New Voltage Attenuator System for Interfacing High-Voltage Signals to A/D Systems

Dataforth Corporation, Tucson, Arizona announces the introduction of its new SCMVAS (Signal Conditioning Modular Voltage Attenuator System), an analog signal conditioning system which is designed to safely monitor and accurately measure voltage potentials up to 1200V peak-to-peak. These high-level voltages are typically found in industrial applications such as induction heaters or electric-motor drive controllers. The system reduces the input signal to a level suitable for interface to data acquisition systems, while at the same time providing various filter characteristics and 1500Vrms isolation.

The SCMVAS is comprised of either an 8 or 16-channel backpanel, two models of SCM5B signal conditioning modules, and various models of SCMVAS-Mxxx attenuator modules. For each channel of high-voltage analog input, an attenuator module, the SCMVAS-Mxxx, reduces the input signal to a low-level voltage, which is then connected to a high-input impedance Dataforth SCM5B signal conditioning module; the SCM5B31-21 or SCM5B41-21. The SCM5B module filters, isolates, and converts the input signal to a voltage output suitable for a PLC or an A/D converter in a data acquisition system. Signal filtering is accomplished with a six-pole filter internal to the SCM5B module. The SCM5B31-21 narrow bandwidth module has a cutoff frequency of 4Hz and provides 95dB of normal-mode-rejection at 60Hz and 90dB at 50Hz. The SCM5B41-21 widebandwidth module has a cutoff frequency of 10kHz, which is high enough to measure power line voltages and their associated harmonics. A 1500Vrms isolation barrier is provided by transformer coupling, using a proprietary technique to suppress transmission of common mode spikes or surges. The attenuator and signal conditioning modules have excellent stability over time and do not require re-calibration. Overall system accuracy is ±0.1%.

Six standard SCMVAS-Mxxx attenuator modules are offered with maximum voltage input ranges of ± 100V, ±200V, ±300V, ±400V, ±500V, and ±600V. Custom input ranges may be ordered. A pass-through module is also offered which allows any standard SCM5B module to be used on the SCMVAS backpanels. This feature allows connection on the same backpanel to other signal types such as thermocouple, RTD, strain-gage, or other.

Input signal connections to the attenuator modules are made using a pluggable terminal block for ease of system assembly and reconfiguration. For safety purposes, the terminal block has a cover over the screws and there are no exposed high voltage points on the SCMVAS-Mxxx module, SCM5B31-21 or SCM5B41-21 module, or the mounting backpanel.

The SCMVAS has two specially designed backpanels for mounting the attenuator and signal conditioning modules. The SCMVAS-PB8 high density, 8-channel backpanel can be panel mounted or DIN rail mounted and provides the conditioned output signal on screw terminal blocks. Jumpers are provided on each channel to optionally connect or isolate each module’s I/O Common from other channel’s I/O Common and/or Power Common. The SCMVAS-PB16 has 16 channels simultaneously available to high-speed data acquisition (ADC) boards through a 26-conductor ribbon cable. A 19-inch metal rack, the SCMXRK-002, is available for mounting the SCMVASPB8 or SCMVAS-PB16 backpanels.

Both storage and operating temperature range of the system is -40°C to +85°C with relative humidity levels up to 95% non-condensing. The system requires 5VDC power. The SCMVAS adds to the Company’s already extensive line of high performance industrial signal conditioning and isolation products and systems. Dataforth Corporation is a worldwide leader in the design and manufacture of signal conditioning and data communications products for industrial and institutional markets.

For additional information and pricing, call 800-444-7644 toll-free, or e-mail at sales@dataforth.com.

Original release: January 2000