7B33

Rev. 0 | Page 2 of 8

GENERAL DESCRIPTION

The 7B33 is a single-channel signal conditioning module that

interfaces, amplifies and filters unipolar voltage inputs and

provides a protected precision output of either +1 V to +5V or 0

V to +10 V. To measure a process current input, a plug-on 250Ω

current sensing resistor, Model AC1391, may be installed

directly on the 7B backplane, using available pin sockets. The

external current sense resistor allows the current loop to be

maintained even when the module is removed from the

backplane. Model 7B33 features a nonlinearity of +0.02%

maximum and an accuracy of +0.1% maximum (+0.01%

typical). To accurately measure low level signals in electrically

noisy environments, 1500 V rms of galvanic transformer-based

isolation with a common mode rejection (CMR) of 105 dB @

50/60 Hz is provided. Rated to operate with a nominal +24

VDC supply, Model 7B33 is mix-and-match and hot-swappable

with other 7B Series input modules, so it can be inserted or

removed from any socket in the same backplane without

disturbing system power.

The two input pins of Model 7B33 are fully protected up to 120

V rms line voltage. A one-pole 100 Hz filter preconditions the

input signal prior to amplification by a low drift input amplifier.

Amplitude modulation is used to implement transformer

isolation (1500 V rms input-to-output and power). Isolated

front-end circuitry power is supplied by a DC/DC converter.

The output section contains a two-pole low pass filter (-3 dB @

100 Hz), a buffer amplifier and a power oscillator. The two-pole

output filter and subsequent buffer ensures that a low noise, low

impedance (<1Ω) signal is available at the output to drive loads

of 2 kΩ minimum.

Figure 2