Rosemount 8712C - Pulse Width

Model 8712C/U/H Magnetic Flowmeter Transmitters
4-10
Pulse Width
The width, or duration, of the pulse width can be adjusted to match the
requirements of different counters or controllers
(see Figure 4-1).
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.
Example
The maximum flow rate is 1,000 gpm. Set the pulse output scaling such
that the transmitter outputs 1000 Hz at 1,000 gpm.
HART Fast Keys 1, 4, 3, 2, 2
LOI Key Aux. Function
Pulse
Width
Period
OPEN
CLOSED
PULSE WIDTH
MINIMUM PERIOD
(50% duty cycle)
MAXIMUM FREQUENCY
100 ms 200 ms
0.5 ms 1.0 ms
1Cycle
200 ms
--------------------5Hz=
1Cycle
1.0 ms
-------------------- 1000 Hz=
Pulse Scaling
Flow Rate (gpm)
(60 s/min)(Frequency)
------------------------------------------------------=
1,000 gpm
(60 s/min)(1000 Hz)
-------------------------------------------------=
Pulse Scaling 0.0167 gal/pulse=
1 Pulse 0.0167 gallon=