Handy temperature measurement tool

Discussion in 'General Electronics Chat' started by someonesdad, Mar 18, 2011.

  1. someonesdad

    Thread Starter Senior Member

    Jul 7, 2009
    For those of you who have access to Harbor Freight and are engineers and techs who like to measure things, I strongly recommend the little Cen-Tech IR thermometer -- see the attached photo. It appears that Harbor Freight doesn't sell it anymore, but it was in my local Harbor Freight store for $10 for years. They have a $25 one that uses a laser for pointing, but I can do without the laser, as the one I have is 65 mm long by 35 mm wide by 15 mm thick. It nicely slides into a pocket.

    I use this thing far more than I thought I would (I bought it about 4 years ago). For example, I've used it to find the hot component on a PC board. Right now I'm measuring the temperature rise of a wall wart at rated load inside a metal container and I just point and shoot. Of course, one needs to know the emissivity of the emitting surface to have an accurate measurement; this device uses a fixed emissivity of 0.95, which works fine for most things.

    I would have loved to have this thing when I was working in industry, as it would have been so handy when working in the lab.

    For more careful work, one first measures room temperature with e.g. an RTD, thermocouple, or thermistor. Then measure the device you're interested in after it's been sitting in the room a while. Then you can measure its temperature and correct for its emissivity and have good data. I don't bother doing this because I'm usually interested in temperature differences, but if I was, I'd do the correction by converting the temperatures to Kelvin, then calculating a multiplicative correction factor (because of the Stefan-Boltzmann radiation law). Then this can be used for further corrections. Of course, to be technically correct, you need to know that the emissivity doesn't change with temperature.
  2. studiot

    AAC Fanatic!

    Nov 9, 2007
    Don't you youngsters have it easy these days.

  3. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    Actually, that thing went on "sale" locally for about $4, when it was available. It was a great deal IMO. I bought several and gave them to my daughters and myself. They are great for heating soup. You set the electric burner to something between medium and high, stir and monitor for 145°F and the soup is ready in a few minutes. I wouldn't be without it. Of course, the aspect ratio is like 1:4 or 1:6, so it cannot be used for measurements of distant objects.

  4. debe

    Well-Known Member

    Sep 21, 2010
    This is 2 of them I use, very handybut not as cheep as you seem to be able to get them, these were about $30 Aust.
  5. strantor

    AAC Fanatic!

    Oct 3, 2010
    I tried to get one a while back, but couldn't get it approved as our calibration guy is scared of that big "E" word you mentioned. He has sworn off all manner of non contact temperature measurement devices in the plant as he can't put a calibration sticker on it and call it "good".