Reference Manual
00809-0100-4148, Rev BA
July 2010
Rosemount 148
2-8
Lead wire resistance seen by the transmitter = 150 m × 2 wires ×
0.025
/m = 7.5
POWER SUPPLY
The power supplied to the transmitter should not drop below the transmitter
lift-off voltage of 12 V DC.
Surges/Transients
The transmitter will withstand electrical transients of the energy level
encountered in static discharges or induced switching transients. However,
high-energy transients, such as those induced in wiring from nearby
lightening strikes, welding, heavy electrical equipment, or switching gears,
can damage both the transmitter and the sensor. To protect against
high-energy transients, install the transmitter into a suitable connection head
with the Rosemount 470 Transient Protector. Refer to the Rosemount 470
Transient Protector Product Data Sheet (Document Number
00813-0100-4191) for further information.
Ground the Transmitter
The transmitter will operate with the current signal loop either floating or
grounded. However, the extra noise in floating systems affects many types of
readout devices. If the signal appears noisy or erratic, grounding the current
signal loop at a single point may solve the problem. The best place to ground
the loop is at the negative terminal of the power supply. Do not ground the
current signal loop at more than one point.
The transmitter is electrically isolated at 500 V AC rms (707 V DC) at 50/60
Hz, so the input circuit may also be grounded at any single point. When using
a grounded thermocouple, the grounded junction serves as this point.
NOTE
Do not ground the signal wire at both ends.
Basic error
7.5
0.00385
/
C
100
----------------------------------------------------------------------------------
19.5
C
=
=
Error due to amb. temp. var. of
25 °C
0.0039
/
C
25
C
7.5
0.00385
/
C
100
-------------------------------------------------------------------------------------------------------
1.9
C
=
=