Graphing analog signal

I have a 4-20mA signal which represents wind direction. 4mA = 0 degrees, 20mA = 360 degrees. When we graph wind direction you can guess what happens. When the wind direction is approximately North the value goes from 4 to 20 mA almost instantaneously, causing the trace to zoom up to max and then down to min constantly. I have no control over the transducer so I have to solve this one mathematically. This is in a GE 90-70 PLC and being graphed by Cimplicity 4.0 Any ideas?

I don't know that there's a 'solution' per se. 359.9° and 0.1° are at opposite sides of the graph, what do you expect it to do? IOW, what do you want the graph to look like once you 'figure out how to fix this'?...

I think what you really want is the graph to pass from the min to the max value without 'cutting across' the screen. It should magically reappear at the opposite end during a rollover, right? There's a name for this I remember from my video game days. When you move off the right side of the screen in Pacman, he 'teleports' over to the left side. I don't know Cimplicity, so I don't know if this is an option you can select.

One (lousy) idea... Decrease your sampling frequency to ignore intermittent rollovers...

beerchug

-Eric

I don't know Cimplicity either but could you made a circular graph? Then you may be able to make the "needle" rotate.
Probably another lousy idea but worth a thought.
beerchug

Since the wind varies from 0° to 360°, could you graph it as a sine, or maybe a sawtooth wave varying around zero? What I mean is, 0° to 90° graphs as the rising excursion in the positive region, 90° to 180° as the falling excursion in the positive region, 180° to 270° falling in the negative, and 270° to 360° rising in the negative.

graph

remove the line between each sample point now you would only see the datapoints.

What I actually have in mind is this - back in the good old days (around 1960 or so) we used what was called a 'quadrature potentiometer' to encode rotational position. This was a pot that had no stop and would turn freely in a complete circle. It had four terminals connected at approximately 90 deg. from each other plus one terminal for the wiper. (think of a wheatstone bridge.) By applying voltage to two opposing terminals, using the opposite two for a circuit common and taking the output from the wiper a sine wave was produced.
What I was hoping was that someone has done this in LM code. As you can see, wind direction would then graph as a sine with 0 and 360 adjacent to each other at the centerline of the graph.
There is no circular graph available in Cimplicity V4 although I remember seeing a VBX add-on for sale somewhere.