E Computed Channel Equations; Computed Channel Equations - Fluke 2680A User Manual

Computed Channel Equations

Introduction
An equation is converted into a stored binary format which is sent to the 2680
Series or NetDAQ instrument where the calculations are performed during the
processing of each scan. Constants are passed to the instrument as single precision
(4 byte) floating point numbers which have a maximum magnitude of
3.402823E38. Calculations and intermediate values in the instrument use double
precision (8 bytes) in order to preserve resolution. The resulting computed channel
value is a single precision floating point number. When the result is >9999.9E+6
or<-9999.9E+6, Fluke DAQ displays +OL or -OL for that channel, and changes
the channel value to +1.0E+9 or -1.0E+9, according to the sign.
The instrument traps math errors such as divide by zero and log (0) and returns a
non-numeric result which the Fluke DAQ reports as +OL. If a the value of a
reference channel is non-numeric (indicating an open thermocouple or overload),
the value +1.0E+9 will be returned for the computed channel.
Computed channel equations must observe the following syntax:
•
White space is allowed, but not required, between symbols.
•
White space and parentheses do contribute to the 250 character limit for the
text string, but do not contribute to the size of the stored binary equation (all
stored binary equations for a 2680 Series instrument cannot exceed 6000
bytes).
•
Alphabetic characters may be in upper or lower case.
The symbols used in the syntax definition have the following meanings:
<> enclose an element which needs further definition
{} enclose elements that may be present zero or more times
[] enclose elements that may be present zero or one time
Appendix E
E-1