Rosemount 848T, Справочное руководство

Страница: 29 / 60

Reference Manual
00809-0100-4848, Rev AA
July 2009
3-9
Rosemount 848T Wireless
Figure 3-9. 848T Wireless
Terminal Diagram
NOTICE
For a device to be Intrinsically Safe, it must operate on only one power
source. By converting a 4 – 20 mA signal to a measurable millivolt signal, it is
considered as a second power source in the terminal block of the 848T, and
voids the Intrinsically Safe approval. This does not affect the division 2,
non-incendive approvals so this configuration can still be installed and
operated in division 2 areas. Also, this technique should not be applied to a
4 – 20 mA device currently connected to a loop control.
The mA signal should not be directly applied to the transmitter's millivolt
terminals. Doing this without the resistor may damage the electronics. The
voltage applied across the terminals should not exceed 100 mV. Excessive
voltage could damage the transmitter.
Using the 375 Communicator or AMS, reconfigure the 848T sensor type to
either 4 – 20 mA (Rosemount), 4 –20 mA (NAMUR), or mV. The engineering
units are user-selectable and can be either mA or mV. Table 3-2 shows the
saturation and alarm thresholds for 4–20 mA (Rosemount) sensor type and
Table 3-3 shows the saturation and alarm thresholds for 4– 20 mA (NAMUR)
sensor type.
Table 3-2. 4-20 mA
(Rosemount) Saturation and
Alarm
Table 3-3. 4-20 mA (Namur)
Saturation and Alarm
4 – 20 mA
Device
Power
Supply
+
+
-
-
5 Ohm
Transmitter Status Analog Input (mA) Measured Voltage (mV) Analog Region
Sensor Saturation >21.71 >108.55 Upper Alarm
Sensor Out of Limits 20.8 – 21.71 104 – 108.55 Upper Saturation
Good 3.9 – 20.8 19.5 – 104 Normal Region
Sensor Out of Limits 3.79 – 3.9 18.95 – 19.5 Lower Saturation
Sensor Saturation <3.79 <18.95 Lower Alarm
Transmitter Status Analog Input (mA) Measured Voltage (mV) Analog Region
Sensor Saturation >20.96 >104.8 Upper Alarm
Sensor Out of Limits 20.5 – 20.96 102.5 – 104.8 Upper Saturation
Good 3.8 – 20.5 19 – 102.5 Normal Region
Sensor Out of Limits 3.64 – 3.8 18.2 – 19 Lower Saturation
Sensor Saturation <3.64 <18.2 Lower Alarm