FPGA boosts position sensor performance

Paul Boughton

Lion Precision's new ECL202 eddy-current displacement/position sensor is said to benefit from significantly improved thermal stability and immunity to electromagnetic interference (EMI), as well as improved linearity and resolution.

The sensor employs FPGA technology, enabling complex, proprietary mathematical algorithms to achieve higher performance levels than purely analogue methods.

Don Martin, president of Lion Precision, comments: "Using FPGA digital processing techniques, we can achieve performance that simply is not possible with discrete analogue electronics."

Digital technology can very precisely detect the sensor's signal and more easily differentiate it from other electrical signals present in the sensing environment. This means the sensor continues to work well in electrically noisy environments such as near motor controllers or other high-power switching electronics. Using this same proprietary method, multiple ECL202 sensors can be positioned near each other without the mutual interference usually experienced with eddy-current sensors.

Internal calibration tables of tens of thousands of points assure precise linearity. Achieving these same levels of linearity with analogue circuitry often involves a trade-off between linearity and other performance parameters such as thermal stability or resolution. With digital technology, this trade-off is no longer required. The ECL202 sensor is maximised for all of these parameters. Digital circuitry is immune to drift associated with analogue circuitry, providing the ECL202 with greater thermal stability than analogue designs. The ECL202 also offers new features only available with digital technology: pushbutton offset adjustment, pushbutton setpoint adjustment, external offset and setpoint adjustments and user-selectable bandwidths.

The sensors are available in a choice of outputs (analogue 0-10V or digital setpoint switch closure) and with sensing ranges from 0.5-15mm. Resolution is as low as 0.008 per cent at 10kHz (dependent on the probe, range and bandwidth), and bandwidth is user-selectable (100Hz, 1kHz, 10kHz or 15kHz).