I am considering the ISL29501 sensor for an application. I got the EV kit to be able more rapidly put together a prototype to test the ranging functionality, but I am unable to get even close to the readings I am supposed to.
I followed the video on the product page and then noticed that in the video, the device is calibrated to 30cm, but the measured distance displayed just below Reference distance is 259cm? I also see the calibration offset. Does this then mean that values measured thereafter will be correct?
I this normal behavior?
Thank you for evaluating our optical sensor. I have a couple of questions regarding your application. Can you please tell me what distance you want to measure through our EVK and also share the picture of the reading for me to better understand your query?
Hi Raja -
Sure, I will gladly answer your questions. The application has actually been registered with Renesas, it is a water level sensor that will be utilised in harsh conditions. We need to achieve minimum 4m range, but hoping to get to 6m or 8m. The challenge lies in IP69 requirement by the client.
We are currently using the ST VL53L1CD sensor inside a SERPAC enclosure to ensure the IP69 rating. The problem we are facing is that the VL53 sensors experience a lot of crosstalk due to the 3mm thick transparent enclosure. It is ok for distances below 1.5m, but anything further than that and the readings are all over the place.
I recently received the Intersil sensor and started testing yesterday. The test was simply done on my bench, not inside the enclosure. I think I need a better understanding of how the offset works, is this a constant that we will need to keep in consideration for all measurement after calibration has been done? Or is the sensor suppose to give the correct readings after calibration?
I was using the software that came with the EV kit.
Thank you for your detailed explanation. Our ISL29501 can measure distances up to 2 metres, and the typical accuracy is ±10 cm across temperature and ambient. The development kits or evaluation boards are for a 2-meter sensing system. The ISL29501-CS-EVKIT1Z kit and the ISL29501-ST-EV1Z board also allow quick evaluation of the ISL29501's performance for a 2 m sensing system. The ISL29501 has the ability to perform real-time correction of distance measurements due to changing temperature and ambient light conditions. The chip can be programmed to correct the offset.
Yeah, the sensor will give correct reading after calibration. For most applications, three calibrations must be performed on every board i.e., standard calibration, Crosstalk Calibration and distance calibration. For more details, please see the attachment also shared some application notes (link given below).
*AN1983: Best Practices for TOF Crosstalk Calibration (renesas.com)
AN1984: Temperature and Ambient Light Error Correction (renesas.com)
Thank you for your prompt response. Is the 2m limitation only applicable to the EV kit or to the ISL29591 sensor in general?
I will set it up again today and see whether I can get accurate readings under 2m. I did follow the instructional video and went through all three calibration steps as you mentioned. I will do this again today.
The Basic principle is that our chip uses phase detection to determine distance. Because it operates at a fixed frequency the phase detection can only work until the phase changes a limited portion of a modulation cycle. This limits the measurement distance to the low meter range.
The evaluation kit / board measures quick evaluation of the ISL29501 performance for a 2m sensing system. Apart from that range of system can be optimized (up to few meters) for different application by connecting external photodiode and Emitter.