Rosemount 8712 - Pulse Width

Reference Manual
00809-0100-4664, Rev BA
January 2010
4-21
Rosemount 8712
The best choice for this parameter depends upon the required resolution, the
number of digits in the totalizer, the extent of range required, and the
maximum counter external frequency.
NOTE
For totalizing on the LOI, ten digits are available.
Pulse Width
The factory default pulse width is 0.5 ms.
The width, or duration, of the pulse width can be adjusted to match the
requirements of different counters or controllers (see Figure 4-1 on
page 4-21). These are typically lower frequency applications (< 1000 Hz). The
transmitter will accept values from 0.1 ms to 650 ms.
For frequencies higher than 1000 Hz, it is recommended to set the pulse
mode to 50% duty cycle.
If the pulse width is set too wide (more than 1/2 the period of the pulse) the
transmitter will automatically default to a pulse width of 50% duty cycle.
Figure 4-1. Pulse Output
Example
If pulse width is set to 100 ms, the maximum output is 5 Hz; for a pulse width
of 0.5 ms, the maximum output would be 1000 Hz (at the maximum frequency
output there is a 50 percent duty cycle).
To achieve the greatest maximum frequency output, set the pulse width to the
lowest value that is consistent with the requirements of the pulse output
power source, pulse driven external totalizer, or other peripheral equipment.
Field Comm. 1, 4, 2, 2, 2
LOI Key AUX. FUNCTION
PULSE WIDTH MINIMUM PERIOD (50% duty cycle) MAXIMUM FREQUENCY
100 ms 200 ms
0.5 ms 1.0 ms
Pulse
Width
Period
OPEN
CLOSED
1 Cycle
200 mS
-------------------- 5 H z=
1 Cycle
1.0 mS
-------------------- 1000 Hz=