Time interval counter is an essential time and frequency measuring instrument for metrology and testing units. Based on the verification regulation of counters, this paper mainly introduces the principles and verification methods.

The time interval counter is composed of an amplifying and shaping circuit, a time base circuit, a gate circuit, a logic control circuit, a frequency divider circuit, a data selection circuit, a carry acquisition circuit, a counter circuit, a latch decoding circuit, and a display circuit.

The working principle of the time interval counter is that the measured signal is processed by the amplifying and shaping circuit, and the output pulse counter can receive the same pulse signal format, and the frequency is the same as the measured signal.

The time interval counter is generally four keys. We can design and convert these four function keys. When you use counters, you need to set them up, because time counters are different from ordinary counters. Smart counters usually have memory functions, so after we use them, we'd better clear the data and reset them.

The metrological equipment for calibrating time interval counters includes reference frequency standard, frequency standard comparison system, synthetic signal generator, standard time interval generator and power meter, and the verification items are as follows:

The SYN3204 type rubidium atomic standard frequency source satisfies the requirement of reference frequency standard in the inspection regulations. The output signal frequency contains 5MHz, 10Mhz and so on. When there is no GPS signal, the accuracy of frequency is 24 hours, and the accuracy is less than 5E-11. After tracking GPS signal for 24 hours, the average value is less than 1E-12, which is better than the corresponding technical index of the frequency meter.

The SYN5609 type frequency stability tester is used to test the short interval stability and frequency accuracy of the time interval counter. In addition, in order to satisfy the requirements of the intermediate frequency standard comparison system, 5MHZ and 10MHZ can be input, the SYN3301 type high stability crystal oscillator can be used to complete the comparison uncertainty.

According to the requirements of the inspection regulations, the frequency range of the synthesized signal generator should meet the measurement range of the frequency counter, and the accuracy is better than one order of magnitude.The SYN5651 type signal generator is recommended. According to the regulation, the maximum allowable level error is + 0.5dB (0GHz~1GHz) and + 1dB (1GHz~18GHz).

The standard time interval generator recommends the use of SYN5612 type, single output single positive, negative pulse or positive and negative pulse train; two outputs a single positive, negative pulse or positive and negative pulse train.

The frequency range and level range of the power meter should meet the requirements of the inspection area and recommend Agilent's X11911AP power.

The SYN5636 type time interval counter is used as a high level counter. Because of its complete functions, better performance indicators, high accuracy and sensitivity and wide measuring range, it has won a good reputation. It is especially suitable for time and frequency measurement in the fields of research and Metrology such as aerospace, missiles, weapons and other fields such as time measurement and crystal oscillator, electronic components and so on.

The verification of time interval counters can refer to the specific method of general counter JJG349-2014 verification procedures.

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