Rockwell Automation 1734-IK Encoder/Counter Modules User Manual - Manual (Page 38)

Publication 1734-UM006B-EN-P - August 2005
3-6 Input and Output Data
Decimal Position (Configuration Word 3)
This byte changes the significant digits of the frequency or counter
display.
In the frequency modes (period/rate [5], rate measurement [7]) for
example, a -2 will move the decimal point left 2 places, dividing the
frequency value by 100, a +1 moves it right, multiplying by 10. The
firmware checks for placement to be in the range -4
≤ value ≤ +2. A
value outside the range will move the decimal point to the zero
position and assert the programming error (PE) bit. Moving the
decimal point to the left (negative), allows high frequencies,
commonly present in rate measurement mode, to fit within a single 16
bit word. Moving the decimal point to the right (positive), allows low
frequencies, commonly present in period and continuous rate modes,
to have resolution displayed to 0.1Hz and 0.01Hz. Frequencies should
be kept below 3.2kHz for 0.1Hz resolution and below 320Hz for
0.01Hz. Scalars of Z/128, Z/64, Z/32 and Z/16 should not be used
when positioning is applied. 0 is the default setting.
In the counter modes (counter [0], x1 encoder [1], x2 encoder [2], x4
encoder [4]), it attenuates the counter display, for example, 20 divides
count+1 by 20. The value may be in the range 0 < value
≤ 255. The
result of requesting a number other than 1 performs the function:
(COUNT + 1)/ATTENUATION. This is useful for scaling a large
counter value to a smaller 16 bit value or a percentage. One is the
default setting and zero reverts to 1 to prevent a divide by zero.
Word 4 is reserved.
Time Base and Gate Interval (Configuration Words 5 and 6)
The gate interval byte sets the counter’s gate intervall using the time
base setting (16-bit word 5) as its time unit. (its resolution is
determined by the time base). The actual gate interval is the product
of the time base and the gate interval (ex: 50ms gate interval may be
produced with a time base of 10 and a gate interval of 5 or a time
base of 50 and a gate interval of 1). The maximum value of the
product of time base x gate interval is 3 seconds. The gate interval
must be entered when rate measurement [7] configurations are used.
The maximum value is 200.