Small Submersible Load Cell

Try www.800loadcel.com

Contact Honeywell.

It wouldn't happen to be part of your MQP would it?

You might want to try Omega but they are not cheap.

http://www.omega.com/pptst/LCFA.html

You will be looking at an estimated price of $600. There are cheaper alternatives depending on your requirements.

Cheers!

'85

Check out Rice Lake Weighing systems.

Thanks for the feedback everyone. But does anyone know if you could get a small load cell for less? I will probably need 4 of them for under $1200.

I just found LoadStar sensors who sells load cells for $300 apiece, with a built in amplifier to usb (something only Futek can offer, but for a rediculous price). But they are not submersible.

SO I guess another question would be, could I make a load cell submersible up to 1m and if so, how?

-Estefano462

BTW, it is not for my MQP (that is already done, thank god)

Are you an EE or would you need to talk to someone in Atwater Kent?

Depending on the requirements of the load sensor (mechanical properties, stiffness, length, etc.) you can roll your own with some high resistance wire and a Wheatstone bridge. You could suspend the load to be measured from a piece of wire that is one leg of a Wheatstone bridge. The resistance of that section of wire will vary by the tension applied. You would then need to calibrate the output of the Wheatstone bridge to the weight applied.

It will take some experimentation to find the best combination of wire material, AWG size, bridge resistance values, amplifier design, weight pre-load, linearity, etc. Analog Devices make some nice IN-AMPs to make the amplifier part easier. They also have an excellent reference on Sensor Signal Conditioning.

http://www.analog.com/static/imported-files/seminars_webcasts/49470200sscsect2.PDF

I've never attempted this in practice so I don't know exactly what you're in for, but it might be worth a few hours in the lab to see if you can make it work($$). My gut feel is that you might want to start with some iron based wire but do some research and see what metals are used in strain guages. Since the load is very low (2 pounds) I would start with some fine guage wire perhaps 30 AWG or even smaller.

Good luck with your quest !!

'85, '95

No I am not an EE, so much of what you have suggested is foreign to me, but not out of the question. Much of my project has been to set up instruments in labview, so any device with a simple voltage output is what I need.

I have looked into analog devices, and the idea seems reasonable at a glance. I could go with a wheatstone bridge, but given my severe lack of EE experience, it would be more trouble than it is worth with the close of my project a few months away.

However, how would you make a circuit that you spoke of submersible? would it simply be a dip in epoxy? I think I can find something suitable, the question is can I put it in water.

-estefano462 , 09'

Ideally, you would like the amplifier and the Wheatstone bridge as close as possible to the sensing element for EMI reasons more than anything else, (I'll ignore temp coeff of lead wires, etc.) but there is no real reason why you couldn't have the "sensor" submerged and just remote the rest of the bridge and the amplifier to above the water surface, unless of course you are working with an underwater vehicle. Like you say, you could encapsulate the whole thing in epoxy which would work for a while. You have to watch the "penetrations" where wires go into and out of the epoxy because water has a way of finding it's way in eventually. Typically, you will have to "prime" the insulation on the wires or you won't get a good bond with the epoxy. For a quickie project you probably won't have to worry about it though. I work with underwater systems and keeping water out is always a big challenge. We have experts on adhesives working here as well as folks who do nothing but worry about corrosion effects. The way we keep things dry tend to be bulky and heavy or use some pretty sophisticated adhesive and epoxy systems in a carefully controlled assembly environment. PBOF or pressure balanced oil-filled systems work well, but probably not necessary and definitely outside the scope of your project.

Cheers!

Hey, this just popped in my mailbox courtesy of Product Design and Development.

http://www.pddnet.com/product-futek-offers-new-subemersible-miniature-load-cell-010510/?wnnvz=1750,01274398578

This just might do the trick. You should check out the Futek website. You might also be able to sweet talk yourself some samples too. Often the manufacturers have a soft spot for students because they eventually become engineers and might remember the company later when they need a (fill in the blank here).

Cheers !!

P.S. Ouch, just checked their website. About a grand each. However, if the device meets your requirements, give their sales office a call. They may very well be willing to send you samples that might not meet their specs for sale, but could very possibly meet your requirements. Worth a shot. They even have a 2 lb version.

http://www.futek.com/files/pdf/Product%20Drawings/lsb210.pdf

Just thought of someone else, http://www.sensing-systems.com/.

They have submersible load cells and they will custom build. Not sure about pricing but, they probably have what you are looking for.