{"id":75,"date":"2013-04-24T12:10:41","date_gmt":"2013-04-24T11:10:41","guid":{"rendered":"http:\/\/77.104.130.18\/~instrote\/blog\/?p=75"},"modified":"2016-09-09T12:25:11","modified_gmt":"2016-09-09T11:25:11","slug":"fluke-vt02-compared-with-a-thermal-camera","status":"publish","type":"post","link":"https:\/\/instrotech.com\/blog\/fluke-vt02-compared-with-a-thermal-camera\/","title":{"rendered":"Fluke VT02 Compared with a Thermal Camera"},"content":{"rendered":"

In January 2013, Fluke launched a brand new product, the VT02 visual IR thermometer with an infrared heat map function. Designed for the industrial maintenance market, the VT02 is a first level assessment tool, enabling you to identify potential faults that may warrant further investigation.<\/p>\n

In recent years, there has been a growing demand for thermal imaging to be carried out as part of the periodic inspection. Insurance companies may also stipulate that thermographic inspections are carried out on a regular basis as part of a fire prevention program.<\/p>\n

With the launch of the VT02 we have had many customers ask “will it do the same job as a thermal camera?”. In short the answer is no, however in order to explain this, we will look at the two products and explain what you can and can’t use the VT02 for.<\/p>\n

In order to fully explain the differences between these products, we first need to look at some basics in regard to thermal cameras and IR thermometers.<\/p>\n

What is an IR thermometer?<\/b><\/p>\n

An IR thermometer uses an Infrared sensor to detect temperature. The spot size of the temperature reading increases the further you are from the target, therefore getting an accurate spot temperature measurement can be difficult. Some IR thermometers are equipped with a laser pointer to help pinpoint the area that requires measurement and it is a common misconception that the temperature reading on the thermometer is the exact point where the laser spot is.<\/p>\n

\"1\"
\n\"\"<\/center>Distance is indicated in mm, temperature is averaged over spot diameter.<\/p>\n

 <\/p>\n

What is a thermal camera?<\/b><\/p>\n

A thermal camera is a specialist piece of equipment that has an infrared detector. Infrared radiation is emitted from all objects and the thermal camera detects the radiation and uses software to translate this into a visual image on screen.<\/p>\n


\n\"2\"\"\"<\/center>What is a thermal image?<\/b><\/p>\n

A thermal image is the visual representation of radiation emitted in a given scene. Thermal gradients in the image can be analysed to determine the location of a fault, the possible type of fault and the extent of any possible damage.<\/p>\n

In contrast to the IR thermometer, a thermal image will allow you to get a temperature reading for each pixel of the image, this ensures more accurate results and better diagnostic capability, enabling you to make further recommendations in regard to scheduled maintenance, repair works or replacement of components.<\/p>\n

So, now we have established the difference between the two products, we can look at what you can and can\u00e2\u20ac\u2122t see with the VT02 and whether or not you should consider using a thermal imaging camera as opposed to an IR thermometer.<\/p>\n

Case Study: Fluke VT02 Compared with a Thermal Camera<\/b><\/p>\n

For this test we used a demonstration board rigged with a loose connection. We then compared the resulting images and readings to that of a thermal imaging camera in order to show what the differences are.<\/p>\n

The camera settings were left at the default in order to also match that of the VT02.<\/p>\n

Emissivity:<\/b> \u00a00.95<\/p>\n

Reflected Temperature:<\/b>\u00a020.0\u00b0C<\/p>\n

Inspection of consumer unit using the Fluke VT02, first test carried out at 1 metre distance<\/b><\/p>\n

\"3\"
\n\"\"<\/center>The example here shows the IR heat map of the VT02 in use. At this distance the digital image is clear enough to see detail such as cables and switches etc.<\/p>\n

With the IR heat map you can also see there appears to be an issue in the area where the two small black cables are connected, however at this distance it is impossible to tell which of the cables has the problem.<\/p>\n

Inspection of consumer unit using the Fluke VT02, second test carried out at 10cm distance<\/b><\/p>\n


\n\"4\"\"\"<\/center>Upon closer inspection, the problem becomes clearer, however the overlay of the heat map on the digital image is not as well lined up, making it more difficult to pinpoint the hottest area and therefore the location of the fault.<\/p>\n

Note also the spot temperature of the cable as given by the IR thermometer. We will use this information later when we compare this with the image from a thermal camera.<\/p>\n

Inspection of consumer unit using a 140 x 140 pixel thermal imaging camera, first test carried out at 1 metre distance<\/b><\/p>\n

\"5\"\"\"<\/center>With this thermal image we can clearly see the problem, but the extra resolution of the thermal camera also enables us to tell which cable is affected, even at this distance.<\/p>\n

Note the spot temperature size reading at this distance, we will look at target spot sizes a little later.<\/p>\n

Inspection of consumer unit using a 140 x 140 pixel thermal imaging camera, second test carried out at 0.6m distance<\/b><\/p>\n

\"6\"
\n\"\"<\/center>The distance increase, when compared to the second test with the VT02, is due to the camera having a minimum focus distance. An out of focus image will render incorrect results.<\/p>\n

As we get closer to the cable, we can see the exact location of the hottest part, the image also shows a thermal gradient – the cable is hotter at the top.<\/p>\n

This thermal gradient is indicative of a loose connection.
\nAgain, note carefully the spot temperature we have with this image, at 58.5\u00b0C this is almost 30\u00b0C higher than the apparent spot temperature given by the VT02.<\/p>\n

Inspection of consumer unit using a 640 x 480 pixel thermal imaging camera, test carried out at 10cm distance<\/b><\/p>\n

\"7\"
\n\"\"<\/center>We have used a high end resolution camera in order to give a better point of reference for this test.<\/p>\n

With a camera of this resolution you can clearly see a lot more detail, easily pinpoint the fault but in addition, because of the greater number of pixels, you get a much more accurate spot temperature reading – here you can see the cable temperature is showing 59.1\u00b0C.<\/p>\n

Why are the temperature readings so different?<\/b><\/p>\n

Looking back at the three images captured there are three different temperature readings given for the same part of the cable:<\/p>\n

Fluke VT02 Visual IR Thermometer:<\/b>\u00a028.4\u00b0C<\/p>\n

140 x 140 pixel thermal camera:<\/b>\u00a058.5\u00b0C<\/p>\n

640 x 480 pixel thermal camera:<\/b>\u00a059.1\u00b0C<\/p>\n

You may be wondering why these readings are so different. The answer is down to the resolution of the IR detector and the size of the measurement spot. Remember our diagram of the IR thermometer, which showed a spot size ratio over a given distance? Well, the temperature reading of the target spot is an average of the overall number of pixels within the spot size, so with the thermal cameras, the more pixels you have, the smaller the spot and therefore the more accurate the temperature reading.<\/p>\n

The rule of thumb in order to get an accurate temperature reading is that the object must fill the temperature spot. With the VT02 it is not clear what the actual spot size is, as this will vary with distance. A thermal camera does not have this problem however, as the spot size is fixed, dependent upon the number of pixels, and therefore you can clearly see whether your target is filling the spot or not.<\/p>\n

To demonstrate the difference with what both products are measuring, we have an image below which shows the target spot of the thermal camera, indicating 59.1\u00c2\u00b0C, and we have then drawn a circle area onto the image with an average reading of 28.4\u00c2\u00b0C as obtained by the VT02 (remember the temperature reading is an average of the number of pixels within the target spot, typically 9 pixels for a thermal camera). This example will show you the difference in the estimated area the VT02 is measuring, compared to what you see with a thermal camera.<\/p>\n

\"8\"
\n\"\"<\/center>Surely the VT02 would still have enabled me to locate the fault, so why would I need a thermal camera?<\/b><\/p>\n

On the one hand this is true, the VT02 has highlighted an area that appeared to be an anomaly. Upon visual inspection, the operator would have noticed the loose connection and been able to fix the problem quickly, however there are additional factors that should be considered in this scenario.<\/p>\n

When carrying out analysis of a thermal image in this situation, you would apply temperature values in order to make recommendations for repair or replacement of parts.<\/p>\n

Consider the temperature readings we got from the thermal camera. When using the spot tool, we can see the temperature at this point is 59.1\u00c2\u00b0C, however the circle area gives us a maximum temperature reading of 64.1\u00c2\u00b0C, this represents the hottest part of the cable. At this level we are getting close to the cables maximum operating temperature of 70.0\u00c2\u00b0C. If the cable had been running at over 70.0\u00c2\u00b0C for a long period of time, the insulation could be compromised and this may not be visible to the naked eye, in this case along with fixing the loose connection, you should also replace the cable. In this example, even though the cable has not been running above the maximum operating temperature, it may be worth replacing the cable as a matter of course.<\/p>\n

It is also worth noting here that the analysis software supplied with thermal cameras gives you more tools to be able to add temperature readings. Remember a thermal image gives you a temperature reading for each pixel, so whereas the target spot takes an average of 9 pixels, you can use an area box to obtain the maximum temperature in a given area for increased accuracy. This form of analysis is not available when using the VT02.<\/p>\n

So, whilst the VT02 would allow you to spot the initial cause of the fault, the low temperature reading would cause you to miss a potentially dangerous second fault.<\/p>\n

So what is the purpose of the VT02?<\/b><\/p>\n

This product is better than using a standard IR thermometer, as the heat map will highlight areas that would need further investigation and possible further analysis with other test equipment or a thermal camera.<\/p>\n

It is a useful tool to use for quick location of potential problems that would normally be missed, but it should not be used for carrying out a thermal survey. Simple problems, such as overloaded circuits, could be easily located as they would show up warmer and this could then be verified with a clamp meter.<\/p>\n

It can also be used by heating engineers for locating blockages in radiators, or verifying a power flush has worked correctly.<\/p>\n

Conclusion<\/b><\/p>\n

To sum up, you will need to decide whether your application requires a thermal camera, or whether the VT02 will suffice. Whilst this article has only given a basic comparison based on one scenario, there are many factors that you should consider, both in regard to the equipment you are using and how you carry out the survey.<\/p>\n

We offer a one day training courses in thermography for electrical applications. If you are interested in learning more about this subject, please see the details of the course on our website.<\/p>\n

In addition, you can also obtain a free guide to industrial thermography here<\/a>, this handy book covers the most common applications and offers advice in carrying out a thermographic inspection.<\/p>\n","protected":false},"excerpt":{"rendered":"

With the launch of the Fluke VT02 we have had many customers ask “will it do the same job as a thermal camera?”\u009d In short the answer is no, however in order to explain this, we will look at the two products and explain what you can and can’t use the VT02 for.<\/p>\n","protected":false},"author":3,"featured_media":197,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_et_pb_use_builder":"","_et_pb_old_content":"","_et_gb_content_width":"","jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"twitterCardType":"","cardImageID":0,"cardImage":"","cardTitle":"","cardDesc":"","cardImageAlt":"","cardPlayer":"","cardPlayerWidth":0,"cardPlayerHeight":0,"cardPlayerStream":"","cardPlayerCodec":"","_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[4],"tags":[],"class_list":["post-75","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-thermography"],"aioseo_notices":[],"jetpack_featured_media_url":"https:\/\/instrotech.com\/blog\/wp-content\/uploads\/2016\/09\/IR_0007_header.jpg","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p7Siyi-1d","amp_enabled":true,"_links":{"self":[{"href":"https:\/\/instrotech.com\/blog\/wp-json\/wp\/v2\/posts\/75","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/instrotech.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/instrotech.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/instrotech.com\/blog\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/instrotech.com\/blog\/wp-json\/wp\/v2\/comments?post=75"}],"version-history":[{"count":2,"href":"https:\/\/instrotech.com\/blog\/wp-json\/wp\/v2\/posts\/75\/revisions"}],"predecessor-version":[{"id":206,"href":"https:\/\/instrotech.com\/blog\/wp-json\/wp\/v2\/posts\/75\/revisions\/206"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/instrotech.com\/blog\/wp-json\/wp\/v2\/media\/197"}],"wp:attachment":[{"href":"https:\/\/instrotech.com\/blog\/wp-json\/wp\/v2\/media?parent=75"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/instrotech.com\/blog\/wp-json\/wp\/v2\/categories?post=75"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/instrotech.com\/blog\/wp-json\/wp\/v2\/tags?post=75"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}