Red Lion LEGEND - Manual (Page 9)

BASIC OPERATION
The unit contains a counter that keeps track of the input pulse count. The
unit takes the actual number of pulses counted (internal count value) and
multiplies them by the Count Scale Factor and Count Scale Multiplier. This
results in the desired reading value for the Count display.
The Counter has three Reset Action modes associated with the display;
Reset to Zero (up-count modes), Reset to Preset (down-count modes), or
Reset to the Counter Load value. A Reset can be a manual reset, using a
programmable User Input, or it can be one of the seven programmable
Automatic Reset modes. Both the reset action and automatic reset modes are
programmed in the Program Counter Module.
The Counter displays the scaled number of pulses that have been entered.
When the count equals a Preset, the appropriate output will activate. The
count can be programmed to automatically reset.
During operation of the Legend
Plus, af ter internal scaling is
complete, any digits remaining to the
right of the least significant digit
(LSD) of the display is examined by
the unit. If this digit is equal to or
greater than 0.5, the LSD of the
display is rounded to the next higher
digit. Any number less than 0.5 is
ignored. During Reset to Preset
modes of operation, any remainder
greater than 0.5 will cause the display
to be rounded up. Due to this rounding
action, the output activation may
appear to be delayed. In actuality the
display may have rounded up or
down, but the internal count had not
yet reached the preset value or zero.
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The signal at Input A is used for the Rate indicator. The rate indicator uses a
time interval method (1/tau) to calculate the rate value. The unit counts on the
negative edge of the input pulses. After the programmed minimum update time
elapses and the next negative edge occurs, the unit saves the number of edges
that occurred during the elapsed time. The number of edges is multiplied by the
Rate Scale Factor, Rate Scale Multiplier, and the Rate Conversion Factor to
calculate the rate value. Averaging can be accomplished by programming the
Rate Minimum Update Time for the desired response. Extensive scaling
capabilities allow practically any desired reading at very slow count rates.
The following is a Block Diagram overview of the basic operation.