数字计频器，可以自动转切换量程，量程分别为10.0~99.9Hz，0.10kHz~9.99kHz，10.0kHz~99.9kHz-Digital frequency counter, can automatically turn switch range, range were 10.0 ~ 99.9Hz, 0.10kHz ~ 9.99kHz, 10.0kHz ~ 99.9kHz