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Temperature

Minco works diligently to provide the best temperature sensing solutions available today. We build sensors from start to finish with a focus on exceptional product quality. Whether you need a custom designed sensing package or an off-the-shelf option, Minco has sensors for your application. Over the years, we have designed thousands of custom sensing packages to seamlessly operate in a wide range of applications.

Minco sensors can be found in applications in a variety of industries including medical, aerospace, power generation, rotating machinery, oil & gas, semiconductor, industrial and commercial. We have earned a reputation for having the highest quality temperature sensors and sensors built to withstand hazardous environments.

Most temperature sensor types can be made with thermocouples, thermistors, integrated circuits or resistance temperature detectors (RTDs). The RTDs most commonly utilize 100 or 1000 ohm platinum elements but can also be built using nickel, copper or nickel-iron elements. 

Our efficient sensor designs are cost-effective and easy to install to save you time and money without sacrificing accuracy and reliability.

Building Automation

You’ll find Minco temperature sensors in a variety of building automation technologies for HVAC applications.

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Element

Minco’s ceramic elements provide accurate temperature measurement over a wide temperature range and are high-shock and vibration resistant.

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Probe

Minco’s advanced probe technology and manufacturing capabilities support high quality and innovative solutions for aerospace, medical and industrial applications.

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Stator

Minco’s high quality stator RTDs are trusted by industry leaders because they provide continuous temperature protection of motor and generators as well as long-term trend data.

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Surface Sensor

Minco’s thermal ribbon sensors can be installed anywhere for fast, accurate temperature sensing and response in aerospace, medical and industrial devices.

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Designing for Accuracy

How accurate is a temperature sensor? It starts with calibration tolerance. For example, 100 Ω platinum RTDs typically have a calibration tolerance of ±0.12 Ω (±0.3°C) at 0°C.

However, there are a host of application specific characteristics that can introduce inconsistencies between the indicated temperature on a controller, and the actual temperature of your target.

Below, are some typical temperature measurement problems, and proposed solutions:

Repeatability/stability: Repeatability tells how well the sensor repeats subsequent readings at the same temperature. Stability is the absence of long term drift. In many cases, the user is less concerned with absolute accuracy than with the ability of a sensor to maintain a process at the same point once properly set.

Solution: Platinum RTDs are the most stable device for temperature measurement, such that they are used as the interpolation instrument for the international temperature scale (ITS-90) for temperatures from -260°C to 962°C. Industrial models will typically drift less than 0.1°C per year in normal use. Due to increasing demands for wider temperature ranges, higher accuracy, and longer life, platinum RTDs are becoming the de facto temperature measurement technology.

Time lag: When temperatures change rapidly, sensors may not keep up.

Solution: Minco specializes in fast response RTDs. Most models have a time constant of 2 seconds or less (in water at 3 ft/sec). Custom engineered designs can offer faster time response, while still protecting sensing elements from vibration, pressure, and other environmental risks.

Time constant is defined as the time it takes a sensor to reflect 63% of a step temperature change:

Time lag

Conduction errors: Sensor packaging and leadwires can sink heat away from the sensing element and introduce temperature error.

Conduction errors 

Solution: Internal sensor design and carefully selected materials can direct the heat transfer to the sensing element for more accurate temperature measurements, as shown above. Minco's tip-sensitive probe design is a prime example of such design. Installation (sufficient immersion or sensor embedment) is also critical for optimal heat transfer and consequent temperature accuracy.

Point sensing errors: In places where temperatures are stratified or gradients are large, the temperature at a single point may be unrepresentative or misleading.

Solution: Wire-wound and sensor arrays promote temperature detection over a larger area. This provides an average temperature within the medium. Additional details on temperature averaging can be found within each technology product group page.

Lead wire resistance: Resistance in the leads between RTDs and control points elevates apparent readings.

Solutions: Sensors with higher resistances will mitigate the influence from lead wire errors. Using 3 or 4-wire compensating circuits allow the instrumentation to factor out some or all of the lead wire resistance error. Some applications may be best to integrate with a 4-20 mA temperature transmitter to send signals over long distances. For more information on these options, check out the responses on our Frequently Asked Questions (FAQ’s) page.

Self-heating: The phenomena known as “self-heating”, is inherent in all resistive temperature devices. To measure resistance, the meter forces an electrical current (measurement current or excitation current) through the device, and measures the voltage drop across it. Using ohms law, the meter can then calculate the resistance: Resistance = Volts / Amps

However, any time a current passes through a resistance, power (in the form of heat) is created. The power (in the form of heat) affects the effective temperature of the sensing element, such that an error is introduced. The magnitude of the error is dependent on how well the power (heat) can be dissipated.

Solution: As a general rule, limit current to 5 mA for industrial applications and even lower for applications such as space. Most Minco RTDs, and especially Thermal-Ribbons, have a large surface area to dissipate heat and reduce self-heating effects. There are several factors that affect dissipation (and therefore self-heating):

  • Sensing element surface area: larger surface area will dissipate more power, so thin-films (very small surface area) have much more self-heating than wire-wound elements. In heater applications, this is similar to watt-density.
  • Environment: moving water has a far greater ability to “remove heat” than still air. Therefore, the effects of self-heating are much worse in still air than in a fluid such as moving water.
  • Resistance: from Watt’s law (Power = Amps² x Resistance), you can see that the power (heat) is directly proportional to the resistance (for a given current). Therefore, a 1000-ohm element will have 10x worse self-heating than a 100-ohm element with the same surface area and measurement current.
  • Current: from Watt’s law (Power = Amps² x Resistance), you can see that the power (heat) is directly proportional to the square of the current. Therefore, measurement current has a significant impact on self-heating. Thin-film RTDs often require 1 mA or less for 100-ohm elements, and 0.3 mA or less for 1000-ohm elements.

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