good day

i have a problem with CSI 9800 reading. spot meter temperature read higher value than it should be. i have adjust the emissivity but it didn't work well. the minimum temperature seem to be the correct reading. need advice with this one

thanks

The temperature reading will average the spatial area contained in the pixel being measured. In fact, the spot being measured may contain multiple pixels. This is a relatively low resolution instrument. This means the spot size will be relatively large. When you measure the temperature, measure a target that is large enough so that you are sure the spot size will have a consistent temperature. Also, for test purposes, make sure you are measuring a high emissivity target so you do not have to worry about background reflectance. Finally, how far is the temperature off? I presume you are checking the surface with a thermocouple or similar device. BY the way, the 9800 is discontinued. It will be serviced by CSI until 2010. Of course, CSI does not manufacture this instrument, they relabel it. In the US, these are sold by ElectroPhysics.

This is most likely user input error!

When you say it is higher than it should be what do you mean, how do you know what it should be?
What type of material is it?
What emissivity setting did you use, and where did you get this from?
What Trefl did you use, and how did you work this out?
What enviroment is it in?
Can you upload the image, and a visual?

www.thermalvision.ie

thanks guys
Testtech, i don't this is a matter of resolution or pixel, because when i measure a wall or a floor which have a homogeneous temperature, it's still shows higher temperature. the temperature deviation is depend on the actual temperature, for example the deviation of human skin temperature is 8 degree C, the bearing temperature 65 degree C become 95 degree C. so the higher the actual temperature the bigger the deviation.

Bob Berry, beside the CSI 9800 we also have CSI 515 and device from Raytex that using laser to measure temperature. so i compare the reading from those three devices (with the same emissivity) and the CSI 9800 have higher reading than the others. the result doesn't related to the type of material that i measured, it's always higher. Trefl? what is trefl Bob?
i'll try to upload the image latter

thanks

Jasmine

The examples that you provide suggest a problem with the instrument. I think you will have to contact CSI and get their input and/or return it for service.

However, you should check each instrument for the emissivity setting and background temperature setting. The background temperature setting may be the Trefl. It is possible that you cannot enter a background temperature into one or more of the instruments. In that case, you need to determine what the instrument assumes for background temp. Remember, as emissivity increases, the impact of background temp decreases.

If the emissivity setting and the background temperature settings are the same, and you measure a large, high emissivity target and the measurement is significantly different from athermocouple measurement,and your comparison instruments, then the instrument should be serviced.

Hi Jasmine,

First of all, the Raytek instrument does not measure with a laser, the laser is only there to indicate where you are measurimg from. The measurement itself is infrared, like the camera.

The fact that both of these instruments give different measurements is not a surprise. Both instruments are probibly +or- 2 degrees or 2% whichever is the greater. This could account for a 4 degree difference in the displayed temperature, even with both having exactly the same inputs. Emissivity is only one input, and the spot radiometer probibly only has an emissivity input, wheras the camera has others. Unless the camera is setup with the same settings assumed in the spot radiometer, your displayed temperatures will be different, and the error will grow exponentially as the temperature increases. Both instruments also have a different spot size ratio.

If you have not already done so, get yourself along to a Level 1 class where a lot of this should become more clear.

jasmine
I'm a bit confused.
Both Bob Berry and Testtech give good advice.
But I didnt see in your post about a 4 deg difference in temperaturs. Is it just 4 deg or are the differences as you stated...."the bearing temperature 65 degree C become 95 degree C." as high as 30 deg C ?
If thats true, then you probably do need to send this unit back for re-cal.

Regards Jim P

thanks for the advice guys, you are right bob laser act as a pointer. Bob, are you familiar with CSI 9800 camera? if you do, could you help me to set-up this camera.
Jim, the different is 30 C, i have try the possible ways to change the setting, but it didn't work out.

You need to check this first.

What you need to do is measure an object of know temperature, with a known and high emissivity. The object needs to be at least 20C above the reflected enviroment. Validate your temp with a calibrated thermometer. Make sure everything else is input correctly. If the displayed temp is more then 2 degrees out (with all the inputs correct), send it back.

The 9800 is a perfectly good instrument if it is working correctly, i.e. in calibration, and used correctly. On a large surface, like the wall, where spatial resolution is not being challenged, two adjustments can be made to correct the measurement: emissivity and background.

If you don't have a calibrated black body reference, I suggest you look at a large, flat surface that is warmer than the room you are in—a gallon jug of warm water works well (well mixed). Set emissivity to .9 and background correction to the temperature of the wall behind you. The specification for the camera says the measurement should be plus/minus 2C. If you are off significantly (you decide what your tolerance is), the camera probably needs to be re-calibrated.

I'd also suggest, if you have not had basic training, that you consider both Level I and Level II courses. If I can be of further assistance, please let me know.