Dual-channel pseudo-random signal generator with precise control of time delay between channels

In this paper a dual-channel pseudo-random signal generator is presented for the calibration of cross-correlators such as cross-correlation-based flowmeters. In this signal generator, the two channels have completely identical hardware structures so that they generate two identical sequences of pseudo-random signals to simulate two signals obtained from the upstream and downstream sensors of a cross-correlator, respectively. Special control strategies both in hardware and software have been implemented in such a way that the control error of time delay between the two channels can be reduced to less than a microsecond. The shift frequency and sequence length of each signal channel and the time delay between the two channels can be adjusted in wide ranges to satisfy majority of practical requirements. The start/stop control of each channel of signal and adjustments of the above parameters are carried out by a micro-controller with a dedicated keyboard and an LED display. The instrument has been evaluated by using a digital storage oscilloscope (Tektronix TDS220). Results obtained show that the control precision of the time delay is better than 0.05% when the time delay is 1ms and over. Comparison with an E+H commercial noise signal generator and an MP noise generator shows that the error of the new generator is much smaller than those of the other two.