Miniature load cell for audio equipment

Rega choose Zemic Q70 for novel stylus tracking force scale

Variohm EuroSensor: Rega began designing and manufacturing audio equipment in 1973 and today, thanks to its obsession with innovation and the resurgence of interest for vinyl, is now the UK’s largest manufacturer of high-end turntables. Rega doesn’t just make excellent turntables, its range includes amplifiers, loudspeakers, CD players, cartridges and tone arms as well as many accessories that enhance the hi-fi experience for the discerning listener. Demonstrating its continuing role as a technological innovator, Rega will soon be launching a new accessory – a weighing scale that precisely measures stylus tracking force. With tone arm set-up critical to sound performance as well as stylus and record condition, Rega’s new Atlas Tracking Force Scale will confirm tone arm adjustment to 1/100th of a gram with a working range of 3.5 to 5 gm in a simple in-situ process. As an integral component for the scale, Rega chose the Zemic Q70 series miniature load cell, supplied and fully supported in the UK by Variohm EuroSensor.

Having identified that an accurate way to measure tracking force was desirable for the high-end audio market, Rega set out to design a scale that would be affordable and be able to be offered alongside the majority of its turntable range. 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 Q70 series miniature load sensor is available in five range options from 0 to 20 gm, up to 200 gm 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 2 to 5 V DC supply. Its high overload capability and compensated temperature range of -10⁰C to ~+40⁰C ensures consistency in measurement and high reliability for normal ambient temperature conditions.

Rega’s Atlas Tracking Force Scale packages the Q70 miniture load sensor in an attractive case that fits the contour of the record deck’s platen. The battery operated scale has a simple on/off button and a three segment digital display.

About Tracking Force

Ashton Wagner explains the importance of this critical measurement. "Tracking force is the amount of force with which a stylus on the end of a tonearm is pressed into a vinyl record.  This is usually set with the use of a counterweight on the other end of the arm.  Accurate tracking force is critical for several reasons.  First, if the pressure is too light the stylus will be unable to follow all of the undulations in the groove and will bounce around or skip, possibly damaging the record.  If the pressure is too heavy, excessive wear will also occur.  Also, with some cartridge designs because the stylus/cantilever/coil assembly is held in some kind of suspension the tracking force can affect the alignment of the magnet and coils.  This has an impact on various performance parameters of the cartridge, such as crosstalk and soundstaging."  For more information visit Rega’s website at www.rega.co.uk

Variohm EuroSensor designs, manufactures or sources a comprehensive range of sensor technologies for linear and rotary position, load, force, vibration and temperature measurement in demanding applications throughout industry, agriculture, construction, autosports, aerospace and research.

About Variohm EuroSensor:

Variohm EuroSensor is a manufacturer, distributor and supply chain partner providing complete sales and application support across a comprehensive range of position, force, pressure, load, and temperature sensor technologies - for demanding measurement applications across industry, construction, agriculture, motorsports, research and more.