Dual-channel pseudorandom sequence generator with precise time delay between its two channels

In this paper, a dual-channel pseudorandom sequence generator is presented for the calibration of cross correlators in flow metering. In the sequence generator, the two channels have completely identical hardware structures so that they generate two identical sequences of pseudorandom signals to simulate two signals obtained from the upstream and downstream sensors of a cross correlator, respectively. Special control strategies in both hardware and software have been implemented in such a way that the error of time delay between the two channels can be reduced to less than a microsecond. The shift frequency and sequence length of each sequence channel and the time delay between the two channels can be adjusted in wide ranges to satisfy various requirements. The instrument has been evaluated by using a digital oscilloscope. Results obtained show that the control accuracy of time delay is equal to or better than 0.015% when the time delay is 1 ms or longer. Comparison with two commercially available noise signal generators shows that the error of time delay of the new generator is much smaller than those of the other two.