Feature: T&M
Trough modelling and characterisation
of potential scenarios, followed by assessment algorithms, the outputs of smaller sensors can be compensated accordingly, without sacrificing the sensors’ stability and accuracy. Devices such as Melexis MLX90632
(Figure 2) feature active-compensation mechanisms that enable high performance in small spaces. Contained in a surface- mount QFN package (3mm x 3mm x 1mm), this compact yet accurate non-contact thermometry solution eliminates the need for bulky, metal-can FIR sensors, thereby enabling streamlined system designs. Calibrated before shipment, MLX90632
Figure 1: The three stages of DNA amplification involved in PCR analysis
direct contact thermometry method are impractical. Around 700,000 Covid-19 PCR tests are currently done daily in the UK alone; this figure was almost twice that at the height of the pandemic. Te high throughput nature of the work means that new batches of specimens need to be set up very quickly, so direct contact measurement is not appropriate here. In addition, the temperature sensors need to be calibrated accurately, which takes time and requires trained staff. Also, any contact with the sample tubes may result in other samples being contaminated. FIR sensors deliver a significant
advantage here by enabling non-contact temperature measurement. Te chance of cross-contamination between specimens is greatly reduced by avoiding the need to
touch the specimen tubes. Furthermore, if the correct devices are sourced they will be compact enough to fit into space- constrained designs.
Maintaining stability Tere is a key engineering challenge associated with migrating to FIR temperature sensors in smaller packages for portable, handheld and wearable equipment. Whilst the large metal packages in bigger systems have greater thermal mass – which improves their operational stability and mitigates the build-up of thermal gradients within their packaging, as devices get smaller they are more easily influenced by external thermal interference. Tis can come from other, nearby components.
devices deliver incremental resolution of 0.02°C over an object temperature range from -20˚C to 100˚C for the medical- grade version and -20˚C to 200˚C for the standard industrial version. The standard version measurement accuracy of ±1°C can be enhanced by selecting the medical- grade version, which has a ±0.2°C margin within the temperature range of the human body. Its inherent compactness supports the
development of portable PCR processing systems, so that analysis can be done closer to the point of care, rather than having to send specimens to a centralised lab, which clearly takes more time.
Figure 2: Melexis’ compact MLX90632 MEMS-based FIR temperature sensor
Possibilities FIR-based thermometry opens up a multitude of different application possibilities, including industrial process observation, livestock monitoring, fitness tracking and smartphone apps. Te global pandemic of the last two years has clearly highlighted its value from a healthcare perspective – in both clinical and lab environments. Rapid access to accurate temperature data is vital for biochemical processing and diagnostic purposes, so the sensor devices incorporated into equipment must be able to fully support this. Advances in sensor design and the accompanying algorithms mean that devices are now available in compact packages, making them easy to integrate into equipment whilst remaining impervious to thermal interference that could impact the quality of their data.
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