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Weight Loading Dial Balance Helps Produce Thermoelectric Devices

A weight substitution dial balance is helping step up pilot production of thermoelectric materials at RCA’s Harrison, N. J. facility. The RCA Thermoelectric Engineering Products activity has built up over 3 years of experience producing materials and devices to convert heat into electricity through what is known as the Seebeck effect. This class of devices consists of an array of semiconductor elements which when heated at one end and cooled at the other generate electrical energy. The amounts of electricity capable of being generated in this fashion vary with the composition and size of the semiconductor elements. In recent years, this onetime laboratory curiosity has been turned into a working component of geophysical, military and aerospace equipment.

With this increased interest, attention has been focused on such semiconductor materials as silicon and germanium because of their stability and reliability in thermoelectric applications. It is in this field that the RCA engineers have established actual pilot production of devices being used on space programs, military systems and scientific installations. Such a device is currently circling the earth as part of the SNAP 10A system converting atomic energy to electrical energy.

In exploring methods of speeding up pilot production process, the RCA group became interested in overcoming the time disadvantage of having factory personnel manipulate tiny weights and conventional knife edge balances through the rub–her gloves of the controlled atmosphere box.

As many as 16 weighings per eight-hour shift are required to be made, and work includes as many as a dozen different formulations. Slowdown in the weighing made it difficult to maintain the production cycles the group sought to meet.

The equipment decided on was the DWL-2 made by the Torsion Balance Co., Clifton, N. J. It is a two-dial balance, one for weight substitutions (0 to 9 g) and one for fine weighing below 1 g. The balance requires no loose weights and has knobs large enough to be handled easily in a glove box.

The DWL-2 operates on a unique torsion principle that uses no knife edges to support the balance beam. It relies on a system of support yokes and  steel  torsion  bands  firmly  attached to the balance beam. In operation there is no friction and no wear but simply a flexing of the torsion bands. The gross weight is dialed directly with a centrally positioned dial, the fine weight by the turn of a smaller dial.

RCA engineers found the new unit to be fast, accurate and simple to operate within the glove box. The balance’s silicone fluid dash pot brings the unit to rest almost immediately and the dials can be manipulated without bringing the balance to rest. The DWL-2 has a capacity of 120 g making it suitable for the work it does at RCA where weighings range from 0.010 to 100 g. Its housing is ll 1/2 by 6 by 8 1/4 in., making it easy to fit in a glove box and still leave room for material containers and instruments.

An RCA technician uses a weight loading dial balance for careful production of charge quantities of raw materials used to manufacture reliable thermoelectric material and devices. The two-dial balance is made by the Torsion Balance Co.


Published in 1967