Red Lion LEGEND - Manual (Page 51)

Once the Number of Count Edges (NCE) to be used has been determined,
the Remaining Scaling factor required, “K
R
”, can be calculated. This is the
Total Scaling Factor, “K
T
”, divided by the Number of Count edges used as
shown in Formula #2:
FORMULA #2: K R = K T
¸ NCE
WHERE:
K
R
= Remaining Scaling Factor.
K
T
= Total Scaling Factor.
NCE = Number of Count Edges.
In our original example, the Total Scaling Factor, “K
T
” was determined to
be 0.041667. Since this value is less than one, sufficient pulse information is
being generated, i.e., there is enough resolution for the units selected. The
Number of Count edges can be left at the factory set value of X1. The Total
Scaling Factor, “K
T ”, therefore equals the Remaining Scaling Factor, “K R ”.
K
R
= 0.041667 ¸ 1 = 0.041667
If the remaining scaling is between 0.6000 and 5.9999, it can be
programmed directly into the Scale Factor value and the X1 factory setting
for the Count Scale Multiplier “SCM”, can be used.
COUNT SCALE MULTIPLIER
The general rule for choosing an SCM value is, when the Remaining
Scaling Factor, “K
R
”, is less than 0.6000, an SCM value of 0.1 or 0.01 can be
used to get a Scale Factor value between 0.6 and 5.9999 or to the point where
the maximum number of significant digits is obtained.
FORMULA #3: SF = K
R
¸ SCM
WHERE:
SF = Count Scale Factor.
K
R = Remaining Scaling Factor.
SCM = Count Scale Multiplier.
Following our continuing example, it is easy to see that the Remaining
Scaling Factor, “K
R
” (0.041667), cannot fit into the Scale Factor Value
without losing significant digits. Using the Formula above and a Scale
Multiplier value of 0.01 will allow us to get the maximum number of
significant digits possible for the Count Scale Factor value:
SF = K
R
¸ SCM = 0.041667 ¸ 0.01 = 4.1667
COUNTER SCALING EXAMPLE:
EXAMPLE #1:
A flow sensor provides 62 pulses per gallon. Calculate the scaling required
to provide a display reading in gallons. The number of “Display Units”
displayed after 62 pulses have been counted should be 1.
STEP 1 - Calculate the Total Scaling Factor, “K
T
”, using Formula #1.
FORMULA #1:
K
T
= Display Units ¸ Number of Pulses = 1 ¸ 62 = 0.016129
STEP 2 - In this application 62 pulses per gallon provides more than enough
resolution, so the “Number of Count Edges” (Selected in the Program
Counter Module) is set to a value of X1. With an “NCE” value of 1, the
remaining scaling factor required is still 0.016129.
FORMULA #2:
K
R
= K
T
¸ NCE = 0.016129 ¸ 1 = 0.016129
STEP 3 - To provide maximum scaling accuracy, a “Scale Multiplier” value
is chosen that will give the maximum amount of significant digits in the
Scale Factor. A value of 0.01 will result in a Scale Factor Value of 1.6129.
FORMULA #3:
SF = K
R
¸ SCM = 0.016129 ¸ 0.01 = 1.6129
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