- Interfaces to 100 Ohm Thru 10 kOhm, Full-Bridge, Half-Bridge, or Quarter-Bridge Strain Gages
- High-Level Voltage Output
- 1500Vrms Transformer Isolation
- ANSI/IEEE C37.90.1 Transient Protection
- Input Protected to 240VAC Continuous
- Fully Isolated Excitation Supply
- 160dB CMR
- 4Hz Signal Bandwidth
- ATEX Compliant
The SCM5B38 voltage input module provides a differential, isolated, analog input channel that is filtered, isolated, amplified, and converted to an analog output voltage. This voltage output is switchable via a logic input, allowing multiple of these modules to share a common analog bus without the need for external multiplexers.
In addition to the input, the output of the module is also galvanically isolated from the module supply. The galvanic isolation provides additional safety in industrial applications and reliably protects the downstream evaluation electronics. The SCM5B38 can interface to full-bridge or half-bridge transducers with a nominal resistance of 100 Ohm to 10 kOhm. A matched pair of bridge-completion resistors (to ±1mV at +10V excitation) allows use of low cost half-bridge or quarter-bridge transducers.
Strain gage excitation is provided from the module by a very stable 10V or 3.333V source. The excitation supply is fully isolated, allowing the amplifier inputs to operate over the full range of the excitation voltage. This feature offers significant flexibility in real world applications. Full scale sensitivities of 2mV/V, 3mV/V or 10mV/V are offered as standard. With 10V excitation, this results in ±20mV, ±30mV or ±100mV full scale input range producing ± 5V full scale output. Signal filtering is provided by a six-pole filter that offers 95dB suppression at 60Hz and 90dB at 50Hz. Two poles of this filter are located on the field side of the isolation barrier, the other four on the output side.
After upstream field-side filtering, the input signal is chopped by a proprietary chopper circuit. Isolation is provided by a signal transformer, with a proprietary technique for suppressing transmission of common-mode spikes or surges. The module is powered from +5VDC, ±5%. A special input circuit on the SCM5B38 modules provides protection against accidental connection of power-line voltages up to 240VAC.