My garage is cold, and I’m trying to cure some urethane. All it needs is a nice warm hug…
A while ago, I wrote about the need to monitor shop temperature, material temperature and mold temperature. It’s really important. These days, a go-to device for this is the laser thermometer. They’re cheap, versatile and found just about everywhere. Shops have learned a lot with these gadgets. But I’ve noticed something strange: shops use them, and some of the temperature related problems get worse. I’ve even seen this in our own lab, so what’s going on?
A quick rundown on how INFRARED THERMOMETERS do their job:
The Laser Is Cool, But…
But it has nothing to do with taking the reading. It’s a targeting guide only. These devices use a sensor to measure infrared radiation from a surface, and the laser shows you where it’s reading. More or less. Some devices point to laser to the top of the measured spot. Or the middle. Or bottom. See the problem? You might not be measuring what you think. (My pro tip: get one with two or more lasers to show the boundaries of the measured spot.)
Distance To Spot Ratio
Devices have a “distance-to-spot ratio”. The sensor is behind a lens, kinda like a single pixel digital camera. Just like a camera, the size of that what the sensor looks at depends on your distance from it. Somewhere the device will (hopefully) tell you the D/S ratio. If it’s 8:1, then you are measuring a 2″ spot only from 16″ away. That’s if you are looking at the right spot in the first place. (My pro tip: get a device with a large D:S ratio, 12:1 or more.)
These devices measure infrared energy emitted from a surface. The problem is that all surfaces emit some and reflect some. So the device is calibrated to accommodate this. Do you know what your device is set to read? Not a surprise that shiny surfaces reflect more than dull ones. With all the polished molds or liquid resin surfaces in a shop, you’re reading some of their surface energy and a good deal of their incidental reflected energy. (My pro tip: get an IR thermometer which can adjust for this. Check a commonly measured surface with a thermocouple probe and adjust the IR emmisivity setting until the displayed temperatures match.)
It’s been great to see customers get on board with measuring temps around the shop. Their new awareness they get helps them in every process. IR thermometers are a great tool for this but like any tool, they need a bit of care and concern for proper use. At Composites Canada, we’re in a lot of shops, involved in a lot of procedures.
Since we’ve seen and used so many of these tools, we’ve learned which work best for our industry. Call us any time at 905-670-7862 for some recommendations.