Miniature load cell offers excellent durability and a scale that doesn’t require calibration by the user

Rega chose the Zemic Q70 series miniature load cell, supplied in the UK by Variohm EuroSensor for its new weighing scale that precisely measures stylus tracking force in its hi-fi turntables. Rega design engineer, Ashton Wagner explains how the project developed, "We looked for a load cell with an accuracy to one hundredth of a gram that would fully maintain that accuracy over its lifetime; we needed excellent durability and a scale that would not require calibration by the user." Budget constraints were also fully considered at the outset, "To meet our target costs the use of premium digital and analogue electronics were off the table. A microcontroller with an embedded commodity ADC was chosen which meant, that to achieve the accuracy we desired, we would have to use a high gain amplification circuit with little room for adjustment. We needed a gauge that would maintain consistent performance under variance in temperature, age, stress, and from gauge to gauge as well – after technical support from Variohm and thorough testing we thus chose the Zemic Q70 series load cell." The series miniature load sensor is available in five range options from 0gm to 20gm, up to 200gm and is well proven in hand-held scale applications. Its semiconductor strain gauge sensing element provides a 0.05% accuracy class and an output sensitivity of 0.5 +/- 0.15 mV/V for excitation from 2VDC to 5VDC supply. Its high overload capability and compensated temperature range of -10C to +40C ensures consistency in measurement and high reliability for normal ambient temperature conditions.