Pushing Extremes with our RS1xx RTD Sensor

Thu, 03/25/2021 - 10:42

For Extreme Temperatures, a Solution in the IoT

The Internet of Things isn’t built on a one-size-fits-all approach: Every challenge is unique, and problems demand solutions that maximize the potential to gather data, gain insight into processes, and solve problems.

Our Sentrius™ RS1xx sensors are designed to provide a rugged, reliable, easy-to-install sensor solution for temperature, relative humidity, and open/closed status updates. They’re battery powered to run for potentially years on a single set of batteries, send data over long distances wirelessly via LoRaWAN, and are easily configurable over our Android/iOS Smartphone apps.

Once we understood our customers need for a sensor that could measure temperatures inside a room or refrigeration unit (for example) while the sensor body remained mounted on the exterior, we expanded the RS1xx product line with an external temperature probe variant. The sensor is mounted outside the measurement area, and the wired temperature probe is fitted through the exterior to measure the temperature inside. This allows the sensor to be accessed by technicians and protected from extremes, such as the cold of an industrial refrigerator or freezer.

Now once again we’ve expanded our line of RS1xx external sensor options to include more extreme temperature requirements with our line of RTD temperature probe cable assemblies. RTD sensors offer more stability, more accuracy, and better operation in extreme environments driven by our customers’ unique demands.

What’s an RTD Sensor?

Our expanded line of RTD temperature probes are designed with extreme heat and cold in mind, and to take advantage of the strengths of an RTD sensor. RTD sensors operate via a different mechanism than traditional thermocouple sensors, and they have characteristics that make them well suited for industrial applications.

In most temperature-sensing applications, the sensor is a thermocouple. Thermocouples are popular for many reasons: they’re self-powered (and therefore don’t require a constant current), they’re low in cost, and they have relatively fast measurement speed. But while they’re more common and suitable for a wide variety of applications, they may often lack in precision and they can introduce difficulties in measurement over longer control cables.

There are many other mechanisms of temperature measurement, including RTD sensors, which operate differently. RTD stands for Resistance Temperature Detector. When metals change temperature, their electromagnetic resistance changes in proportion to that temperature changes. Importantly, that relationship between temperature and resistance is very precisely measurable and very repeatable, which means a sensor can be very accurate over time and with many heating / cooling cycles.

A small current is applied to the RTD probe and the resistance measurement of that current through the device provides highly accurate temperature measurements. In applications where accuracy is critical and temperatures are at the extremes, RTD sensors can accomplish reliability that is more difficult for a traditional thermocouple.

Key Differences Between Temperature Sensors

As mentioned, there are many different technologies used commonly in temperature-sensing applications. These all operate on different technological and electronic principles, use different materials, have different levels of effectiveness, and other pros and cons for each. The following is a summary of the sensor types most common to industrial applications.

 

Sensor Type

Thermocouples 

RTDs

Thermistors

Mechanism

Voltage produced by differing temperature between metals

Change in resistance at specific temperatures in metal

Like an RTD except ceramic / polymer material

Temp Range (typical)

-200 to 1450°C

-250 to 850°C

-40 to 125°C

Accuracy (typical)

±2°C

±1°C

±1°C

Long-term stability @ 100C

Variable

0.05°C/year

0.2°C/year

Cost

Low

High

Low to moderate

Pro's

- Wide Temp Range
- Self-powered
- No Self-heating
- Rugged

- Accuracy
- Stability
- Linearity

- Sensitivity
- Accuracy
- Cost
- Rugged
- Hermetic Seal
- Surface mount

Cons

- Must compensate for cold junction
- Accuracy
- Stability
- TC extension leads

- Lead resistance error
- Response time
- Vibration resistance
- Size

- Non-linearity
- Self-heating (influences results)
- Narrow ranges

Use cases

- Vibration-resistant applications
- Applications where many sensors are needed (lower cost)

- Very high temperature (>650˚C)
- Rapid-response temperature polling

- High-accuracy and high-temp applications
- Environments with a high amount of electrical noise
- Harsh environmental conditions

- Most sensitivity below 150˚C 
- Lowest cost for high-sensitivity needs below 150˚C

 

Our RTD temperature probe cable assemblies are custom-engineered to specifications which solve our customers’ challenges. They incorporate a Stainless Steel probe, manufactured with SUS316 grade SS, which houses a Class A PT100 RTDs, meaning they’re capable of tighter temperature accuracy tolerances than other RTDs at more extreme temperatures. Built with platinum for the most consistent and linear measurement over temperature change, wide temperature range, and most reliability over temperature cycles. They offer the consistency and accuracy required by our customers’ demanding industrial challenges.

 

Our Offerings: Low and High Temp Offerings for Any Design

Laird Connectivity is now offering three RTD temperature probe assemblies (ordered separately to the enclosure) for use with the Sentrius RS1xx sensors:

  • Low Temp RTD Probe (-100°C to +100°C)
    455-00124 / 455-00124B
    Low-range temperature probe, suited for cold-chain applications such as food safety, vaccine storage, industrial cooling, and more.
  • Mid Temp RTD Probe (-40°C to +180°C)
    455-00112 / 455-00112B
    Mid-range temperature probe, suited for applications such as industrial cookers and smokers, food safety, HVAC, and more.
  • COMING SOON: High Temp RTD Probe (-50°C to +450°C)
    455-00123 / 455-00123B
    High-range temperature probe suited for applications such as extreme industrial applications, fryers, pizza ovens, and more.

Our RTD probes are engineered to support unique applications within their specified temperature ranges.

  • Food & Beverage
    The precision and accuracy of our RTD temperature probes are perfect for clean-in-place (CIP) systems used in food and beverage safety. Tanks, lines, and internal surfaces are cleaned using rapidly-moving hot water throughout a system without disassembly, and an RTD probe is perfect for verifying sanitation temperatures in these systems. They’re common in applications such as dairy processing and brewing. Additionally, an RTD is perfect for the interior of industrial refrigerators and freezers, where temperature on the interior can be monitored by an exterior-mounted sensor unit.
  • Medical
    Precise temperature monitoring is important in the storage and transportation of medical supplies, such as vaccines. Recent requirements in the ultra-low temperature maintenance of coronavirus vaccines made by Pfizer (-70°C) and Moderna (-20°C) mean precise monitoring is crucial in providing viable vaccination. Other medicines and materials also require careful temperature maintenance to remain viable and unspoiled, and our RTD temperature probes give medical providers confidence that safe temperatures ensure better patient outcomes.
  • Industrial
    Industrial applications often lead to extreme requirements in rugged construction, extreme temperature, and environmental conditions. Our RTD probes are resilient to challenging conditions, such as those in HVAC, industrial boilers, heat exchangers, and more. Using SUS316 grade SS our RTDs have good corrosion-resistant properties, beneficial for chemical processing applications where contamination and caustic materials are a factor. And in metal processing, particularly lower-temperature alloy processing like Babbitt, Bismuth, Cadmium, and others, our platinum-based RTDs provide a long-lasting temperature measurement solution that resists wear and damage.

One Size Doesn’t Fit All – Laird Connectivity Delivers the Customized

Our wide product portfolio of IoT products (sensors, gateway, antennas, and modules) are engineered with our nearly four decades of wireless design experience. And with our close relationship to customers and industry experts, our portfolio continues to evolve to support the specific and changing requirements of OEMs in the IoT.

Our RS1xx sensors are easy to install, require minimal maintenance, and support a growing range of peripheral cable assemblies that bring our customers’ designs to life.

For more on our RS1xx sensors, technical specifications, availability, and more, please visit our RS1xx LoRaWAN Sensors page.