Scaling

I have a wonderware app communicating to a TI-555 plc. I have a wonderware tag that is displaying line footage coming from a drive etc.. Now, the wonderware tag is scaled 0-150000 raw and 0-150000 eu. I have to compare this value to a new register value. I created a new tag, tried to scale it the same as this and it appears that it is not linear. Not sure what's up with that.

It seems that when I try to scale the tag that I created, I can't seem to make it work. I can get one point to be scaled properly, but when I change the value, it is not the same. For example, if 33340 == 18199 counts, I can make that work but if 36840 is 18,225, then when I enter that footage, I get a totally different number.

I know that when the machine starts, the plc/drive puts a 16,900 in the footage value and that reads 0 on the wonderware. Not sure I really understand this because it is scaled 0-150000. This seems simple but i need a hand on this one.

Thanks,

I forget but maybe one of the TI gurus will showup, you might know or be able to verify it yourself.

I think the TI may be little endian, the LSB is first from the left, backwards from some. I really have no idea if this is or could be the problem but may be worth checking out.

Need more information.

Is this new tag reading a register in the PLC? Are you reading an analog value in the plc, and trying to scale it in Wonderware.

Raw analog values in the TI's for a 4-20mA signal are 6400-32000, it's 12-bit.

In TI the MSB is bit 1.

Allen-Bradley bits are like this: 15, 14, 13, 12, 11, 10....3, 2, 1
TI bits are numbered like this: 1, 2, 3, .....................14, 15, 16

I've never used Wonderware with TI, but in Intellution you have to specify what the LSB is in the TAG Database, I believe it's something like: LSB=0

If you can give more specifics, we can supply a more specific answer.

If this is a PLC register, why not do the scaling in the plc, there is a built in scaling function, very easy to setup, it's done from within a Special Function Program. If you already have a scaling SFPGM, then just add one more item.

yes, this is a V277 address in the plc.. I guess it is coming from the drives to display a footage count. I guess that it is possible that they are bringing it in from the drive, running it through a SFPGM to do the scaling and populating V277 with a value. Maybe I could find the scaling params in the SFPGM. There is not an LSB or MSB function in the wonderware like intellution. I would have thought that I could come up with a scaling routine by observing footage display from the counts in the plc but it appears to not be linear. I am not sure why that is the case. Any more suggestions??

Without knowing whose drive or what manipulation is being applied to the data, I would recommend first determining the entire path of this data value in the V-memory register; or at least to confirm what counts equals what engineering values minimum and maximum. It is likely that if it is a value from a drive over a network that it does not match the 0-32000 (6400-32000) counts that the TI uses. If this value comes into the PLC from an A/I then it should fall within this range if it is indeed connected to a TI A/I; if it is connected to a distributed I/O point it may have some other full scale counts / scaling.

Once you confirm the ranges for raw counts and engineering units, the solution should be fairly straightforward.


Tom

Can you post your TI program?

What type of data is this: "unsigned integer", "double integer", "real"
the upper raw limit you mentioned (150000) is too large for a unsigned integer (single word V277, would have a maximum range of 0-32000)
How is the tag configured in WW, "I/O Integer" "I/O Real"