Helipot

 

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tech helipot
Beckman Helipot used in the Tektronix 5A13N Differential Comparator oscilloscope plug-in module
Helipot model A
 Model A Beckman Helipot used in early Beckman pH meters and CO2 Detectors (and many other instruments)
CO2 helipot
Dual-ganged Beckman Helipot used in the Model 216B CO2 Detector

Variable rotary resistors were a common component in electrical devices, especially radios, from the beginning of the 20th century.  They typically had a rotation of from 90 to 270 degrees, enough variability to control the volume of a radio transmitter or receiver.  With the development of more elaborate electronic instrumentation, whether it is the Beckman PH meter or military radar (see military Helipot applications here), more controllable variability in the resistance of a potentiometer became necessary.  The development of a multi-turn variable resistor by Dr. Beckman, the Helipot is a direct result of that need.  Whether used as a stand-alone high-accuracy calibration standard or ganged together as a crucial component in a complex electronic instrument, the Helipot quickly became the industry standard in precision variable resistance.  However, the original Helipot variable resistors, starting with the Model A used in the early Beckman pH Meters, were wire-wound, hence prone to early failure, especially in long-wire high resistance values.  To increase the usability of the Helipot, Dr. Beckman developed Helipots with cermet resistance elements, cermet being a very homogeneous ceramic/metallic material, for which his patents are listed below those for the basic Helipot.

US Patent #2,454,986: Variable Resistance Device

US Patent #2,473,048: Variable Resistance Unit US

US Patent #3,326,720: Cermet Resistance Composition and Resistor

US Patent #3,416,960: Cermet Resistors, Their Composition and Method of Manufacture