How a Capacitive Encoder Works

AMT absolute capacitive encoders consist of three basic parts as shown in the illustration above. The transmitter PCB emits an ac field that is distorted by the metal pattern on the rotor as it turns. A sinusoidal metal pattern on the rotor distorts the ac field in a way that is repeatable and predictable. This occurs as a result of varying capacitive reactance between the signal generated by the transmitter and the metal on the rotor. The field receiver uses the AMT ASIC to convert the modulated signal into digital position information, while the processor on the absolute encoder retrieves the position data from the ASIC and prepares it for export on the digital serial bus.

Benefits of Capacitive Technology

Thanks to its capacitive design, the AMT series is not susceptible to environmental contaminants such as dirt, dust and oil that would disable a typical optical encoder. Additional advantages include the lack of an LED which can eventually fail, a wider temperature range, higher vibration tolerances, and very low current consumption. The digital nature of the design also allows for increased flexibility through programmability of various features, ultimately reducing assembly time and cost compared to other encoders. And, compared to magnetic encoders typically valued for their rugged performance, the AMT series offers higher accuracy and stable performance under various temperature conditions.

Rugged

·         Not susceptible to airborne contaminants

·         No LEDs to fail

·         Far less susceptible to vibration due to rotor materials

Cost

·         Greatly reduced assembly time & cost

·         Lower price than most competitive offerings

Current Usage & Accuracy

·         Lower current consumption than competition

·         Higher accuracy than rugged counterparts