Calculate acceleration (move function)

How the code block is called is kind of important. Consider showing us which tags are linked to the call of the code block. And please use ZIP to add multiple pictures instead of creating a new post.

If you are working with the HSC inside OB30, then use the :P as part of the symbol. The would cause an immediate read of the tag.

"myHSCValue":P

Are your tags that are not capturing the correct value DB tags?

If not, consider creating a global DB, add tags named AngularVelocity, VelocityNew, VelocityOld, and anything else you need for tags.

I have a DB named Tags for this purpose.

thomas_sigh

The HSC of course uses the immediate value, I calculate RPM and angular velocity as well without problems.

The AngularVelocity changes just fine and corresponds to the actual RPM fine. But somehow the VelocityNew and VelocityOld changes to the same value and never reflects the old and new value.

Temp values persist for the scope of the block the temp is declared.  Outside the scope they do not exist.  The next time the block is called, they start at 0 (or 0.0 or 16#0000 for example).

thomas_sigh

They are DB values, since they are called in a FB. AngularVelocity that's input for the block call is a Temp since it's a local variable of OB30. Is that the problem? 

I see now how your FB does not use TEMP tags, just IN/OUT/Static, which means that the only issue now is proper monitoring of the FB in operation.

That can be tricky, especially in multi-instance FBs.

In your case, open OB30, find the FB, right-click and use the open and monitor option.  I suspect you did that for your screenshot.

If you pass in a value for velocity, does it work?

Keep in mind, it's going to update visually on the screen much less often than the OB30 calls the FB, so you can miss things happening unless you artificially slow them down - like you did with the trace operation. 

thomas_sigh

Yes, I use the temp to transfer the output value from a block that calculates velocity to the block that calculates acceleration internally in OB30, so the every time the OB30 is called it should certainly be updated. Since both the high speed counter, the velocity calculator and the acceleration calculator is called in the same cyclic interrupt, it should function with a transfer from one block as output, to the other blocks input and it does give me a velocity when i test IRL.
So the value of AngularAcceleration I pass to the Calc_Acceleration should be transferred to VelocityNew and then the VelocityOld should hold the former value from the last call, but they end up the samevalue all the time. I've tried to subtract them and that value is 0 all the time, even when there's clearly a difference in the input value. Both velocityNew and VelocityOld are static. 

I've learned to avoid global tags, if not necessary, to avoid changing tag values in the wrong places. I don't see that could make a difference here, when the Velocity is correct and the blocks are contained in the same OB30, but I could be wrong??