Emerson Rosemount 1154DH, Справочное руководство

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Reference Manual
00809-0100-4631, Rev BA
April 2007
2-5
Rosemount 1154 Series H
Signal wiring need not be shielded, but twisted pairs should be used for best
results. In electrically noisy environments, shielded cable should be used for
best results. Do not run signal wiring in conduit or open trays with power
wiring, nor near heavy electrical equipment. Signal wiring may be ungrounded
(floating) or grounded at any place in the signal loop. The transmitter case
may be grounded or ungrounded.
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 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, will have no
effect on most instruments. Computers with short sampling times in a circuit
where the negative transmitter terminal is grounded, will detect a significant
noise signal. Filter this noise with a large capacitor (1 µf) or by using 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.
Figure 2-2. Transmitter Wiring
Connections.
Figure 2-3. Transmitter Load
Limits.
Terminal Side
(cover removed)
Power
Supply
12 35 40 45
0
1825
1500
1000
500
Power Supply (V dc)
0
13.5
Design
Region
Qualified
Region
50
1575
Load
Resistance (
)
4–20 mA dc
1154-G05A