Emerson Rosemount 1152 Alphaline, Справочное руководство

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Reference Manual
00809-0100-4235, Rev BA
April 2007
2-7
Rosemount 1152
Figure 2-4. Transmitter Wiring
Connections.
Figure 2-5. Supply Voltage vs.
Load Relationship.
The capacitance sensing element uses alternating current to generate a
capacitance signal. This alternating current is developed in an oscillator circuit
with a frequency of 32,000 ± 10,000 Hz. This 32,000 Hz signal is
capacitor-coupled to the transmitter case ground through the sensing
element. Because of this coupling, a voltage may be imposed across the load,
depending on choice of grounding.
This impressed voltage, which is seen as high frequency noise, has no effect
on most instruments. Computers with short sampling times in a circuit where
the negative transmitter terminal is grounded detect a significant noise signal.
Filter this signal out by using a large capacitor (1
µ
f) or a 32,000 Hz LC filter
across the load. Signal loops grounded at any other point are negligibly
affected by this noise and do not need filtering.
Power
Supply
Terminal Side
(cover removed)
- + - +
- +
+ -
Design Region
Load (
⍀
)
12 20 30 40 45
0
1650
1500
1000
500
Power Supply (V dc)
4–20 mA dc
Design Region
Load (
⍀
)
Power Supply (V dc)
0
1100
1000
500
30 40 50 60 70 80 85
10–50 mA dc
1152-1152BG05A