Scaletron Industries, Ltd. (USA) - Scaletron Industries, Ltd., a manufacturer of corrosion resistant digital and mechanical scales, has developed a new 4-20 mA circuit board which can now be included in all Scaletron gas cabinet scales. The new board is engineered to send the scale signal directly to the main system control panel as opposed to a local display. The new 4-20 mA board features a simple 2-wire lead which integrates the scale with the main control system. This affords systems engineers a time-saving and economical means of incorporating additional scales into large, existing monitoring systems.

“In large sensor monitoring systems such as those used in pharmaceutical manufacturing and fire suppression, “said Edward Dougherty, President of Scaletron Industries, LTD, “there are many inputs and outputs which must be collectively monitored and controlled. In these types of systems, local displays for individual gas cabinet scales are not needed.” Dougherty said, “It is far more practical, and in many cases necessary, that the numerous scales, sensors, and other electronic equipment in large sensor loops are monitored from a central control panel enabling comprehensive system analysis and more targeted response to alerts.”

The Scaletron 4-20 mA board transmits the scale signal using current rather than voltage. The innate integrity of the current loop permits signal transmission over long distances, past the display to the main system indicator, without being affected by voltage fluctuations, resistance or electrical noise. The 4-20 mA current loop remains constant over the entire circuit. This means the main control center receives a strong, accurate signal from the scale load cell.

Dougherty explained that voltage flow will vary depending on wire size and length. In monitoring systems, relying on a voltage signal results in control errors as the signal fluctuates over distance. In the new Scaletron board, however, the current flowing through the system will always be exactly the same in all components of the circuit — even if voltage fluctuates.

The new Scaletron system is very economical when compared to indicators used for local displays. The 4-20 mA board module is mounted in the Scaletron scale base and needs only a 24V DC loop supply. When a gas cylinder is placed on the scale, the load cell registers as voltage the physical property of pressure on the scale base. The board converts the load cell voltage circuit to an electrical signal which is the 4-20 mA current. The board continually reads the circuit flow and adjusts output voltage accordingly to generate the voltage needed to produce a 20 mA current through the circuit.

Scaletron’s expertise derives from the company’s thirty years in designing and manufacturing scales for use in water and wastewater treatment applications. Scaletron scales feature complete corrosion resistance inside and out. Scale housings are stainless steel and the load cells are silicone coated for additional protection against moisture and other adverse weather conditions. Electronics are housed in NEMA 4X, UL-approved enclosures which are resistant to chemicals including ammonia, carbon dioxide, hydrogen chloride, liquefied chlorine, sulfur dioxide and other corrosive materials.