II-VI Marlow

Detectors and Sensors with Multistage Thermoelectric Coolers

This entry was posted in thermoelectric coolers and sensors on July 08, 2016 by II-VI Marlow Industries

Have you seen some of the incredible views of our universe, asteroids, comets, planets and stars? Are you familiar with the search for cures of deadly diseases and the need for a cleaner environment? What you may not know is that these things are related to thermoelectric devices.

Multistage Thermoelectric Coolers can achieve larger temperature differentials in sensors

Multistage thermoelectric coolers are used in many applications to cool detectors and sensors. These detectors and sensors are used in cameras, telescopes, microscopes and other instruments to provide scientific information about Earth and outer space. This information helps with understanding the universe and working to discover cures for diseases.

Multistage thermoelectric coolers are used to achieve larger temperature differentials, usually beyond 70 °C. Larger temperature differentials are required to achieve improved signal to noise ratio for a view in specific wavelengths. Multistage cooler applications will have small heat loads, ranging from 10’s-100’s of milliwatts, operating in vacuum packages with temperature differentials from 80 to 130 °C.

Let’s take a look at a standard multistage product, SP2394. This 4 stage device, shown below, will achieve a temperature differential of 120 °C with 500 milliwatts heat load with TEC input power of approximately 18 watts (@ 3 amps). Note, this is a vacuum environment at 50 °C hot side. See the data sheet on our website (www.marlow.com) for more information.

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Graph showing heat load & temperature differential w input power to TEC

 

The total heat load to be removed should include active and parasitic loads (convection, conduction & radiation) for the application. The hot side resistance to sink/ambient is not included in the graphs and should be accounted for when selecting the appropriate cooler and number of stages.

Some of the ambient, or sink temperatures, will be near room temperature (25-27°C). As the hot side ambient, or sink temperature, decreases, input power to the TEC (thermoelectric cooler) increases for the same temperature differential. II-VI Marlow offers materials, such as the SP2394, that operate more efficiently than standard materials at colder temperatures (below 0 °C).
As a general guideline:

Temperature Differential Stage Implementation
 ≥ 80°C 2 stages
≥ 95 °C 3 stages
≥ 110 °C 4 stages
≥ 120 °C 5 stages

*This does not include heat load estimates and may affect the number of stages.

II-VI Marlow has more than 40+ years of experience developing customized solutions to meet all specifications. Whether you’re exploring outer space, working to develop the next cure for cancer or finding sustainable energy solutions, let us partner with you to help reach your goal. For specific information, contatact II-VI Marlow and we will assist with the application and cooler selection.

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