Products Understanding the thermal loop
Heat treatment processes are a crucial component of many manufacturing processes, but precise control of temperature requires more than just heating control. This is where the thermal loop comes into play. Thermal loop solutions have become increasingly popular for achieving improved temperature control and consistent outcomes, but what exactly does the thermal loop mean? In this article, Andy Selvy, chief system designer at industrial technology company Watlow, offers his insight.
A thermal loop is a system designed to precisely control the temperature of an object, fluid or gas. It comprises a closed loop system with vital components, such as an electrical power supply, power controller, heating element, temperature sensor and process controller. The electrical power supply furnishes the necessary energy for heating, while the power controller modulates the power output to the heating element. Subsequently, the heating element raises the material's temperature, and the temperature sensor gauges the temperature. Ultimately, the process controller fine-tunes the power output to sustain the desired temperature for the specified duration, ensuring improved temperature control and consistent results. In some cases, a single component can play multiple roles.
For example, with high temperature coefficient of resistance (TCR) materials, it’s possible for a single component to act as both a heater and a sensor, which cuts down on the total number of components and wires needed in the system. Altogether, these parts create a system known as a thermal loop that can maintain process temperatures automatically through time.
How does it work?
A home thermostat is a simple, everyday example of closed loop temperature control. You can adjust the temperature of the range, but this must be done manually. The system does not detect temperature or adjust itself — it only provides heat. A homeowner could set a thermostat and leave it for months, never having to actively direct or control the system, but the system would maintain the same temperature range during that time. They work well for heating our homes, but certainly come with limitations with regards to temperature control.
The limitations seen with traditional thermostats provide a good parallel for understanding the challenges that industries face when it comes to process heating and thermal control. For instance, heaters are typically controlled by consistently monitoring the power being provided. If power can be controlled in a more precise manner, then heaters can be better controlled and heater life can be extended. This often requires going beyond simple “power on or off” switches and introducing advanced forms of power control. Temperature sensing needs to be done in multiple zones, not just one place. For example, a surface for creating semiconductor chips might need to be divided into several zones so that temperature uniformity can be achieved at each point — much like having a thermostat in every room of your house.
Systems thinking versus component thinking
This is why systems thinking is so important. Even if you find that “best” component — the best heating element, the best sensor, the best power controller — it does not mean that you have found the best component for that particular application and system. Problems often arise not necessarily because of an issue with the right component, but rather the way the entire system has been engineered.
This can include temperature sensors that are either too close or not close enough to the heating elements, which create an unreliable picture of the temperature on a heater surface or within a heated space. Small fluctuations in temperature at the heating surface can lead to “hot spots” which, over time, can cause scorched material accumulations that can foul up the equipment, resulting in equipment failure. Lastly, the power needs and input to the system fluctuate over time, leading to inconsistent heating even when sensors are recording the correct temperature.
www.watlow.com/news 40 April 2024
www.electronicsworld.co.uk
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Highly Versatile IP67 NTC Temperature Sensor ATC Semitec stock a range of single-insulated, fully encapsulated sensors offering IP67 waterproof protection. The small bead sensor tip is moulded directly onto the cable ensuring the interface is completely sealed. The Semitec AT-11 is a versatile sensor with its small sensor tip offering accurate temperature control (with an accuracy of +/-0.3°C at 25°C) and monitoring from -50°C to +110°C. At just 5mm x 6mm x 15mm long, the sensing tip ensures a fast response to thermal change. The 600mm flexible leads enable easy installation and the AT-11 offers industry standard resistance values such as the 10kΩ/B3435K (103AT-11). Simply, ATC Semitec’s AT-11 temperature sensor, offers the best accuracy/cost/ quality ratio available in the industry. Highly versatile, they are widely used by many industries worldwide, across a wide range of diverse applications including battery management systems within e-vehicles, HVAC, air conditioning, and digital thermostats.
www.atcsemitec.co.uk
New compact PLC with satelite displays MMS Electronics Ltd introduced new compact PLC control units from DISPLAY VISIONS. These innovative controllers are designed to be particularly communicative, with a central control unit and can address up to 50 remote satellite displays. This makes these PLCs ideal for a wide range of AV, home and industrial applications, where it is important to be able to visualize process data, enter parameter data, and control the system from multiple locations. The central control unit, “PLC-Core”, is simple to use and shows measurement and process data on a brilliant 2.8 inch IPS display with a PCAP touch panel. The PLC-Core is networked with the
satellite displays automatically via Ethernet, RS-485 or Wi-Fi. The measurement values and parameters are updated automatically.
The PLC-Core EA PLC028-D8I4R4 has 8 digital inputs, 4 analogue inputs (0-10V or 4-20mA) and 4 relay outputs, Wi-Fi, RS-485 and Ethernet. Including Real-Time- Clock. Supply 12-24V. The PLC-Core is designed for top-hat rail mounting.
www.mmselectronics.co.uk
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