Liquid resin level detection

[Anonymous No.666927]

I'm builing a SLA machine and need a precise way to control the level of liquid resin in a reservoir and keep it at one hight. The hight doesn't need to be changable but acurate (0.01mm).

So far I have thought about:
-overflow system with pump (surface tension might fuck that up)
-diy laser triangulation
-float and switch

How would you go about acurate liquid level detection?

[Anonymous No.666930]

>>666927
If this is an integral part of SLA machine design, I'd check the existing solutions first.

[Anonymous No.666938]

>>666930
Thats what led me to laser triangulation.

[Anonymous No.666940]

are you sure you need this? I thought it was all about intersecting lasers and the liquid height didnt matter that much.

[Anonymous No.666952]

>>666940
You seem to be talking about something like US4041476 A

That's not what I want though.

[Anonymous No.667054]

I was thinking about solving this problem for a wastewater or fuel tank.

Capacitave displacement sensors can measure very high resolution. You could use a floater in a tube with a conductive metal disc on top.

Or use an off-the shelf laser displacement sensor. There are plenty of these on the market. If you want to do this yourself, get yourself a laser, linear ccd to measure the reflected beam, and a micropositioner (linear actuator or some way to make < 0.01mm movements) to assist you in calibration/development.

[Anonymous No.667344]

>>667054
Do you think I might get away with cleverly setting up a Webcam and laserpointer?

Also why use conductive top for capacitive sensor?
Isn't that for inductive ones?

[Anonymous No.667357]

>>667344
Capacitive sensors also measure displacement of a conductive target, afaik.

Webcam might work, off the top of my head its autofocus and automatic gain control could pose a problem... give it a shot.

[3dprintingfag !!XDLOZzmenCL No.667358]

>>666927
are you sure your positioning system can achieve that accuracy?

>>667344
Sure, if you can live with accuracy less than 0.01 mm. Though you will have to do the math to see what you can get.

Why are you use a pump to control your liquid level? Photopolymer is nasty!

Honestly, you're going to have a hard enough time as is correcting for polymerization shrinkage and other weird effects.

[Anonymous No.667364]

>>667357
Afaik capacitive sensors detect anything that qualifies as dielectric.
>>667358
>are you sure your positioning system can achieve that accuracy?
No. Positioning will be at 0.1mm. The liquid has to stay at the same level though.
>Why are you use a pump to control your liquid level?
Not dooing that. For level ajustments i can use a syringe with a linear axis. A pump would only be neccesarry if I use an overflow.

[Anonymous No.667369]

>>667364
>http://www.lionprecision.com/capacitive-sensors/
>Capacitive sensors (capacitive linear displacement sensors) are noncontact devices capable of high-resolution position measurement and/or position change - displacement measurement - of any conductive target.

[Anonymous No.667375]

>>667369
I see. I was thinking about a 2electrode type sensor. Thanks for clearing that up.

[Anonymous No.667826]

>>666927
have done somthing similar at work. Your best bet is a proximity sensor. We use capacitive proximity sensors for level detection in chemical supply tanks and lamination trouphs.

[Anonymous No.667829]

>>667826
*trough

[Anonymous No.667896]

>>667826
Alright. You got any advice on selecting one? I don't realy feel like buing multiple.

[Anonymous No.668199]

>>667896
>>>667826
> Alright. You got any advice on
> selecting one? I don't realy
> feel like buing multiple.
Instructable on how to make one.
http://m.instructables.com/id/Building-a-Capacitive-Liquid-Sensor/

here is one for 30 bucks, I have never used it though.

http://www.wolfautomation.com/products/25590/flat-pack-capacitive-level-sensor-3-wire-dcbr-carlo-gavazzi-cd50?gclid=CP_5772myL8CFcVDMgodKBAAiA

http://www.wolfautomation.com/products/22710/cylindrical-ac-or-dc-capacitive-sensors-18-or-30mmbr-autonics-cr-series

I am having difficuly findkng the one we use at work.

Remember, this will not work through metal, and I think the second sensor is teachable so you can vary the trigger distane a little bit.

[Anonymous No.668318]

>>667896


>>668199
still the guy who used this at work.

also keep in mind these sensors are binary. they tell when a fluid level has droped below a certain level. you can eitner set the system up to refil one the sensor is no longer satified then fill until it is. or use two sensors one for fjll and one to trigger the refil.

[Anonymous No.668463]

>>668199
How good is the repetition accuracy on these? The datasheet only lists Hysteresis I also couldn't find any Indicator to it while searching for other ones. Maybe i fail to see something.
>>668318
Binary output is no problem as long as its accurate

[Anonymous No.668984]

I also looked into pic related. Measuring resolution would be alright. But I failed to find a price on it and I'm unsure what "Low cost" would be. >100$, >500$ or >1000$ ?

[Anonymous No.669198]

>>668463
the accuracy (repeatability) should be pretty good since these are used to control industrial equipment and processes, but I doubt the precision is 0.01mm.