I have some AIs like that.
I deal with the input using a CALC record
just as you suggest for your outputs.
Pete.
-----Original Message-----
From: Gavin Smith [mailto:[email protected]]
Sent: 29 March 2005 07:37
To: [email protected]
Subject: Logarithmic conversion / Breakpoint tabes
Hello All,
I have an Ai record which gets raw data from a pressure (vacuum?) sensor
measured by the PLC. The raw data ranges from 0 to 256000 and represents
a Torr of 1e-11 through to 1e-3. I am wanting to convert this into the
engineering units, but as far as I can see only linear styles of
conversion are supported. I could make a breaktable with some values in
it, but if I understand correctly the gaps between the points will be
interpolated linearly, and will therefore suffer some error.
In addition to inputs, I need to have a couple of Ao's, representing
maximum allowable pressures, etc. My current thinking is to have a calc
record for each sensor to evaluate something like CALC,"exp(A/3200-4)",
and for the outputs having an ai feeding a calc feeding an ao record for
each one.
How are other people handling this in their systems? Extra records, big
breakpoint tables or some other way?
Thanks,
Gavin Smith.
(I'll be away from the office till next week sometime, so don't think
I'm snubbing anyone by not replying to them straight away).