RESUMO
The nonplanar four-frequency differential laser gyro (NFFDLG, also called ZLG in the United States) has many advantages, such as the absence of mechanical noise, a whole solid state, high stability of scale factor, and no time delay. Because of its excellent performance, NFFDLG is currently the subject of research. In this paper, the error induced by the thermal relaxation effect is investigated both theoretically and experimentally, and some methods and conclusions that could restrain this error effectively are proposed. The experiment data confirm reliably that NFFDLG has a thermal relaxation effect error during overturning. At the same time, it is pointed out that the error can be minimized by reducing the stop interval. Furthermore, since the sum frequency could be affected more seriously by the overturning thermal relaxation effect than the difference frequency could, the former one can be used as one more sensitive condition in actual applications. As far as we know, the overturning thermal relaxation effect was first investigated in China, which is even not mentioned publicly.