TMP006 Environment issues

Hello Pragati,

What kind of material is the solar panel made of? I imagine it's some kind of shiny metallic material, which could be problematic for an accurate measurement with the TMP006. The reason for this is that the emissivity of such materials is very low, so it is not an effective radiator of the infrared energy that the TMP006 "sees" when making a temperature measurement. See the TMP006 User's Guide section 3.1 on emissivity: http://www.ti.com/lit/ug/sbou107/sbou107.pdf. If it's possible in your application, an easy way to improve the emissivity of a material is to paint a small area of it (the area within the TMP006 field of view) with dull black paint.

What kind of variations are you seeing on the local temperature? If the conditions are windy on the roof where you're measuring the panels, then these fluctuations might be just due to the cooling effect of the wind. If the local temperature of the TMP006 changes quickly enough, then this could also be causing errors in the object temperature reading.

The calibration factor S₀ is a gain error term which can be adjusted to account for various signal losses in a system. It is unique to each system, so to determine the appropriate value of S₀ in your application you should perform a two-point calibration at the minimum and maximum object temperature points. This is also described in the TMP006 User's Guide in section 6.

Best regards,

Ian Williams
Linear Applications Engineer
Precision Linear and Sensing Products 

Hello Ian,

Thanks for your quick response.

The solar panel is made of monocrystalline silicon cells. The panel is protected by a layer of white tempered glass and EVA resin with a weather proof film. 

We can't paint a small area with dull black paint. Also I am not clear about the S0

Further I am measuring the solar panel temperature with TMP006 EVM and one more temperature sensor as a reference.

The differences are huge as the other device measurements are almost stable whereas the measurements of TMP006 is very fluctuating ( you can see in the data attached)

I have taken temperature of solar panel with TMP006 and a reference IR sensor with emissivity of 0.96

Also if you can help me Ian in determining what is the distance beyond which TMP006 do not give proper results or what is the distance at which i can get maximum accurate temperature of solar panel. As of now I am placing the sensor as close as it can be to the solar panel, is it making any difference while measuring the temperature. Width, height & thickness of solar panel is 1318, 994 and 46 mm.

All the data are measured with calibration factor of 6.4E-14.

I am not able to find what I am lacking, hope you can help me as soon as possible.

Thanks,

Pragati

3252.DATA.xlsx

Hello Pragati,

If your solar panels are behind a layer of glass, then the glass temperature is all the TMP006 will be able to detect for two reasons.

• Glass is a great radiator with a very high emissivity
• Glass absorbs nearly 100% of the infrared energy in the wavelength range that the TMP006 detects (4μm to 8μm). This means that anything behind the glass is effectively invisible to the TMP006.

 I can not comment on the EVA resin without more information, such as a link to the manufacturer's data sheet.

Another potential issue with the measurement is that shiny surfaces in general will cause IR energy to "scatter" that can add significant fluctuation to a measurement with the TMP006.  Your attachment did not come through successfully so I am not currently able to see the data you mentioned in your most recent post. What type of IR sensor are you using as your reference? Is it some kind of handheld IR gun-type sensor? 

As for the S₀, per my previous message it is simply a gain term which can be increased or decreased depending on the amount of signal losses in your system. The default value of 6.4E-14 is a good general-usage value, but it's highly possible that it would need to be calibrated for your system. This is done by performing a two-point calibration as described in the TMP006 User's Guide.

The optimum distance is ≤ (1/2)*radius of a circular area of the object to be measured. For example, if you are interested in measuring a circular area of your solar panel which is 2 cm in radius, then the optimum distance of the TMP006 is 1cm away or less. There is no issue with placing the TMP006 closer. I've attached a screenshot from the TMP006 User's Guide which shows this.

 

Best regards,

Ian Williams

Hi Ian,

Yes, the reference temperature sensor is a handheld gun device. The data i have attached it again if still you are not able to see then i can mail it to you. Please give me your email address.

One thing which I am not getting Ian, is I am measuring temperature of solar panel  with TMP006 and also with this hand held gun like device. If glass is one of the reason for false readings then why it is not affecting the measurements taken with the reference device.

For the solar panel datasheet you can go through this website:

0486.DATA.xlsx

[View the data from the E2E post not your email]

Thanks & Regards,

Pragati

Pragati,

I also recommend that you enable the "Transient Correction" feature. Since you are taking measurements outside, this feature will help correct for errors caused by quick changes in local temperature (such as wind).

Best regards,

Ian Williams

Hi Ian,

Thanks a lot. You were right I was using the older version of TMP006. Now results with this new version of  TMP006 which you had mentioned are pretty convincing then it were earlier.

I am sending you two data of temperature measurements which I have taken with TMP006 sensor and the other reference sensor. These data  were taken in two conditions. One was in a room and other of the solar panel. The temperatures measurements of reference and TMP006 sensors taken in the room are almost same which is a good news. But thing which makes me ponder upon is the temperatures measurements taken of solar panel. The reference sensor has almost constant readings whereas the readings of TMP006 sensor are not constant at all. THE data of TMP006 matches with reference but for some time intervals only rest of the time intervals it overshoots or undershoots abruptly.

Can you help me in determining the reason behind this abrupt nature as well as the solution.

Thanks for your assistance and guidance.

Looking forward to your reply,

Best Regards,

Pragati5125.DATA.xlsx

Hi ,

Yes the transient correction feature was enabled. Putting the sensor in plastic and then taking the readings helped a lot in getting stable and correct readings.

Thanks for your help

Best Regards,

Pragati

Hello,

I just wondered if Ian could elaborate on the transparent plastic part of this post. We are looking to put a tmp006 inside a plastic case (to be attached to the body) to measure body temp, I'm struggling to find any specs on the type of plastic we would need to use in order to get the best results i.e. as transparent to IR as possible.

Any thoughts?

Thanks

Steve

Hello Steve,

There are two threads on the forum that discuss suitable cover materials for the TMP006:

• http://e2e.ti.com/support/other_analog/temperature_sensors/f/243/t/117229.aspx
• http://e2e.ti.com/support/other_analog/temperature_sensors/f/243/t/116631.aspx

Best regards,

Ian Williams