| 摘要 |
<p>An initial positive trigger value is above a minimum positive trigger value which is above an input signal DC component value. An initial negative trigger value is under a maximum negative trigger value which is under the input signal DC component value. Maximum and minimum signal values are measured and then they are used for the next positive and negative trigger value calculations. A positive signal half period is measured by measuring the time interval from the time point when a signal value becomes greater than the positive trigger value, to a time point where the input signal becomes less than the negative trigger value when the negative half period measuring starts. The negative half period measuring ends when the input signal value becomes greater than the positive trigger value. Positive and negative half period measurements are repeated several times and measured half periods are stored to memory. The difference of two different half period sums must be less than a given small value to accept one of two sums as N signal periods.</p> |
