Homebuilt Rov Forum

Exploring the Hobby of Building your own ROV - Imagine, Create, Inspire.
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PostPosted: Dec 17th, 2015, 4:58 am 

Joined: Oct 17th, 2015, 1:10 pm
Posts: 10
Location: Portugal
Did you performed any voltage readings and comparison to depth? The voltage output directly proportional to depth?

PostPosted: Nov 21st, 2017, 6:33 pm 

Joined: Nov 18th, 2017, 7:18 pm
Posts: 8
Did you get your depth gauge working?
This looks like an interesting place to start for a uROV project, so I've been looking at the devices suggested above.

G1/4 Pressure Transducer Sensor 0-10MPa for Oil Fuel Diesel Gas Water Air
10Mpk equates to about 1000M of depth, and the output voltage ranges from 0.5 - 4.5 V (4V range)
sea-level would be 0.1 Mpk

If we assume that we use a standard microcontroller (no Amps) to read the device with an ADC of 10 bits (1/1024 resolution over 5V e.g. the smallest voltage we can resolve is about 0.0048v)

Our signal will be covered by 4/5 of 1024 or about 1/820th resolution so (ignoring any errors in the system) we would have a resolution of about 1.2M (3.9') depth. i.e. we can hardly identify a difference in depth from our head to our toes.

With a 1.5% full scale error (linear?) You could be anywhere!
To improve the resolution you could expand the signal so it maps from 0.5-4.5 into 0-5V, or amplify the signal (with ranges that normalize to 0-5V), or use a higher resolution ADC (each bit doubles the resolution). All of these methods can significantly increase errors into the system.

It should be noted that an understanding of the significance and difference between error and resolution is important.

I'm quite interested in autonomous operation, and so resolution is important to me. I'm also assuming that waterproofing much past 30M is not a trivial problem, thus a sensor having a FSD of just a few 10s of metres will suit me. So a '50M' device with similar characteristics would increase resolution to 0.06M or 60mm!

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