Predictable resistance at a given temperature can be produced with Watlow’s RTDs. Resistance wire RTDs have a positive coefficient by increasing resistance with temperature increases. These sensors work in a variety of industries including processing, food equipment, plastics processing, petrochemical processing, microelectronics, and air, gas and liquid temperature measurement.
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Selco’s 1/2-Inch Disc Thermosats
December 31, 2008 by Editor
Filed under Temperature
ANAHEIM, CA – Selco Products has introduced the Precision Differential Thermostat Series for extremely accurate temperature control. Featuring tight differential between 9°F and 14°F (5°C to 8°C), these ½-inch Automatic Reset Disc Thermostats are suitable for temperature control in heaters, commercial food equipment, spas, and medical equipment.
The new Precision Differential Thermostats are available with Selco’s Open on Rise (OA) and Close on Rise (CA) configurations. Features include a Phenolic Body, setpoint between 50°F and 203°F (10°C, 95°C), and a highly reliable switch that utilizes a temperature sensitive, snap-action bimetal disc, electrically isolated from the switch. Contacts open or close on rise when surface or ambient temperature increases to the set point of the calibrated bimetal disc. The calibrated fixed disc is mounted adjacent to the monitored surface, providing a rapid response to temperature changes.
Silver contacts are rated to 15 amps at 125VAC (10 amps at 250VAC) and gold contacts are rated to 1 amp at 30VDC. Thermostats may be factory calibrated at any temperature between 50°F to 203°F (10°C to 95°C) and specified with a wide variety of mounting options and terminals. Value added services provide additional customization with soldered wire leads, connectors and epoxy overmolding. Ratings and approvals include UL, CSA, VDE and ROHS compliance.
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EZ-ZONE® RM Multi-Loop Temperature/Process Controller
December 31, 2008 by Editor
Filed under Temperature
St. Louis, MO – Watlow® introduces the EZ-ZONE® RM – a configurable multi-loop temperature/process controller. The EZ-ZONE RM is the first industrial controller to integrate an entire assembly of control loop functionality in one space-saving, DIN-rail mounted package.
EZ-ZONE RM can be used as a PID temperature/process controller, an over/under limit controller or these functions can be combined into an integrated controller. Other control functions can be integrated as well, such as high amperage power controller output, creating a complete and integrated thermal loop controller all in one package.
EZ-ZONE RM can be configured with between 1 to 16 modules controlling from 1 to 64 loops. Because the controller is single-loop scalable, customers pay only for what they need – exact loop count.
EZ-ZONE RM allows for many optional integrated controller functions to be combined together or ordered in different quantities, including:
* PID temperature/process controller;
* Over/under temperature limit control loops;
* 10 or 15 ampere power output/heater driver options;
* On-board data logging;
* Current measurement input;
* Sequencer start up and control function;
* Programmable timer and counter functions;
* Programmable math and logic options;
* Multiple communication protocol options;
* Mobile configuration with removable secure digital flash card
* SPLIT-RAIL™ configuration to isolate low voltage input modules from high voltage output modules.
This new rail mount integrated multi-loop controller is ideal for semiconductor processing, photovoltaic, packaging, plastics processing and a variety of other applications that require multi-loop control.
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Fiber-Optic, Ultra-High Temperature Sensor
December 31, 2008 by Editor
Filed under Temperature
Pine Brook, NJ - Chiral Photonics is proud to announce the newest addition to its Helica products – a robust fiber optic temperature sensor designed for the most demanding industrial and R&D applications that require stability to 1000 °C.
The sensor was designed for applications ranging from weld monitoring and control to turbine engine service and design. The sensing element is a monolithic glass fiber and is as stable as the silica glass. It is not reliant on any moving parts or coatings and the sensor packaging can be tailored to suit the application needs.
The Helica Temperature Sensor is based on Chiral Photonics’ patented chiral grating, which is fabricated by twisting, or microforming, the fiber as it is passed through a miniature heat zone to produce a distinct dip in the transmission spectrum. The spectral position of the dip in this chiral fiber changes with temperature allowing it to be used as a temperature sensor.
“Customers have been enthusiastic about this monolithic glass solution which does not rely on photoinduced gratings or coatings or moving parts, thereby offering the reliability inherent to glass,” states Dan Neugroschl, Chiral Photonics’ CEO.
Specifications:
* Temperature Range: Up to 1000°C
* Accuracy: 1%
* Sensitivity : 0.01 nm/°C (nominal)
* Probe (metal sheathing) Length: 300 mm standard – Other lengths available upon request
* Sensor/Grating Length: 15 mm – Other lengths available upon request
* Sensor Placement: 25 mm from probe tip – Other configurations available upon request
* Connector Type: FC/APC – Other connectors available upon request
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Thermocouple Data Logger from Omega
December 31, 2008 by Editor
Filed under Temperature
The OM-EL-USB-TC data logger measures and stores over 32,000 temperature readings from either type J, type K or type T thermocouple which plugs into a miniature female thermocouple receptacle at the base of the unit. The user can easily set up the initial data logging parameters including thermocouple type, logging rate, start-time, high/low alarm settings, logging mode and desired temperature units (Celsius or Fahrenheit) and also download the stored data by plugging the module straight into a PC’s USB port and running the easy-to-use Windows software.
Downloaded data can then be graphed, printed and exported to other applications such as Excel. The data logger is supplied complete with a long-life lithium battery. Data logger status is indicated by flashing red, green, and orange LEDs. This product is perfect for chemical, water, and pharmaceutical industries.
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1/16 DIN Temperature Controllers
December 31, 2008 by Editor
Filed under Temperature
The CN740 offers accurate temperature measurement and control in a 1/16 DIN package. This product accepts a variety of thermocouple and RTD inputs, and process value and set-point value can be viewed simultaneously on the large dual LED display.
Auto-tuning, engineering units (°F or °C), and alarm status are also indicated on the faceplate. This CE compliant product offers single output control, either simple ON/OFF or full PID, and two alarm outputs. This product is suitable for water, chemical, plastics, automotive, and food processing industries. Free software download is available.
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Thermocouples Take the Heat
December 31, 2008 by Editor
Filed under Temperature
Proper selection is essential to obtain the most accurate temperature measurement and control from thermocouple sensors. Use these guidelines to ensure the right sensor for the application.
Thermocouples are widely used as temperature sensors for data acquisition, instrumentation, process control, and hand-held digital thermometers. They are inexpensive, rugged, and can measure temperatures of several thousand degrees C. In fact, thermocouples and noncontact infrared pyrometers are the only devices available that can measure temperatures above 650°C. By comparison, thermocouples are significantly less expensive than infrared pyrometers and can be permanently installed.
Although thermocouples have been used for many years, their principal of operation is frequently misunderstood. The most appropriate and accurate thermocouple type that you can select for an application depends upon its basic construction and the method of installation.
K-Type thermocouples are typically used in digital multimeters and hand-held thermometers. Each connector blade is made of the same material as the thermocouple wire that connects to it.
How thermocouples work
When two wires of different metals are connected at two junctions and the measuring junction is exposed to a higher temperature than the colder reference junction, current flows in the series circuit. This phenomenon is called the Seebeck effect, discovered by T. Seebeck in 1821. When the reference junction is opened, the voltage that appears across the open ends is a function of the sensing junction temperature. Its polarity and magnitude depend on the materials used to form the thermocouple.
When two dissimilar metal wires are connected at junctions J1 and J2 and the Measuring junction J2 is exposed to higher temperature than the reference junction J1, current flows in the closed circuit. This phenomenon is called the Seebeck Effect.
Thermocouples cannot be connected to just any type of instrument terminal. For example, when a thermocouple is connected to copper input terminals of a meter, two new thermocouple junctions are created. Additional cold or reference junctions produce additional voltages in series that can add to or subtract from the voltage produced by the measuring junction and significantly reduce accuracy.
To achieve reasonable accuracy, an ice bath can be used to keep the temperature of the two additional junctions stable at 0ºC regardless of the ambient temperature. Because the two junction temperatures are constant and the same, the voltages produced by the additional junctions are also constant and can be easily compensated in the meter. However, handling ice baths are a bother and modern instruments use an electronic circuit to replace the ice bath for cold junction compensation.
Connecting thermocouple wires to copper leads or terminals of an instrument creates two additional cold junctions, J2 and J3. They produce additional voltages that vary depending on the ambient temperature of the meter. An ice bath keeps these two junctions at a stable 0° C and holds thevoltages constant, which is easy to compensate within the instrument.
Selecting thermocouple types
Different types of thermocouples use various combinations of several metals resulting in a wide range of sensitivies, linearities, temperature ranges, and corrosion resistances.
The temperature extremes and environment to which the bare thermocouple (TC) wires will be exposed are the starting points in the type selection. For example, the most commonly used J-type is recommended for reducing atmospheres and operates between -270 and 760ºC.
Another widely used general-purpose TC, type, K, has an operating temperature range of -270 to 1,372ºC, but is recommended only for clean oxidizing atmospheres. Many digital thermometers and multimeters with built-in thermometers are supplied with K-type thermocouples.
Recommended for sub-zero temperature measurements due to its moisture resistance is the T-type thermocouple that spans -270 to 400ºC. It is compatible with oxidizing and reducing atmospheres. The E-type has a range of -270 to 1,000ºC and the highest EMF output compared to other standard thermocouples. It has a high resistance to corrosion at low temperatures and can be used in oxidizing, reducing, and all inert atmospheres.
These thermocouples belong to what is called the base-metal group. They are inexpensive and widely available. A second major group of thermocouples is called the noble-metal group (platinum alloy). Noble-metal thermocouples are more expensive than base-metal types and have the highest corrosion, and oxidation resistance, and temperature limits.
Accuracy varies among the different types of thermocouples. For example, the standard tolerance for J and K types is ± 0.75% or ±2.2°C. R and S types have a tolerance of ± 0.25% or ±1.5°C. The tolerance is defined as the deviation from an ideal thermocouple, not the degree of nonlinearity.
All thermocouples have different sensitivity. For example, the most sensitive E-type generates 58.5 µV/°C voltage change at 0°C. The least sensitive B-type generates only 6 µV/°C at 600°C. All thermocouples have nonlinear voltage vs. temperature curves. Thermocouples of the same type are completely interchangeable and produce measurements within the given tolerances.
To achieve a high degree of accuracy over the full temperature range, thermocouple outputs should be linearized using hardware and software techniques. Thermocouple tables published by the National Institute of Standards and Technology (NIST) should be used as a reference to accurately convert thermocouple output voltage to a temperature reading.
Response time and protection
The construction and type of insulating material surrounding the thermocouple must match the temperature range and atmospheric environment to prevent deterioration. The simplest and least protected type is the wire thermocouple, which has an exposed junction and no protective sheath. Advantages of this type are fast response, low cost, light-weight, and flexibility of use. A major disadvantage, however, is that it is susceptible to environmental and mechanical damage.
Sheath covered probes are used where the thermocouple wire must be protected. Here, the wires are embedded in ceramic insulation, with a stainless steel or nickel alloy sheath enclosing the assembly. The selection of sheath material depends on the thermocouple’s operating temperature and atmospheric environment. In addition, the ceramic insulator must survive the upper temperature limit.
Thermowells and tube assemblies made of carbon steel, stainless steel, and brass sheaths are frequently used for heavy-duty industrial and corrosive environment applications.
Sheath covered thermocouples can have an exposed, ungrounded, or grounded measuring junction. The junction selection depends on the environment and mechanical impact the junction will be subjected to. The exposed junction has the fastest response of all types, but is the least protected from the environment. Another advantage is its relatively small mass in contact with the measured object. This minimizes the heat sinking effect that could temporarily lower the temperature of a small object during the test.
Thermocouples with exposed junctions are not usually isolated electrically from the metering circuit. If the thermometer shares a common lead or electrical potential with the circuit being measured, touching a live circuit with the exposed thermocouple can create a short.
The exposed thermocouple junction has the fastest time response, but it is susceptible to mechanical damage and corrosion. Totally enclosed ungrounded and grounded thermocouple junctions are well protected from the environment, but they have slower response times than the exposed junction.
The grounded thermocouple junction also can be a potential safety hazard. The thermocouple and insulator are completely sealed and protected from the atmosphere, but the junction is welded to the sheath from the inside. It provides a path for a ground return circuit through the sheath, which can be a shock hazard. This type provides a faster thermal response than the ungrounded type, but it is much slower than the exposed type with the same sheath diameter.
The ungrounded junction has the best thermocouple protection of all types, including electrical isolation. However, it is also the slowest.
Scientists and engineers are developing new thermocouple sensors especially for applications such as aerospace, metal processing, petrochemical, cryogenics, and scientific research where sensors are subjected to extreme temperatures and aggressive environments. The challenge is to increase the thermocouple protection from the environment without the penalty of increasing the response time.
Another area of development is in the design of nonstandard thermocouples for very specific types of applications. Metal alloys are optimized to increase the measurement accuracy and reduce drift over time. Such sensors maintain required accuracy over longer periods of time reducing maintenance cost and equipment down time.
Welding is the preferred method of forming a measuring junction. Thermocouples make contact at a single point suitable for surface and liquid measurements. The mechanical bond is the strongest and the full-temperature range is not limited by the bond.
Thin-film thermocouples are now being used in many environmentally troublesome applications. These sensors are formed by depositing thin film strips of thermocouple metals on various base materials. Their small size, low profile, and fast response time are ideal for a broad range of surface temperature measurements. For example, thin film thermocouples are formed on metal parts inside jet engines to monitor engine temperature without causing flow perturbation. Other applications include thermopiles, temperature measurements on silicon wafers, and thermal converters.
Make your own thermocouple
Simple thermocouples can be constructed in-house by combining either bare or insulated thermocouple wires and bonding them at the measuring end. The wires can be welded, soldered, silver soldered, or twisted to make a measurement junction.
Twisting thermocouple wires is the easiest method and does not require any special tools, but it produces the least reliable connection. Since the wires are not actually bonded together, corrosion or vibration can interrupt the electrical contact over time. Twisting can also lead to acquiring erroneous temperature readings. Several turns are required to get a secure junction, so the first point where the two wires touch is a certain distance away from the point of measurement. As a result, a surface measurement reading can be different from the actual temperature because the measuring junction is not in contact with the surface. A twisted thermocouple is usually satisfactory for liquid or air measurements where the whole twisted area is submerged.
Soldering or brazing techniques limit the operating temperature range to the melting temperature of the solder. Care should be taken to make a firm mechanical connection between the thermocouple wires. If the solder holding the wires together separates the thermocouple wires from each other the junction will not be formed even though electrically the circuit will be complete.
Welding is the preferred way of assembly, but producing a good welded thermocouple tip without proper equipment is not easy. A poor weld can produce an open circuit connection. Overheating the welded connection can change the operating characteristics of the thermocouple metals. For these reasons, commercially available thermocouple junctions are bonded on special capacitive discharge welders where energy and weld temperature are closely controlled.
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Small Thermostats from Omega Engineering
December 31, 2008 by Editor
Filed under Temperature
The new KT011 series of small thermostats are compact in design and DIN rail mountable. The thermostat features a wide adjustment range and is available with a Celsius (0 – 60°) or Fahrenheit (32 – 140°) scale.
The CE compliant product is equipped with color coded temperature dials: red for normally closed models (thermostat opens at temperature rise), and blue for normally open models (thermostat closes at temperature rise).
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Temperature and relative humidity sensing instruments for accurate control.
December 31, 2008 by Editor
Filed under Temperature
Minco has a new line of temperature instrumentation. Minco transmitters, controllers, indicators and accessories are designed to work with Minco temperature sensors and heaters, but can work with a wide variety of other devices.
Temptran™ temperature transmitters amplify low-level signals from RTD or thermocouples. These transmitters are immune to electrical resistance in extension wires, so they are more accurate than other transmitters. They linearize temp signals, so they are excellent low cost signal conditioners.
Temperature controllers are available in programmable, miniature, monitor/relay or “sensorless” models. Temperature indicators are available in digital, head-mounted or current loop models. Instrumentation accessories include solid-state relays and heatsinks. A number of customized controllers are also available. These include proportional, dual power, high current and multi-channel models.
Relative humidity and humidity plus temperature transmitters have advanced microprocessors. Digital signal processing allows these transmitters to precisely match the characteristics of the humidity sensor to a wide range of RH and temperature values found in the many applications. The humidity sensor has a platinum RTD for temperature compensation. This sensor offers outstanding resistance to airborne contaminant and chemicals, and is protected by a sintered stainless steel filter to resist condensation.
With over 7,000 temperature sensor designs, let a Minco engineer help you choose a standard or customize approach to meet your temperature sensing, controlling and monitoring requirements.
A Sensors & Instruments Solutions Guide Design Guide can be ordered in print or downloaded. A Non-invasive Sensors Design Kit and a Sensor Configurator Tool are also available.
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VersaMax Micro Thermocouple Expansion Module
December 31, 2008 by Editor
Filed under Temperature
Charlottesville, VA — GE Fanuc Intelligent Platforms announced the availability of a new module for its popular VersaMax Micro controller that offer productivity and flexibility in a cost effective solution. The new VersaMax Micro Thermocouple (Type K, J, E, S, T, B or N)/Millivolt (-/+ 50mV or 100mV) Expansion module can be used in a wide range of temperature monitoring and controlling, as well as weighing applications.
As productivity demands and cost pressures increase, the VersaMax Micro and its accompanying
There are two cost effective module types available, four thermocouple inputs and two analog outputs expansion module and four thermocouple inputs and no analog outputs module. The new modules can also be used with the QuickPanel control as a low cost I/O solution.
Packaging and assembly applications requiring temperature control for sealing products, oven control, product curing, PID control, weighing product in food packaging, and process control will benefit from the quality construction and cost-conscious value.
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