13
RATE SCALING
To scale the Rate, enter a Scaling Display value with a corresponding Scaling
Input value. (The Input value can be entered by Key-in or Applied Methods.)
These values are internally plotted to a Display value of 0 and Input value of 0
Hz. A linear relationship is formed between these points to yield a rate display
value that corresponds to the incoming input signal rate.
SCALING CALCULATION FOR KEY-IN METHOD
If a display value versus input signal (in pulses per second) is known, then
those values can be entered into Scaling Display (
x
) and Scaling Input
(
x
). No further calculations are needed.
If only the number of pulses per ‘single’ unit (i.e. # of pulses per foot) is
known, then it can be entered as the Scaling Input value and the Scaling Display
value will be entered as the following:
NOTES:
1. If # of pulses per unit is less than 1, multiply both Input and Display values
by 10 or 100 as needed to obtain greater accuracy.
2. If the Display value is raised or lowered, then Input value must be raised
or lowered by the same proportion (i.e. Display value for per hour is
entered by a third less (1200) then Input value is a third less of # of pulses
per unit). The same is true if the Input value is raised or lowered, then
Display value must be raised or lowered by the same proportion.
3. Both values must be greater than 0.
EXAMPLE:
1. With 15.1 pulses per foot, show feet per minute in tenths. Scaling Display
= 60.0 Scaling Input = 15.1.
2. With 0.25 pulses per gallon, show whole gallons per hour. (To have greater
accuracy, multiply both Input and Display values by 10.) Scaling Display
= 36000 Scaling Input = 2.5.
# of pulses per unit
3600
Hour
# of pulses per unit
60
Minute
# of pulses per unit
1
Second
INPUT (
x
)
DISPLAY (
x
)
RATE PER
RATE B DISPLAY VALUE FOR SCALING POINT 2
Enter the desired Rate B Display Value for the second Scaling Point by using
the arrow keys.
to
RATE B INPUT VALUE FOR SCALING POINT 2
Enter the corresponding Rate B Input Value for the second Scaling Point by
using the arrow keys. Rate Input values for scaling points can be entered by
using the Key-in or the Applied method.
to
Rounding values other than one will round the Rate display to the nearest
increment selected (e.g. rounding of ‘5’ causes 122 to round to 120 and 123 to
round to 125). Rounding starts at the least significant digit of the Rate display.
RATE B DISPLAY ROUNDING
INPUT FREQUENCY CALCULATION
The meter determines the input frequency by summing the number of falling
edges received during a sample period of time. The sample period begins on the
first falling edge. At this falling edge, the meter starts accumulating time
towards Low Update and High Update values. Also, the meter starts accumulating
the number of falling edges. When the time reaches the Low Update Time value,
the meter looks for one more falling edge to end the sample period. If a falling
edge occurs (before the High Update Time value is reached), the Rate display
will update to the new value and the next sample period will start on the same
edge. If the High Update Time value is reached (without receiving a falling edge
after reaching Low Update Time), then the sample period will end but the Rate
display will be forced to zero. The High Update Time value must be greater than
the Low Update Time value. Both values must be greater than 0.0. The input
frequency calculated during the sample period, is then shown as a Rate value
determined by either scaling method.
Courtesy of Steven Engineering, Inc.-230 Ryan Way, South San Francisco, CA 94080-6370-Main Office: (650) 588-9200-Outside Local Area: (800) 258-9200-www.stevenengineering.com
