1

I want to measure the depth of a burning soil using IR proximity sensor. The sensor will be placed 20cm above the surface of the soil and measures it perpendicularly.

Problem #1: I'm quite concerned about the environment that the sensor is in, it would be hot (up to 60 degree Celsius) and dusty (as soil burning produces particulate (PM2.5). Will this two condition affect my measurement?

Problem #2 I was thinking that the temperature will, as any measurement device will have thermal drift, but the amount of thermal drift depends on the device itself, how sensitive it is to ambient temperature. Some source says that it changes the wavelength and thus makes the measurement inaccurate.

On the other hand, from some sources the smoke of the soil burning does not affect it too much because the IR wavelength is long enough to go past through the smoke..

Is this correct? If not please correct me and provide some reference

It will also be very useful for me if how much it affects the measurement is provided. Any ideas? I have no prior knowledge on this, so pardon if there's some mistakes.

el-cheapo
  • 385
  • 2
  • 12
  • Start by looking at the data sheet for the device. – Solar Mike Sep 04 '21 at 07:55
  • 2
    Problem 1. Proximity sensors are not temperature sensors. They detect changes in IR irradiance levels. Temperature sensors would need to measure IR wavelength and convert that to a voltage analog. Problem 2. An IR temperature sensor will measure the surface temperature only as that is where the IR irradiation is taking place. You can't measure the temperature at any depth using IR. – Transistor Sep 04 '21 at 09:38
  • 1
    IR proximity sensors use near IR. Thermal IR is long IR. – DKNguyen Sep 04 '21 at 16:31
  • Besides the previous comments, smoke and PMxx will certainly foul the sensor and change the intensity of any single frequency signal over time. You'd need some clever way of extracting your data without the benefit of predictable intensity (e.g. spectroscopic methods, flashing illumination), or else frequent calibration – Pete W Sep 04 '21 at 19:25
  • @DKNguyen and what are u implying be the near and long? I mean, what's the effect of using near and long? – el-cheapo Sep 05 '21 at 01:31
  • @PeteW By overtime, do you mean that it will be accurate for one time measurement but it needs recalibration to make sure the future measurement were consistent? Currently, I've been recalibrating it after each use, and the measurement itself is average value of 2.5minutes of continuous measurement (1 measurement every millisecond), so the measurement noise because temperature, smoke, and dust is diminished as I average it. Is that reasonable? – el-cheapo Sep 05 '21 at 01:36
  • @Transistor I'm not aiming to measure the temperature, but I'm asking whether the ambient temperature will affect the measurement of the sensor – el-cheapo Sep 05 '21 at 01:38
  • @SolarMike As for the data sheet, it only mention temperature, in which max operating temp is 70 degree Celsius. But I'm still wondering how much it would affect the measurement. Also, for smoke and dust isn't mentioned at all, and that's why I ask to this forum. – el-cheapo Sep 05 '21 at 01:44
  • OK. Can you clarify what you mean by "I want to measure the depth of a burning soil using IR proximity sensor."? Do you mean that you want to measure the *distance to* through (smokey) air to the top of soil? You can't measure depth of a solid by IR emissions at the surface. – Transistor Sep 05 '21 at 08:50
  • 1
    @bintangf_m - probably much slower. But you should be able to simply put your sensor in the smoky environment you plan for, with a calibrated IR source (which is kept clean), and see the drift in the baseline – Pete W Sep 05 '21 at 22:41
  • Wow @PeteW why I haven't thought about that.. that's a great idea – el-cheapo Sep 07 '21 at 14:37

0 Answers0