How to measure level of sand in a bucket/tank

[nft007]

I need to remotely determine the level of sand in a tank.

Once the sand levels in the tank are low, I want to receive a notification or turn an LED on (so to remind me to refill it).

I was wondering if there were sensors out there that could help me with this.

One idea I had was to have a proximity sensor attached to the lid of the tank that would point straight down to measure the height of the sand pile (once it reached half the tank height I would turn an LED on).

This is probably a bad way to do this and I want to implement a more elegant/accurate system.

Help/advice would be appreciated!

[ieee488]

maybe a load cell
maybe ultrasonic sensor

[CrossRoads]

Get an ultrasonic sensor and try what you suggested in your original post.

[polymorph]

Is it always dry sand, or can it sometimes be damp? Is the composition of the sand always substantially the same?

[MarkT]

Another possible approach is a light-beam across the tank that would be broken if the sand is high enough.