I look for converting millivolt to Temperature..
Any blocks available for this in Libraries..Im looking for differentiator block..Under Which library will i get it?
Or if any other simple procedures are there to convert millivolt to temperature, Pls suggest the procedure..
What do you mean by "convert millivolt to temperature" ?
- If you are connecting a thermocouple then you need an AI835 I/O module.
- If you are converting a value from one unit to another in the PLC then its just y=mx+c. Unfortunately the AC800 basic libraries dont have a scale conversion block, but its only a few of lines of code to make your own.
The differentiator block is a "derivativeReal" and should be in ControlSimpleLib. I cant see that it is any use for converting a scaled value though :)
OK now your question makes a little more sense. Sorry.
The relationship between mV and temperature isnt linear and depends on your TC type. There are a number of sites on the internet that publish this info. I found this pretty easily - http://instrumentation-central.com/pa...
You can implement this using a lookup (x-y) table and thats probably the easiest way. AFAIK there is no purpose built TC fuction block in the AC800M libraries.
If you would rather calculate this, then the calculation for a K- Type themocouple is here -http://www.home.agilent.com/upload/cmc_upload/All/5306OSKR-MXD-5501-040107_2.h
Theres a really detailed treatment of thermocouples here - http://web.cecs.pdx.edu/~gerry/epub/p.... with the practical and usefull stuff appearing in the last 5 pages or so.
Of course, all this is built into the AI835 and duplicating this calculation seems a little excessive when its probably easier and more reliable to add a second temperature measurement to a redundant IO card. I also suspect the chance of introducing a simple bug into your calculation is quite high. Hence, my rather flipant initial answer.