UNI-T UT303C non-contact thermometer - Page 1
Forum section: electronics / general

author: David_AVD
author_rank: Super Contributor
timestamp: October 07, 2012, 07:30:39 am
content: Has anyone here bought a UNI-T UT303C non-contact thermometer or similarly unit? If so, do you find it useful for measuring things like transistor, resistor or heatsink temperature?At present, I use a K type thermocouple but that's not always a convenient solution. Sometimes I'd like to "scan" along a few output transistors and compare temperatures.I've been wondering if the IR method would be easier for rough measurements. I thought the C version of the UT303 with it's 30:1 spot ratio would let me measure relatively small areas?

author: SeanB
author_rank: Super Contributor
timestamp: October 07, 2012, 11:09:03 am
content: IR thermometers are very good for that, a poor man's thermal camera. I use mine mostly for HVAC work, and a lot to find poor connections on switchgear, which it shows up quite well and pretty fast. Also can be used to check power draw, as it shows up the warmer cables nicely. One is a smalll one from RS, the other is a cheapie I got at the tool store. Available herehttp://www.tooltime.co.za/Products.aspx?cat=193quite cheap

author: David_AVD
author_rank: Super Contributor
timestamp: October 07, 2012, 11:40:20 am
content: Yeah, I'd love a thermal imaging camera, but that's just not in the budget I'm afraid.

author: David_AVD
author_rank: Super Contributor
timestamp: October 07, 2012, 11:49:43 am
content: The UNI-T UT303C I was looking at is 30:1 and is only $88 on eBay. The UT301B is 12:1 and about $65.$88 is still very cheap, so is the 30:1 spot ratio bad in any way? I was thinking that it would allow more precise control over the measured area.

author: Rerouter
author_rank: Super Contributor
timestamp: October 07, 2012, 11:52:56 am
content: the main thing to know about a IR thermometer is it will only measure the average of what is in its spot, so if your measuring a component make sure the spot is contained entirely on the surface you want to measure,for power electronics, e.g. a TO-220 package, you want to make sure the spot is entirely on the black body not the reflective pad,if you want one where you dont need to worry about effacacy that may be in your budget, chase up a dual wavelength one, and it will do the corrections internally, no matter the surface, so it will always be quite accurate, as a conventional one can give quite different readings between the shiny heatsink and the black plastic at the same temperature,

author: David_AVD
author_rank: Super Contributor
timestamp: October 07, 2012, 12:11:07 pm
content: I couldn't find a manual for the UNI-T model, but does anyone know if the laser spot is indicative of the measurement area?

author: Fraser
author_rank: Super Contributor
timestamp: October 07, 2012, 12:29:41 pm
content: To be clear here, you need to consider what the IR thermometer was designed for. Unless it is designed for close-in work on semiconductors like my Exergen series D unit fitted with a special 1:1 'cone' measuring head on a flexible cable, it will likely be designed for distance work in excess of 50cm. The minimum measurement spot size must be considered. My Raytek PM20 Gun style unit and the Agema Thermopoint 8000 may be very clever but they have a minimun spot size of 20mm ! Thats a bit larger than most semiconductors so it will produce an average for its view and incurr an error. I attach some brochures and the manual for my Exergen IR thermometer which may help understand the issues. Thermography can get a little complex if more than a basic accuracy is required. You have to also consider Emissivity values and possibly painting reflective components black !I have many Unit-T products but you may wish to consider cheaper alternatives as I did.Kind RegardsFraser

author: David_AVD
author_rank: Super Contributor
timestamp: October 07, 2012, 12:39:26 pm
content: OK, sounds like I need to get a hold of the manual for the UNI-T one before jumping in.

author: Fraser
author_rank: Super Contributor
timestamp: October 07, 2012, 12:44:53 pm
content: Have you considered the Fluke 80-T multimeter IR thermometer adapter ? I picked a new one up for GBP10 a while ago ! It has a very small insulated input 'tube' and looks to be ideal for component temperature measurements. Manual is attached.

author: Fraser
author_rank: Super Contributor
timestamp: October 07, 2012, 12:52:39 pm
content: For the UT-301B and UT-303C manuals try Googling the following url :http://www.cihazpazari.com/images/Pdf/UT301_302_303_Eng%20Manual.pdfThen when Google shows the URL in the hit list, use the 'Quick view' option to see the manual. The original page is no longer working but Google has a cache copy.You asked about the laser guide accuracy. These are often positioned just above the IR input aperture. Just like a telescopic sight on a rifle, it is designed to be either accurate at a set distance, or it can run parallel to the sensor reception cone. At a distance of say 600mm the small offset error will be of no consequence as it will still fall within the cone of detection. Close-in to the IR thermometer the error is more significant as the cone becomes smaller. My Thermopoint is fitted with either an optical (cross hair sight) or laser alignment option. Both work through the CENTRE of the Germanium lens for maximum accuracy and are in the centre of the detection cone. This is not done on cheaper units like the Fluke and UNI-T products due to the optics cost and the purpose for which they were designed.There are close focus versions of the Thermopoint and many other 'Process' IR monitors that are suitable for PCB tests but mine is a general purpose version.Update:Having re-read your question regarding the laser spot....if you are asking whether the laser spot size has any relationship to the measured IR spot size, then the answer is no for most, if not all, cheaper IR thermometers. I believe some Raytek and Fluke instruments may project a more complex 'target' using the laser but I can't confirm that a relationship between measurement spot and laser target image diameter actually exists.I attach pictures of the Thermopoint 8000 'through the lens' aiming optics and cross hairs.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: October 07, 2012, 01:43:50 pm
content: To provide more detail of the Actron IR thermometer and the reason I use it on components, I have attached more pictures of its 'cone' head. It is very similar to the Exergen unit that I have already detailed with a 1:1 D:S ratio but at a fraction of the cost ! The IR aperure is approximately the same diameter as a AAA battery which is excellent for small components. It is plastic coated on the outside bit the cone is metal so care is needed when touching a PCB with it. I also need to clean my units input port .... It as a tad dusty !Fraser

author: saturation
author_rank: Super Contributor
timestamp: October 07, 2012, 03:42:34 pm
content: I use IR thermometers all the time. There are limitations but they are faster than any contact thermometer. The real issue isn't if they are useful, I think its more that buying a Uni-T is worth the money. I think if you can easily return it so you can check it out, it would be worth it. I've found $10 no-name brands to work well, cheapos tend to have lower spot ratios and poor aiming, use plastic fresnel lenses than are sensitive to ambient temperature but otherwise measure nicely, my cheapos are no worse than 5C off but more typically 1C off a thermocouple measurement.

author: T4P
author_rank: Super Contributor
timestamp: October 07, 2012, 07:31:16 pm
content: I use a ultra-cheapie i got off from DX (16.99 folks ) that at least can turn the laser on and off, same for the backlight and the C/F measurement unitsSo here's a few things :12:1 ratio, 38mm @ 30cm working distancethat's supposedly, but it works fairly well.The ratio seems to be working great for smaller electronics ( NOT SMALL! ), because i can still measure my stove's temperature on the high side of a small spotand i have tried to measure a MLF package temperature ( that thing was burning up! i'll tell ya ... )