5B35
GENERAL DESCRIPTION
includes common-mode rating of: 1500V rms between input
The 5B35 is a single-channel signal conditioning module that
amplifies, filters, isolates and protects a wide variety of four-wire
RTDs. The module provides a linearized, highly accurate output
of 0 to +5V.
and output and input and power; 250V rms between power and
output – no return path is required between the power and
signal output commons.
Filtering and Protection – An optimized five-pole Butterworth
filter (with a 4-Hz bandwidth) provides 116dB of normal-mode
rejection (noise on signal) at 60 Hz and 108 dB at 50 Hz. Output
noise is an exceptionally low 0.3 Mv p-p in a 100 kHz
Accurate and Stable Performance – The four-wire
configuration of the 5B35 supplies RTD excitation from a
precision, protected current source: two RTD wires carry the
excitation current and two wires serve as signal-input leads that
measure the voltage across the RTD. Because no excitation
current flows through the signal input leads, the length or
resistance of the leads creates little or no RTD measurement
error. A low-drift chopper-stabilized differential amplifier
allows use of very low excitation current to minimize error due
to RTD self heating. The amplifies low input offset drift of
+0.01oC/oC and gain drift of +30ppm/oC. Assure accuracy over
the full operating temperature range.
bandwidth and 6 mV p-p in a 5 MHz bandwidth.
The 5B35 protects the computer side from damage due to field-
side over-voltage faults. The module withstands 240V rms at
the input terminals without damage, thereby shielding the
internal computer-side circuitry from field-side over-voltage
conditions. In addition, the 5B35 is mix-and-match and hot
swappable with all other 5B Series modules, so can be inserted
or removed from any socket in the same backplane without
disrupting system power.
True Three-Port Isolation – The floating, differential input
circuit on the field side eliminates the need for any input
grounding. Signal and power isolation by transformer coupling
uses a proprietary modulation technique for linear, stable and
reliable performance. A demodulator on the computer side of
the signal transformer recovers the original signal, which is then
filtered and buffered to provide a low-noise, low-impedance
output signal. True three-port isolation (Input-Output-Power)
A series output switch eliminates the need for external
multiplexing in many applications. The switch is turned on by
an active-low enable input. If the switch is to be on at all times,
the enable-input should be grounded to power common as it is
on the 5B01 and 5B08 backplanes.
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Figure 2
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