Interval counter

The interval counter is a measuring device used to measure the transit time using electromagnetic waves. Clock generator is a high-precision oscillator or resonant circuit that - depending on the application - works with an absolute limit deviation of up to 10 ⁻⁹ seconds or a relative limit deviation of up to 10 ⁻¹⁴ .

The earlier common quartz oscillators have been replaced by atomic or molecular oscillation processes for about two decades .

Two examples of the permissible measurement deviation :

• In 1 · 10 ⁻⁶  s (1 µs or a millionth of a second) light or a microwave travels 300 meters. In order to obtain a precise location better than 1 m with a GPS receiver or GPS-supported navigation instruments , the interval counter must therefore work with a resolution below 3 · 10 ⁻⁹  s, i.e. in the nanosecond (ns) range.
• In the GPS satellite system, the aim is currently to reduce the deviation to 10 ⁻¹⁵ . Such an oscillator would only show a deviation of 0.000 0003 seconds (0.3 µs) in a century.

In the medium accuracy class, the electronics industry has been offering various "(time) interval counters " and "frequency counters" for over 10 years, e . B. for laboratories or self-made measuring devices. Some of the more popular devices include:

• the Universal Time Interval Counter "HP 5370B" (time measurement single shot to 20 ps (0.02  ns ), frequency 11 digits up to 100 MHz up to 1 s, 0.1-0.01 ns)
• and the Universal Time Interval Counter "SR620" ( Stanford Research Systems ) with a limit deviation in the range of a few hundredths of a nanosecond.

If the requirements are not as high, the PC's processor cycles can be used, which can measure event points in rapid succession with deviations of up to around microseconds. For more precise time measurements using a computer, time-to-digital converters (TDC) are available for the range from 100 femtoseconds upwards .

In another context of measurement technology , the term interval counter is used in sports stopwatches (for example the Sporttimer Pro ), where it means counting individual stops. Two independently running timers alternate by means of an impulse or the push of a button, and each time the previously set interval counter is reduced by 1 and emits a signal (see lap time ). Some electricity meters also work with metering points on an interval basis.

See also

• Time measurement , frequency counter , time counter
• Torzeit , Starlette , LAGEOS , satellite geodesy
• electronic distance measurement , satellite laser ranging (SLR), pseudoranging
• Timing , interval switch , clock counter , frequency standard

literature

• P. Sperber: High Resolution Modulation Time Interval Counter . IAG's 12th International Workshop on Laser Ranging , Matera (Italy)

Web links

• HP-5370B Data Sheet (Precision Time-Interval Universal Counter) (PDF; 17 kB)
• Precision counter (Time interval counter) SR620 (Stanford)

Individual evidence

1. ↑ TDCs - Time-to-Digital Converters. ACAM, 2014, accessed December 3, 2015 .  
2. ↑ TDC7200 Time-to-Digital Converter for Time-of-Flight Applications in LIDAR, Magnetostrictive and Flow Meters. (PDF; 1.5 MB) Texas Instruments , August 2015, accessed on December 3, 2015 .