Unique Technology

Unlike most laboratory balances, which employ magnetic force restoration as a weight sensing technology and unlike most counting scales which use strain gauge load cell technology. Setra Systems, uses a unique sensor of its own design. All Setra Balances & Scales use a high purity Alumina ceramic variable capacitance load cell.

The mechanical portion of the VCLS (Variable Capacitance Load Sensor) is a high purity alumina ceramic. Excessive shock loads are transferred to the housing through a system of fl exures and stops, making the scale very durable.

Two parallel gold plated bars are fused to the sensor’s ceramic beams. This creates a capacitor. The gap between the plates is only a few “mils” (thousands of an inch) thick. This capaci- tor is then connected into an electrical circuit to form an Inductive Capacitance Oscillator. With no load applied the oscillation frequency is approximately 10 megahertz.

As load is applied, the capacitor gap is slightly reduced (or, in some cases, opened) by an amount imperceptible to the naked eye. The capacitance changes with changes in the gap,and the oscillation frequency in the circuit also changes. From no load to full load (equal to scale capacity), the frequency changes by 2-3 megahertz, an amount proportional to the weight on the scale.

The scale’s microprocessor counts the oscillations in the circuit and converts the signal to weight units, making any necessary corrections for environmental factors such as temperature, linearizes the output, digitally fi lters the result to dampen out vibration, and reports the weight to the display and to the RS232 drive. Because the Setra scale’s microprocessor can detect changes of one cycle, the Setra scales’s “internal Resolution” (IR) can be as high as 1 in 2 or 3 million, although other factors sometimes reduce the resolution to 1 in a million or lower.

BL Series

Features   Applications High Accuracy and Resolution 1/500,000 Capacities from 100 gms to 5 Kg Readability from 1mg to 10 mg Overload Protection up to 10,000% Bi-directional RS232 Communications Ports One-year Carry In Limited Warranty Jewelry weighing Laboratory