5B42

The 5B42 is a single-channel signal conditioning module that interfaces with two-wire transmitters, providing an isolated,regulated 20V supply voltage. The 5B42 filters and amplifies the 4-to-20 mA process-current input to produce an accurately scaled, low-noise low-impedance output of +1 to +5 V or +2 to +10 V.

True Three-Port Isolation The floating, differential input circuit of 5B42 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 of 5B42 (Input-Output-Power) includes common-mode ratings of 1500 V rms between input and output and input and power, 250V rms between power and output no return path is required between the power and signal output commons.

Accurate and Stable Performance The 5B42 maintains accuracy over  the wide operating temperature range of -40 to +85 through design for low parameter drift. This enables the 5B42 to provide output offset drift of only +5 uV/ and gain drift of just +25 ppm/

Why an Internal Current Sense Resistor? The 5B42 offers significant advantages over signal conditioners that require an external current sense resistor. First, an external resistor is not protected from accidental connection to a 240 V rms power line. Next, the external resistor tolerance must be added to the conditioners specified errors. In contrast, the 5B42 is calibrated and specified with its internal 25 sense resistor. Further, the 5B42 signal input, loop supply and the sense resistor are all protected against accidental application of excess voltages up to 240V rms. Finally, there is no need to install an external sense resistor on the backplane, but if one is installed it will not affect 5B42 performance.

Filtering and Protection The 5B42 contains an optimized five-pole low-pass filter with a -3 dB bandwidth at 100Hz that provides a low-overshoot step response and exceptionally low noise of 200 uV pk-pk in a 100kHz bandwidth. Attenuation (normal mode rejection) of 5B42 increases at a 90 dB/decade rate beyond 100 Hz.

The 5B42 protects the computer side from damage due to field-side over-voltage faults. The 5B42 withstands 240 V rms at the input terminals without damage, thereby shielding the internal computer-side circuitry from field-side over-voltage conditions. In addition, the 5B42 is mix-and-match and hotswappable with all other 5B Series modules, so can be inserted or removed from any socket in the same backplane without disrupting system power.
 
A series output switch of 5B42 eliminates the need for external multiplexing in many applications. The switch is turned on by an active-low enable input. If the switch of 5B42 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..