COUNTING APPARATUS AND METHOD FOR FREQUENCY SAMPLING

摘要

Prior techniques for determining frequency by counting the cycles of an input signal suffer from the limitation that counts are frequently lost between sampling intervals. This limitation is overcome by the present invention that provides an apparatus and method for counting the number of cycles of a sensor signal (FS) and of a reference signal (FR) that occur during respective sensor and reference intervals associate with a sampling interval defined by a sample signal (SAMPLE). The sensor, reference and sample signals are received by gating circuit (30) that generates a sensor gate signal (GATES) and a reference gate signal (GATER), the sensor and reference gate signals respectively defining the sensor and reference intervals. The sensor interval begins and ends synchronously with respect to the sensor signal, and the reference interval begins and ends synchronously with respect to the reference signal. The sensor, reference and sampling intervals are approximately co-extensive with one another. The apparatus further comprises a sensor court circuit (32) and a reference count circuit (34). The sensor count circuit counts cycles of the sensor signal that occur during the sensor interval, and the reference count circuit counts cycles of the reference signal that occur during the reference interval.