Reference Manual
00809-0100-4664, Rev BA
January 2010
Rosemount 8712
4-20
Alarm Level
The alarm level allows you to drive the transmitter to preset values if an alarm
occurs. There are two options:
• Rosemount Alarm and Saturation Values
• NAMUR-Compliant Alarm and Saturation Levels
Pulse Output
Under this function the pulse output of the 8712 can be configured.
Pulse Scaling
Transmitter may be commanded to supply a specified frequency between 1
pulse/ day at 39.37 ft/sec (12 m/s) to 10,000 Hz at 1 ft/sec (0.3 m/s).
NOTE
Line size, special units, and density must be selected prior to configuration of
the Pulse Scaling factor.
The pulse output scaling equates one transistor switch closure pulse to a
selectable number of volume units. The volume unit used for scaling pulse
output is taken from the numerator of the configured flow units. For example,
if gal/min had been chosen when selecting the flow rate unit, the volume unit
displayed would be gallons.
NOTE
The pulse output scaling is designed to operate between 0 and 10,000 Hz.
The minimum conversion factor value is found by dividing the minimum span
(in units of volume per second) by 10,000 Hz.
When selecting pulse output scaling, remember that the maximum pulse rate
is 10,000 Hz. With the 110 percent overrange capability, the absolute limit is
11,000 Hz. For example, if you want the Rosemount 8712 to pulse every time
0.01 gallons pass through the sensor, and the flow rate is 10,000 gal/min, you
will exceed the 10,000 Hz full-scale limit:
Field Comm. 1, 4, 2, 1, 8
Table 4-1. Rosemount (Standard) Alarm and Saturation Values
Level 4-20 mA Saturation 4-20 mA Alarm
Low 3.9 mA 3.75 mA
High 20.8 mA 22.6 mA
Table 4-2. NAMUR-Compliant Alarm and Saturation Values
Level 4-20 mA Saturation 4-20 mA Alarm
Low 3.8 mA 3.5 mA
High 20.5 mA 22.6 mA
Field Comm. 1, 4, 2, 2
LOI Key AUX. FUNCTION
Field Comm. 1, 4, 2, 2, 1
LOI Key PULSE OUTPUT SCALING
10 000gal
1min
-----------------------------
60sec
1pulse
0.01gal
16666.7 Hz=
To Next Page
Loading...
