Hello, this is very urgent.
Could anyone please suggest for me a sensor that measures the distance between two points (NOT the distance of the object in front!) I need to put two pieces of this sensor and measure the distance between only these pieces. I have looked everywhere and it seems really complicated to find a solution for it 
Thank you.
As you say... a "distance to thing in front of me" sensor is more readily available, well developed, supported, etc.
Have you considered putting one of those on the end of a long-enough lead?
Please tell us the sorts of distances you want to measure, and the resolution that you want, to save irrelevant answers.
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How about something like the sort of compass used to draw circles, with a potentiometer in the "hinge"?
There's a recent(-ish) thread somewhere about a guy who used ultrasonic, but with transmitter and receiver on different objects.
He used low power radio on the transmitter end to send a radio message to the receiver end to say when the ultrasound pulse was sent. On the assumption that radio is instantaneous compared to sound, he then clocked the incoming ultrasound and knew its time-of-flight.
I have no idea who the poster was, nor the name of a member who iirc gave him huge help on the synchronising.
But I thought at the time, "that's bloody clever".
tkbyd:
As you say... a "distance to thing in front of me" sensor is more readily available, well developed, supported, etc.Have you considered putting one of those on the end of a long-enough lead?
Please tell us the sorts of distances you want to measure, and the resolution that you want, to save irrelevant answers.
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How about something like the sort of compass used to draw circles, with a potentiometer in the "hinge"?
the use is that I need to measure the distance between a person and an electrical wire in order to stay far from it (at least 30 cm). Arduino will be planted with the person and will warn him once he's too close. I don't think the resolution is too important here. what's important is having sensor points in multiple places in his body as well as the wire.
bakafel:
an electrical wire in order to stay far from it (at least 30 cm).
Engineer in me says I'd go for a solution that makes the wire safe in the first place, not try to keep someone away from something dangerous.
ardy_guy:
Engineer in me says I'd go for a solution that makes the wire safe in the first place, not try to keep someone away from something dangerous.
Do not worry that's not the problem. the wire is already safe but we need to keep far from it at least 30cm. and a technician may need to work nearby that's why it is needed
Your idea is totally impractical. There are no such sensors, but feel free to waste your time looking.
Better to put a cage of diameter 30 cm around the wire.
Can you connect the Arduino to the wire? It sounds like it's high voltage or something. Without that, you are measuring the distance from every point on a human body to an imaginary line in space. That is a very difficult task. Maybe you could do it with a Hollywood motion-capture rig but then you'd need a budget like James Cameron.