Laird’s Thermoelectric Coolers Optimize Machine Vision PerformanceJanuary 22, 2021 by Gary Elinoff
The new devices maintain the operating temperatures of machine vision sensors below the point where performance might otherwise deteriorate
Laird Thermal Systems’ series of high-temperature (HiTemp) ETX Thermoelectric Coolers employ the Peltier Effect to achieve active cooling for temperature sensitive machine vision applications
Image courtesy of Laird
What is Peltier Cooling?
The Peltier Effect, as described in a previous EE Power article, occurs when an electrical current passes through the junction of two dissimilar conductors. The result is a rise in temperature in one conductor, and a cooling in the other.
Devices designed to exploit the Peltier Effect do not actually absorb heat, but transfer it. The heat is transferred to the “hot” side, where it must now be dissipated. This is often achieved via a heat sink, sometimes assisted with forced air.
Machine Vision Temperature Requirements
Whatever its ultimate purpose, machine vision begins with the acquisition of very high resolution images, but performance of the CMOS and CCD imaging sensors used for the job deteriorate at temperatures above 50℃. The problem is that some machine vision applications take place in environments where the temperature reaches as high as 120℃.
Why the Necessity of Removing Heat?
As described by Laird, the problems stem from “dark current”, the electronic current that runs through photosensitive devices even when no photons are reaching the device. For every 6℃ rise in temperature, there is an approximate doubling of dark current. It follows that a 20℃ drop in temperature would reduce noise by 10dB, thereby improving the machine vision sensors dynamic range by 10dB.
The HiTemp series can create a maximum temperature differential (ΔT) of 83℃, beating out the 78℃ possible with devices based on standard thermoelectric materials.
“Our new HiTemp ETX thermoelectric cooler is assembled with advanced thermoelectric materials that boost cooling capacity by up to 10%,” said Andrew Dereka, Product Director at Laird Thermal Systems. “The robust module construction allows it to operate in high temperature environments where standard thermoelectric coolers fail.”
ETX devices must make tight, solid mechanical connections to machine vision sensors, and their compact form factors enable them to fit into tight space constraints.
The 320 watt ETX15-28-F2-5252-TA-RT-W6. Image courtesy of Laird’s datasheet
They do require mechanical mating to a heat sink or to another form of heat exchanger, as per the modus operandi of any cooler based on the Peltier Effect
Laird offers a complete guide to the 50-plus models of the HiTemp ETX series. The choices offered designers include:
- The ETX15-28-F2-5252-TA-RT-W6, a 322 watt unit sized at 52 by 56 by 3.3 mm and weighing 53.0 grams.
- The ETX3-F2-1518-TA-W6, which is a 7.7 watt device with dimensions of 15 by 18 by 3.6 mm and weighing 4.0 grams
All devices are specced for a maximum ΔT of 83.2℃.
Peltier Cooling for:
- Machine vision
- CMOS sensors
- Security cameras
- Autonomous systems
- Digital Light processors
Peltier Heating and Cooling for:
- Liquid Chromatography Systems
- Incubator Chambers
Regulatory and Environmental