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1.2
Application Note
1.2.1
RATE - Frequency Measurements
The Flow Indicator can be used as a basic frequency counter simply by inserting in the front panel
thumbswitches the value of one second or decimal equivalents. The gate time of one second will
transcribe the input signal into frequency directly in terms of cycles or pulses per second. A setting of
.100000 X1 is one second. One second may also be set by .010000 X10 or .001000 X100 or .000100
X1000. With a one second gate time, the readout displays directly in Hz (XXXXXX Hz). When using
settings other than 1 second, care must be exercised to mentally locate the decimal point. Starting
from a setting of .010000 X10, the display can be expanded in either direction simply by changing the
multiplier (.010000 X1 = XXX.XX KHz and .010000 X100 = XXXX.X Hz). Scaling of frequency readings
may be extended to the limits of the time base range. (See Specifications, Section I for limits.)
Normalized Rate
Normalized rate measurements are special cases of frequency measurement. Specific applications
include the quantizing and displaying of shaft rotational rates (tachometer) liquid flow rates (turbine
flowmeters) and speed indication of production line or conveyor belt systems. The CF-604 features
high input sensitivity which is compatible with the direct output of a variety of widely used
electromagnetic transducers.
The ability of a counter to vary its time base has greatly extended the usability of rate counters.
Proper adjustment of the time base makes possible direct readout in basic engineering units such that
troublesome conversions are completely avoided. This ability to read directly also avoids costly errors
in calculations and speeds identification of system problems by quick identification. Selecting the
proper gate time is the most critical factor in this type of counter. However, once one acquires an
understanding of what is occurring within the counter, normalized settings may be derived quite easily.
Normalized rate is accomplished by adjusting the gating interval of the counter so as to sample only
that portion of the input signal required to provide the proper display.  If we have a sensor, for
example, delivering 100 pulses for each revolution of a shaft, then in order to read RPM, we only want
to display 1 for every 100 pulses received. With a rotational rate of 1 RPM and a gate time of 1
minute, the counter would obviously display 100.
1-14

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