Design of high-precision time interval measurement module based on single-chip microcomputer

1 Introduction

Precision time interval measurement is a key technology in industrial, national defense and power applications. Pulse counting is the most basic method in time interval measurement technology [1]. Therefore, the study of time interval measurement technology based on pulse counting is of great practical significance. This paper designs a high-precision time interval measurement module and introduces the software and hardware implementation methods of the module. A large number of experiments have proved that this module can achieve accurate measurement of small time intervals and has high application value.

2 Principle Overview

The pulse counting method uses a standard signal to form a reference clock signal to be counted, with a period of Tref and a frequency of fref. By measuring the number n of reference clock signals within a time interval Δt, the value of Δt is directly displayed.

3 System Design

As shown in Figure 1, the system is mainly composed of high-frequency reference clock design, frequency division counting circuit, control panel and display circuit. The single-chip microcomputer realizes the software design of the functional initialization of each part. After the time measurement is completed, the frequency division counting result is read, and the time is calculated according to formula (1) and sent to the display circuit for display.

3.1 Hardware Design

It can be seen from formula (1) that high-frequency reference clock is the key to the time interval measurement of pulse counting method. In order to generate a high-frequency stable clock signal with low deviation and low jitter, this paper uses a high-stability temperature-compensated oscillator TC18B as the standard crystal input.

3.2 Software Design

The system software includes the initialization settings for each working circuit, and calculates the time interval Δt according to the n value obtained by the frequency division counting circuit, and sends it to the display circuit for display. The flow chart is shown in Figure 4.

4 Experimental Verification

The high-precision time interval measurement module developed in this paper is applied to the electromagnetic wave time domain reflection cable length measurement system. According to the electromagnetic wave time domain reflection length measurement principle, there is the following relationship:

In the equation, Δt is the time interval between the transmitted pulse and the reflected pulse, L is the cable length, and v is the propagation speed of the electromagnetic wave in the cable. For cables of specific materials, the wave speed takes a fixed value [2]. In this paper, v = 0.192 m/ns is taken.

It can be seen from equation (2) that for cables of known materials, the cable length L is proportional to the time interval Δt between the transmitted pulse and the reflected pulse. By measuring the time interval between the transmitted pulse and the reflected pulse of a cable of known length, the characteristics of the time interval measurement module can be verified. This paper conducts multiple measurements on cables of lengths of 7.01m, 66.77m and 120.30m, respectively. The measurement results are shown in Table 2.

It can be seen from the experimental results that the timing resolution of this module is 0.83ns, the measurement error is very small, and it can fully meet the requirements of high-precision time interval measurement.

5 Conclusion

This paper introduces a software and hardware design method for a high-precision time interval measurement module. The module has a simple structure, is easy to implement, and has high timing accuracy. It can not only accurately measure tiny time intervals, but also, based on the design of this module and combined with other technologies, it can measure time, frequency, and phase, which has high application value.

6 Innovations of this paper

This paper designs a high-precision time interval measurement module. This module phase-locks the standard crystal oscillator to output a 1200MHz high-frequency reference clock, and measures the number of high-frequency reference clocks in the time interval between the transmitted pulse and the reflected pulse to obtain the time interval Δt, with a timing resolution of 0.83ns.