An Industrial "Thermal Imager" head with a difference

[Fraser]

Thermal imaging ...... thermal cameras..... and now for something completely different.....

Many who read the words "thermal imaging" will understandably think of thermal cameras that produce an image of the thermal scene, with varying levels of resolution depending upon capabilities of the hardware. Well this post introduces a different sort of thermal 'imager' ...... the Raytek (FLUKE) RAYMMLTSSF2V stand-off thermometer with video output !

OK, so lets talk about these thermal sensors used in industry.

In many applications there is a need to closely monitor the temperature of surfaces or equipment as part of preventative maintenance or process monitoring. It is possible to use modern thermal cameras for such tasks but is that the most appropriate tool for the job, especially for long term monitoring in potentially hostile environments? Such environments can include explosive gases or high ambient temperatures. The answer is simple ... use the appropriate tool for the job and maintain the KISS principle where able.

So what IR thermometers are found in such applications ? Some may think IR thermometers are handheld devices or 'old tech' .... if so, think again. IR thermometers come in many forms and they range from simple to sophisticated in terms of capabilities. The simplest forms are a suitable sensor + optics head that connects to a thermocouple input on a digital thermometer. No power is needed for these passive heads. Next is the IR thermometer head that includes electronics to provide either a digital or analogue output to a logging or display device. Such IR thermometers often incorporate sophisticated Germanium optics that can not only provide an excellent thermal scene capture, but also a visible scene as well. Co-axial lens designs provide the thermal energy that the sensor requires plus a normal visible light lens assembly is incorporated to provide a telescope function for aiming the head at the target of interest. The visible light lens sits in the middle of the large germanium lens. An expensive assembly ! Where optical aiming is not appropriate or needed, laser aiming is also an option. This can involve a laser built into the co-axial lens assembly or a self contained laser alignment tool that screws onto the front of the head for aiming only and is then removed for the heads normal operation. So there you have the choice of observing the target using the human eye through a cross hair telescope or by direct observation of a laser dot on the target surface.

Now to introduce the Raytek RAYMMLTSSF2V head. This is a little different to the heads detailed above. It is a self contained IR thermometer that provides digital temperature readout on an integral LCD display and to monitoring equipment or a PC via a data link. This 'intelligent' head contains many setup options to suit the application in which it is deployed. A local navigation D pad provides access to the setup menus but the head is remote controllable as well. What makes this head a little different to the normal run-of-the-mill heads is its aiming system. The head uses a large Germanium/glass co-axial lens assembly. The central visible light lens assembly provides scene imaging to both a optical eyepiece and a digital camera within the head. Yes this measuring head contains a digital camera The option of aiming the head via a simple eyepiece with cross hairs or a video camera provides the user with many options when it comes to deployment and monitoring.
When connected to a PC, the measuring head provides the user with instant temperature, logged temperature over time in graph form and the image from the digital aiming and monitoring camera within the head.

So is the head a "Thermal Imager" ? Well it contains a visible light aiming camera that incorporates a targeting cross hair. The head is aimed at the required target and the surface temperature is measured.... so yes it is a form of thermal imaging

For those wondering, yes these industrial IR thermometers are very expensive. They are designed to be rugged and effective in their intended use. They can be far more appropriate than deploying a thermal camera in the same scenario. The large Germanium lens assembly can be just as expensive as that found in thermal cameras and can be even more complex due to the co-axial aiming optics incorporated within them.

I decided to write about these measurement heads as some applications may actually benefit from using such instead of a thermal camera. I own several Raytek and AGEMA (Raytek) industrial IR thermometer systems.

Fraser

[Fraser]

Pictures of the head

[Fraser]

Pictures of my unit with the built in video camera. It has a composite video output available on the BNC connector.

[Spirit532]

Basically, a remote thermal measurement device for situations where a(likely cheaper, imagine that) true thermal camera simply won't survive.

[Fraser]

Yes indeed. They are not true thermal cameras so the user does not see a pretty picture but the required target temperature is provided and may be plotted over time by the associated software. It was the fact that this particular head incorporates a digital visible light camera that caught my eye. You could theoretically mount the head on a pan tilt unit and navigate it via the camera image and cross hairs. Sadly the size of the measured area is far larger than that of a decent thermal camera.

The lens is an interesting design ad well. The use of co-axial optics must really increase production costs and optics complexity. This us the level of care taken with the design of these heads though. An offset aiming telescope or external video camera could have been used, but the design goes the extra mile and incorporates all optics into one assembly for maximum accuracy of aiming.

In another recent thread we saw a military thermal target detection add-on for a tanks night vision system. I suspect it is not that different in principal to these units.

For high ambient temperature environments there is a heavy duty cooled housing and air purge collars are employed in front of the lens to keep it cool. These heads have a very good reliability record and are still current technology in the oil industry etc.

Fraser

[Fraser]

Some more pictures that may be of interest......

[Vipitis]

this isn't giantly different then. I was hoping for analog LWIR photography using thermal film or something...

[Fraser]

Sorry to disappoint