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Original question:

OPT3101: OPT3101

OPT3101: Calibration problem

user6095279
Prodigy 90 points
Part Number: OPT3101

hi

1. At present, I refer to OPT3101 EVM to design a module that is fully compatible with hardware, which can realize the distance measurement of 6 meters outdoors. However, after more than 6 meters, AMP_OUT is very small and the distance does not increase.And SIG_OVL_FLAG is not saturated.Is this normal?

2.In terms of batch generation, how many modules of data should be integrated for temperature calibration? 

3.I met a wonderful phenomenon, when I do measureIllumCrosstalk finished, my crosstalk data is less than 843, between 50-300.And cover the light module, amp_out less than 10, but iphase_xtalk_reg_hdr1_tx1 and qphase_xtalk_reg_hdr1_tx1.Every time a big gap, cause I am in distance measurement is not accurate.This is probably the reason why?

  • 0
    TI__Mastermind 25895 points

    Hi,

    1) depending on the averaging setting on OPT3101 and the target size/reflectivity yes this could be normal. Please see this app note for some data taken on OPT3101EVM and some ways to extend the range http://www.ti.com/lit/an/sbaa296/sbaa296.pdf

    With higher averaging we were able to get to 10m but the also was tested on a wall which is a large target size. SIG_OVL_FLAG is for too much signal saturating the device. This is the opposite where there is so little signal that signal to noise ratio become a problem. Also residual crosstalk can also cause issues if amplitude becomes close to the residual crosstalk level (more details in our intro to OPT3101 system design guide posted online ( http://www.ti.com/lit/pdf/sbau305 

    2) we recommend using 5 devices or more. More details here http://www.ti.com/lit/ug/slau791/slau791.pdf

    3) What do you mean by "iphase_xtalk_reg_hdr1_tx1 and qphase_xtalk_reg_hdr1_tx1.Every time a big gap"? For this question

    Best,

    Alex

  • 0 in reply to Alex Bhandari-Young
    Prodigy 90 points

    hi

    Thank you for your answer. What I mean by iphase_xtalk_reg_hdr1_tx1 and qphase_xtalk_reg_hdr1_tx1 is actually the illumination crosshair calibration value for the high current channel, which is the value loaded into the register.Do you mean that my crosstalk data is close to the signal strength at a distance, so I can't tell them apart?Can I improve the ranging distance of the module by reducing crosstalk?If I want to achieve an outdoor stable range of 8 meters, does my lighting crosstalk have to be less than 200?

    Have a nice day

  • 0 in reply to user6095279
    TI__Mastermind 25895 points

    Hi,

    Understood. So the raw crosstalk is around 300 codes and after correcting the residual crosstalk is 10 or less codes. This is pretty good and should give good performance. This means with amplitude down to 50 codes or so you should still get some data with crosstalk still being smaller than the signal. What is the amplitude you are measuring are you target max range? If amplitude is higher than this then you may need to play with increasing averaging to minimize noise and get good data. If amplitude is lower then either the target is not very reflective or the optics are not throwing enough light to get the needed signal returned for a good reading.

    Best,

    Alex

  • 0 in reply to Alex Bhandari-Young
    Prodigy 90 points

    Hi

    I see what you mean.That is, if the signal strength is close to the AMP after calibration at 8m, it is impossible to distinguish the signal from the noise.In addition, I would like to ask some questions about mass production.

    1. The led used by opt3101 evm is SFH213A and SFH4550.I fell can't improve this performance. If I don't want to use external lens, would you recommend other led models?

    2. At present, I want to calibrate 10 modules, and write the average value of calibration parameters into the code and load directly. Is it feasible?I'd better do the factory calibration recommended by the manual?

    3. The most important question is that the inner wall of the copper pipe I am using is not black. Is this a big influence?Or does it have to be black inside?

    Best

  • 0 in reply to user6095279
    TI__Mastermind 25895 points

    Hi,

    1. These optics are quite good for longer range applications if you are not open to using an external lens. I don't have a better component to recommend here. We also have data on the evm at ranges similar to yours in one of our app notes. http://www.ti.com/lit/an/sbaa296/sbaa296.pdf

    2. For the per unit calibrations you cannot do this as every unit needs to be calibrated in production. For the system level calibration, yes we recommend a process like this. A good rule of thumb is you can measure on a number of devices and if the values are very close then this can be averaged. We have found this is not the case for the per unit calibrations. Please see the calibration resources here for more details https://e2e.ti.com/support/sensors/f/1023/t/815766

    3. What copper pipe is this? I thought you are using the EVM in this test?

    Best,

    Alex

  • 0 in reply to Alex Bhandari-Young
    Prodigy 90 points

    Hi

    I did not use EVM, I designed my own hardware in accordance with EVM, and I totally referred to EVM, but compared with the EVM on the official website, the EVM copper tube in my hand seems to lack the black fittings on the inner wall of the copper tube.

  • 0 in reply to user6095279
    TI__Mastermind 25895 points

    Hi,

    This is used to prevent light reflecting sideways off the metal rings and the device seeing objects to the side of the EVM outside the field of view. The fittings slightly reduce range, but also block out these unwanted side effects. Using a custom part with larger aperture can reduce this range reduction. The fitting PN can be found in the EVM BOM. It is bivar c174 and available from digikey and others.

    Best,

    Alex