Numeric data display PV550

[ipaqmaq 0]

I have a 4-20 mA signal that I want to display as 0 - 1000 on a PV550 in a Numeric Data Display but in the Tag Edit box I'm a little lost. The two boxes marked "Scale" and "Offset" are what is confusing. Pull down the help box to try to get an explanation and get even more confused. Is there any body that can help me understand what they want. I believe the Min. and Max. in the Data Entry Limits take my raw counts from the PLC so I think I have that right but no matter what I try to enter into the Scaling boxes, I get displayed values that are not what I'm looking for. Thanks

[panic mode 246]

if you don't have good reason to do it the hard way, try doing scaling in plc using SCP instruction and leave PV display indicators to be just that - indicators. scale (a) and offset (b) are used in simple linear conversion in form y=ax+b usin SCP (scale with parameters) is much simpler in most cases. you just need to find out what 4 and 20mA correspond to and you are done (maybe 3277 and 16384?, read the analog card manual).

[Spedley 0]

If I remember rightly the PanelView multiplies the Tag by the scale value and then adds the offset. So if the Analoge card is set to read 4-20mA then the value from e.g I:1.0 would be 0-32768 (exclusive) so you would put 0 in the offset and 0.030517578125(1000/32768) in the scale value. and in general if Lo is the lowest value read from the input and Hi is the highest value read from the input then: Scale = (1000-0)/(Hi-Lo) Offset = (Lo+0) ... or something like that ! Edited 15 Sep 2005 by Spedley