Using Fluke DAQ Software
Managing Your Network Using Fluke DAQ
3
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Every expression must refer to at least one channel or other measurement value
such as TOT. For example, the expression C101+1 adds one to the measured value
of channel 101, while C102**2 produces the square of the channel 102 value.
Expressions can refer to multiple channels, such as C201*C202, which multiplies
the channel 201 value by channel 202; if C201 is measuring voltage and C202
current, this calculated the power.
More complex calculations can be done as well, including calculations using or
done over time. For example, you could use an equation to calculate the rate of
flow in gallons per second. The rate of flow could be calculated as follows. Since
TS is in milliseconds, you need to divide by 1000 to calculate gallons per second.
In this example, during the first pass, C902 will not be defined and the result will
be not a number (#Inf). However, in subsequent passes, C902 will be defined and
will provide the correct result.
C101 = some other measurement to force the time calculation
C901 = (TOT-C902)/(TS/1000)
C902 = TOT
Note
You need one physical channel configured in the module that you're
scanning for this to work even though you're not using the channel in
the expression.
Computed channels and the time value are initialized to zero at the beginning of
scanning. Physical channels that haven't been measured are still initialized to
positive infinity.
To measure the total energy used by a simple system, a calculation could be
generated using the equation, energy = R x I^2 * time, as follows:
C101 = [Ohms]
C102 = [Current]
C959 = C101*C102**2*TS/1000
C960 = C959+C960
Note
This equation assumes that the resistance and current are constant
for the duration of the time interval. It also does not calculate the
energy used in the first increment of time.
In this example, C960 refers to itself. By doing this, it gets the value of C960 from
the previous scan, which allows it to calculate the total of all its values since
scanning started. In the same way, referring to a higher number channel in a
computed channel will get the value of that channel from the previous scan.
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