How to make a constant calculation of the remaining length?

Thanks.

So, now, I have a length that I can give in myself ( in cm), and an analog value that's converted to a speed in cm/min. 

Is there a way to make a constant calculation of the remaining length?

So: the length that I gave in should be constantly reduce, dependent on the speed (analog value).

Purpose is to unroll a coil with fiber at a certain speed (analog value) and to know when the coil will be empty. In best case, we can constantly see the remaining length on the coil.

Thanks in advance

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Split from Enter a value on the TDE.

Like you see above, I now have a little program: every second, the mathematic function does a calculation of the inserted value (here 10000) minus the analog (amplified) value (here 186).

But in fact, he should take every second the new calculated value (here 10000-186 = 9814) minus the analog value, and that over and over again. I should see the calculated value reduce every second.

Is that possible?

Thanks in advance

ixo65

Here an example.

 Thanks a lot! I'll try to understand that now :D

Thanks for that!

Now I made the program myself, but seems like there's still something wrong. When I enable the I1, to start the cyclus, it doesn't start from the given value (here 10000) but it starts reducing from 0.

Any idea what I do wrong?

Thanks in advance

For the moment, my analog value is still in cm/min; but I reduce my given value (10000) every second.

So, I have to divide my analog value by 60 to have it as cm/sec. But the problem is, the accuracy isn't good at all, the final value only changes when the initial value is a multiple of 60.

Should there be a way to solve this?

I can just let it be in cm/min and only reduce my value once a minute, but then there's also some accuracy problem.

Thanks in advance

I'm sorry, I'll try to explain it better.

So I have a 0-10v signal, what in fact is a speed of 0-8 m/min.

But in Logo, I can't scale accurate between 0 and 8, so I do it between 0 and 800. Because of that scaling, the unit becomes cm/min.

Value I give in by hand is the length of the rope on the coil, in cm (here: 10000)

Becaus of the fact I reduce that given value (10000) every second for the moment, the speed value (0-800) does also have to be reduced by 60; to become cm/sec.

So for example: speed of 4,2 m/min: after the calculations in Logo: 7 cm/sec. 

The value of 10000 has to be reduced by 7 every second.

But my problem now is the conversion from the speed from cm/min to cm/sec. I have to divide by 60, but because of that, the accuracy is not ok.

By example: 116 cm/min becomes 1 cm/sec; but 124 cm/min becomes 2cm/sec: little difference, but huge difference in outcome