point-to-point distance

[dlina]

Hi,

I need to measure a distance from the fixed object to a moving robot
And I need to do it in almost real-time.
Distance is up to few meters(say 1-5) and accuracy is not very important
I only want to know when I'm moving to or /away to the object and have about 5 different distance ranges (e.g. from far-way to very close)
What are my options?
I'm a new to this field so my impression is so far
1 Proximity sensors have to small distance
2. US/IR rangefinders can't fix on the particular target

It seems that I need some kind of tx to send US beacon and rx to measure beacon strength
Is thee any off-the-shelf product like that?

Thanx

 

[darcyrandall2004]

surely the robot has a number of encoders that provide feed back of its position. From this you should be ble to work out distance to a point.

 

[FvM]

Ultrasonic round trip delay with an active signal repeater would be an option, if no other communication channel exists. If you already have a RF or IR channel, an ultrasonic time-of-flight measurement could be used in reverse direction.