VL53L4CD repeatability of small measurements

[anotherandrew]

I see from the datasheet that the indoor measurement accuracy at 1-100mm is +/-7mm. I’d like to use the sensor to measure the deflection of a piece of stainless steel, which is used as part of an actuator to hold an object still for measurement. Basically this bent piece of metal is going to be moved using a lead screw on a stepper motor until it makes contact with an object. The metal will deflect as squishes against the object, and I’m interested in trying to see the moment of deflection and gauging “how much�? deflection has occurred as a way to gauge how much force this metal is applying to the object.

The nominal distance from the sensor to the steel is ~5mm, and I would be trying to detect about 1-2mm of deflection at most. Now this is (very much) inside the measurement accuracy of +/-7mm so I know I can’t “trust�? the absolute distance reported, but the exact deflection amount isn’t important, just the fact that it’s deflecting. I don’t see a “repeatability�? specification in the datasheet, nor do I see any app notes which touch on this.

Is there any data for this sensor that could tell me what the repeatability of a measurement is, rather than its absolute accuracy at this sensing distance? Fortunately the environment is completely dark (in an enclosure) and both the temperature and humidity are precisely maintained (roughly 32C and 40% RH). I can also put an "idea" target sticker on the steel object that is moving.

Is this kind of application something that this sensor would be suitable for?

[John E KVAM]

the reason for the +/- 7mm is that the blackest black and the most reflective shiny surfaces return different values.

But if you can take a range on a specfic target, not caring about absolute accuracy, I'm very certain that you could detect if that surface moved by a couple of mm.

But don't take my word for it. But the VL53L4CD eval kit. (P-nucleo-53L4A1) or if that is not available buy the parts separately (X-nucleo-53L4A1 and Nucleo-F401RE). the P- stands for pack. But it might even be a bit cheaper to buy them separately.

For $56 you can convince yourself that this will work and you've only invested a couple hours.

The only issue I can see is that the Field of View is 18 degrees. So at some distance, D, the target diameter should be at least 1/3D.

Constant temp and dark only make the problem easier.

Good luck,

• john

[anotherandrew]

Thank you, I indeed am planning on testing this with an eval board. Just doing my homework first. 🙂