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advice on a simple pressure sensor?

Hi all,

I'd much appreciate any advice on my search for a cheap and simple pressure sensor. I need to make a device which can measure how hard a baby is squeezing a tube, around 2cm thick. I figure the best way is to use a silicon tube, just above atmospheric pressure, and connect it via a pneumatic tube to a pressure sensor. So what I need is a pressure sensor that does not have to be accurate in absolute terms, but needs to be relatively sensitive, so it can measure changes in grip strength. I reckon if it went up to 1000 kPa that would be more than enough. Preferably it would come with an integrated USB interface and drivers which provided an API. Alternatively, if you know a good one but it just outputs a voltage, perhaps you could also recommend a good cheap and cheerful USB A to D converter?

So far the best thing I've found is this, which you can combine with a USB interface from the same supplier:

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But I think it will only interface using their proprietary software - it's for classroom use, after all. But this gives you a basic idea of what I'm after.

Other solutions to the basic problem also gratefully received!

Cheers,

Ben

-- Dr. Ben Kenward Department of Psychology Uppsala University, Sweden

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Reply to
amorphia
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Presumably you will also need to correct for temperature - The baby's hand will warm up the air in the tube causing the pressure to rise even if they don't squeze it.

Reply to
CWatters
1000kPa is ~145PSI! It's going to be one strong baby?!

You're go> Hi all,

Reply to
blaildyors

Fill the tube with a liquid: less expansion.

Thomas

Reply to
Zak

Sensor would need to be waterproof.

The sensor I was thinking of was the motorola MPX2200A (0-29PSI) or similar (try googling for datasheet) - silicone tube would connect directly to the port on the sensor.

Reply to
blaildyors

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have 'quantum tunnelling compound pills', which work as pressure sensors - you could embed one or two in a piece of rubber and use that.

you could also try

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who sell a conductive rubber that changes conductivity when under pressure.

--
http://www.niftybits.ukfsn.org/

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Reply to
Andy Baxter

I seriously doubt if he'll get much of a reading at all from a silicon tube.

Silicone, maybe.

Cheers! Rich

Reply to
Rich, Under the Affluence

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1000kPa??? That's about 10 Bar or 150 PSI. What baby is going to be able to create that pressure squeezing on a tube? You're going to have to be about 100 times more sensitive than that, say 10kPa or 1.5 PSIG (gauge pressure) to be effective. That's about 100cm of water. Get a cheap pressure gauge and play around with it first before you try to instrument it. Bob
Reply to
Bob Eldred

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