In situations where the Total Scale Factor is already in range of the Scale
Factor (0.0001 to 5.9999) and when there are no significant digits lost, the Total
Scaling Factor, “K
T
”, can be programmed directly into the Scale Factor Value
and a Scale Multiplier value of 1 (the factory set value) can be used. For example;
if the display units are in feet and there are 100 pulses per foot, the Total Scaling
Factor, “K
T
”, would be 0.01 ( K
T
= Display Units/Number of Pulses = 1/100 =
0.01). Since the Total Scaling Factor, “K
T
”, is exactly 0.01, it can be programmed
into the Scale Factor Value, “SF”. The Scale Multiplier Value, “SCM”, can be
left at or programmed to its factory setting of x1.
After the Scale Factor and Scale Multiplier values are selected, all that is
necessary to complete the scaling is to choose the Rate Conversion Factor. The
Rate Conversion Factor can be selected to provide indication in Rate per Second,
Rate Per Minute, or Rate per Hour.
Note: There may be situations where there are many more pulses per display unit
than needed. In these situations the minimum SCM value (0.01) may not
provide enough significant digits in the Scale Factor. To achieve more
significant digits, the Rate Conversion Factor should be set to mode 1, Rate
per Second, and the following formula should be used.
SF = K
T
x CF
SCM
Where:
CF = 60 for display reading in Rate Per Minute, or
CF = 3600 for display reading in Rate Per Hour
SCALING DISPLAY C
In the Speed Ratio and Speed Draw modes, [41 2,4], Display C can be scaled
in order to obtain the desired amount of decimal point resolution. This is
accomplished by selecting a “Display C Multiplier” and the proper “Display C
Decimal Point & Leading Zero Blanking” mode.
In the Speed Ratio and Speed Draw modes the Gemini 5200 performs the
appropriate Display C calculation based upon the measured internal rate value,
utilizing the total number of significant digits available to it. It does not use the
amount of resolution that is used in the Rate A & B displays. For example; if the
Gemini 5200 was set-up in mode [41 2], Dual Rate with Speed Ratio, and the rate
indicators were programmed to indicate rate with no decimal point. With actual
rates of 1.5 PPS for Rate A, and 1 PPS for Rate B the rate displays would both
read 1, however, Display C, when using a Display C Multiplier of 10 and a
decimal point, would read 1.5 (C = A/B = 1.5/1 = 1.5).
RATE SCALING EXAMPLES
EXAMPLE #1:
A 60 tooth gear is mounted to a roller that has a circumference of 2 feet. It is
desired to have a rate readout in 10ths of feet per minute. Calculate the Scale
Factor and Scale Multiplier values necessary to provide the desired readout.
In this example one revolution of the roller will provide 60 pulses for 2 feet of
linear travel. Since the desired display units are to be in tenths of feet, it is
necessary to convert 2 feet to tenths, giving us 20 tenths (display units). The Total
Scaling Factor, “K
T
”, is calculated by simply plugging in the two numbers into
formula #1.
K
T
= Display Units/Number of Pulses
K
T
= 20/60 = 0.333333
In order to get the maximum number of significant digits in the Scale Factor
we use formula #2 and a Scale Multiplier value of 0.1 as shown below.
SF = K
T
/SCM
SF = 0.333333/0.1 = 3.3333
To obtain rate indication in Feet Per Minute, the Rate Conversion Factor is
programmed for Rate per Minute mode. A decimal point is also added to provide
for a display of feet in 10ths.
EXAMPLE #2:
The shaft of a positive displacement pump has a 14 tooth sprocket that is being
sensed by a magnetic pickup. It is known that when the unit is pumping 810 liters
of water per minute, the shaft is turning 400 RPM. It is desired to have a display
readout in liters per minute.
With the Gemini 5200, it is not necessary to deal with time unit conversions. From
the information given, we know that when the shaft has turned 400 revolutions, 810
liters of water will have been pumped. The first step we need to take, is to calculate
the number of pulses that occur when 810 liters have been pumped.
NUMBER OF PULSES = # of Revolutions x Pulses per Rev.
NUMBER OF PULSES = 400 Rev x 14 Pulses per Rev = 5600 pulses.
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Summary of Contents for Astro Line Series
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