JoMo

01-23-2008, 05:24 AM

Hi,

I have a·question about making time measurements. Which·may be painfully obvious to do. (It's just that I am good at missing the obvious, especially the·painful variety).

Here is the scenario:

I want to measure the distance traveled using a single·3-Axis accelerometer to determine my position

(relative to the initial start of events) and·display that·position in real-time (every few milliseconds).

The entire event would take place in a small area, a room for example, and would last a only a few minutes.

I know that the method of using an accelerometer to do determine distance·will·propagate any errors introduced, but I hope that won't be a big problem·if the·distance traveled and·over all begin/end elapsed time is relatively short (distance being reset at the start of each run time).

Since I would like·the position granularity to be smallish (to the centimeter or so) that leaves GPS out.

Alluding to a side question: How would you·go about measuring the current position of something·during a·walkabout in a room? Since GPS won't help me, the accelerometer was my next approach.

But my main question here is:

Using the Prop, what would be the best method for measuring the time from start of the event

so that I can use that value to calculate the distance traveled in real-time?

Could I simply start a new cog that waits every nth milliseconds which then increments a counter?

Where if·n=10·then 10 counter hits = 100 msecs.· Is there a better way?

thanks

-Joe

·

I have a·question about making time measurements. Which·may be painfully obvious to do. (It's just that I am good at missing the obvious, especially the·painful variety).

Here is the scenario:

I want to measure the distance traveled using a single·3-Axis accelerometer to determine my position

(relative to the initial start of events) and·display that·position in real-time (every few milliseconds).

The entire event would take place in a small area, a room for example, and would last a only a few minutes.

I know that the method of using an accelerometer to do determine distance·will·propagate any errors introduced, but I hope that won't be a big problem·if the·distance traveled and·over all begin/end elapsed time is relatively short (distance being reset at the start of each run time).

Since I would like·the position granularity to be smallish (to the centimeter or so) that leaves GPS out.

Alluding to a side question: How would you·go about measuring the current position of something·during a·walkabout in a room? Since GPS won't help me, the accelerometer was my next approach.

But my main question here is:

Using the Prop, what would be the best method for measuring the time from start of the event

so that I can use that value to calculate the distance traveled in real-time?

Could I simply start a new cog that waits every nth milliseconds which then increments a counter?

Where if·n=10·then 10 counter hits = 100 msecs.· Is there a better way?

thanks

-Joe

·