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The Finnish realization of coordinated universal time, designated UTC(MIKE), is derived from a single active hydrogen maser at the Centre for Metrology and Accreditation (MIKES). The frequency of a hydrogen maser typically drifts with time, leading to an approximately parabolic phase shift. At MIKES, a programmable delay generator is used to negate the phase drift of the maser. An improved control...
Fundamental metrology is closely linked to the development of science and needs good facilities to achieve low measurement uncertainty in demanding experiments. The laboratories must have good temperature stability, low vibration level, good electromagnetic shielding, clean room air, and humidity control. This paper outlines specification and design principles of a compact laboratory building that...
This paper gives a survey of the performance of existing current shunts designed by National Metrology Institutes (NMI's) around Europe. Key characteristics for power measurement; phase displacement, ac-dc transfer difference and power coefficient of the shunt resistance is reported for 5A, 50 A and 100 A shunts.
Local time in the Centre for Metrology and Accreditation is derived from our master clock, a hydrogen maser. An often occurring phenomenon in hydrogen masers is a small, approximately constant frequency drift. As a consequence, the time error of a hydrogen maser typically follows a parabola. To compensate for this, a programmable delay generator is used to produce an opposite function. Thus, a local...
In Nordic and Baltic countries there are several national and other time & frequency laboratories having atomic clocks. The accuracy ot the time is mostly based on factory calibrated GPS receivers without knowledge on the effect of local cabling and other delays. Thus the time error could easily be 10 ns or more. To improve the situation, an Euromet project 860 was started. At the same time an...
The most important feature of GPS-receivers in time keeping is long-term phase stability and reliability. MIKES and Nokia have studied in cooperation the performance of medium price commercial GPS receivers both in the short term and long-term sense. By comparing time differences of the receivers, both short term and long-term stability can be evaluated assuming that all receivers do not drift into...
A square-wave based AC Josephson apparatus is under development at MIKES. A new high-resolution custom made sine wave source has been developed and is being tested. A simple scheme for calibration of thermal converters (TC) with an AC Josephson system is suggested.
We studied how to control the frequencies of those simple crystals used in typical telecommunication transmitter. According to the common standards, the uncertainty of carrier frequency should be less than 0.3 ppm. That of simple XO is only 100 ppm. Two approaches have been studied here. The first one is the German transmitter DCF 77. The second one is the utilization of the NTP-time servers. We studied...
A significant challenge has been existed concerning the relationship between the manufacturing costs and the high performance of the handheld GNSS terminals. The crystals of the oscillators represent one the most expensive component in the terminals even, the crystals used in them, can often be called rubbish ones. The work is pending to develop a method including a mathematical / software procedure...
Timing performances of conventional coaxial cables like RG 223 and RG 58 were studied. The effects of timing pulse shape, cable bandwidth, ambient fluctuations and physical stress were as input parameters. Pulse delays and shapes were studied using a time interval counter and a fast digital oscilloscope. Delay as a function of frequency was studied with resonance method and phase delay measurements...
Long-term phase stability of GPS receivers is important in time-keeping applications. MIKES and Nokia Mobile Phones have studied in co-operation the performance of medium price commercial GPS receivers both in the short term and long-term sense. MIKES has run five GPS receivers of two manufacturers for over five years. An automatic measurement system has collected data from those receivers and from...
The Finnish Centre for Metrology and Accreditation (MIKES) has two HP 5071A Cs-beam standards (standard version from 1997 and high stability version from 2000) and one CH1-76 Passive hydrogen maser (since February 2003). A special four-channel phase comparator with better than 0.3 ps single shot resolution is used to study the short-term stability of the Cs-standards, with hydrogen maser as a reference...
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