Ing. Vojtěch Vigner, Ph.D.

Článek popisuje inovovaný systém pro porovnávání stupnice UTC(FEL) generované cesiovými hodinami 5071A/001 v. č. 3519 v Laboratoři přesného času a frekvence FEL ČVUT (Praha 6, Dejvice) a národní časové stupnice UTC(TP) udržované v Laboratoři státního etalonu času a frekvence (Praha 8, Kobylisy). Původní systém využíval pro porovnávání metodu společných pozorování (Common-View) pomocí GNSS přijímačů GTR 51/55 a současně dvoucestnou metodu přenosu času po optických vláknech pomocí optoelektronických adaptérů MATRIX. Nová metoda porovnávání je založena na technologii White Rabbit, která je v časových laboratořích FEL ČVUT, ÚFE AV a CESNET předmětem výzkumu od roku 2019.

Článek seznamuje s řešením systému přenosu času po optických vláknech mezi Laboratoří přesného času a frekvence FEL ČVUT (Praha 6, Dejvice) a Laboratoří státního etalonu času a frekvence (Praha 8, Kobylisy).

Comparison of high-performance time scales generated by atomic clocks in laboratories of time and frequency metrology is usually performed by means of the Common View method. Laboratories are equipped with specialized GNSS receivers which measure the difference between a local time scale and a time scale of the selected satellite. Every receiver generates log files in CGGTTS data format to record measured differences. In order to calculate time differences recorded by two receivers, it is necessary to obtain these logs from both receivers and process them. This paper deals with automation and speeding up of these processes.

Presented standard is intended for use in time and frequency calibration laboratories as a source of UTC-synchronized time scale with high longterm stability or for clock synchronization in distributed systems and sensor networks. Similar device was utilized for measurement published in the report Evaluation of timing GPS receivers for industrial applications for the 12th IMEKO TC10Workshop.

Presented standard is intended for use in time and frequency calibration laboratories as a source of UTC-synchronized time scale with high longterm stability or for clock synchronization in distributed systems and sensor networks. Similar device was utilized for measurement published in the report Evaluation of timing GPS receivers for industrial applications for the 12th IMEKO TC10 Workshop.

The paper is focused on time base frequency measurement of high resolution digitizers with resolution up to 16 bits without an external output of the time base signal.

To increase the quality of synchronization in industrial distributed systems is a frequent demand at present. Node synchronization can be implemented in the Ethernet network using time protocols, e.g. IEEE 1588 Precise Time Protocol (PTP). However, active network components like switches and routers have negative influence on achieved accuracy of synchronization because they affect a packet delay variation in the network. To suppress this effect, special (but expensive) industrial switches, with a packet propagation delay correction, can be used. Another way using either low cost GPS receivers for synchronization of local clocks or a special timing for data transfer is described in the paper. It will allow a cheaper solution that preserves high quality of synchronization. Besides, a device for packet delay measurement (PTP tester) was designed and developed to be possible to evaluate the proposed methods.

Článek je zaměřen na problematiku měření frekvence časových základen digitalizátorů s rozlišením 12 až 16 bitů, které nemají vyveden signál časové základny na externí výstup.

Node synchronization can be implemented in an Ethernet network using time protocols; e.g. IEEE 1588 [1]. Active network components like switches and routers influence the accuracy of synchronization because they affect a packet delay variation in the network. Therefore, the delay is not constant and, as well, the delay in one direction is not equal to the delay in the opposite direction. This paper presents a low-cost device that can measure the packet delay with high accuracy in both communication directions and, at the same time, calculate network parameters including a packet delay variation, path asymmetry and dependency of the delay in opposite directions. The measurements can be used for the estimation of synchronization accuracy within the tested network. Some network elements have an unexpectedly large variability of path delays and large asymmetry. This behavior can be measured directly and therefore it is possible to eliminate these devices from the network. The results can be also used for the manual calibration of end nodes. It is not recommended, however, as it is vulnerable to network topology changes.

Node synchronization can be implemented in an Ethernet network using time protocols; e.g. IEEE 1588. Active network components like switches and routers influence a precision of the synchronization because they affect the packet delay in the network. Therefore, the delay is not constant and also the delay in one direction is not equal to the delay in the opposite direction. This paper presents a low-cost device that can precisely measure the packet delay in both communication directions and, at the same time, calculate network parameters; e.g. the packet delay variation, the path asymmetry and dependency of the delay in opposite directions. Measured values can be used to determine the usability of the network for the IEEE 1588 implementation and to predict the quality of the synchronization in a network. These measurements are important to achieve a precise synchronization in a low-cost network infrastructure.

Synchronization of measurement and control units (nodes) in large distributed systems is a common problem of industrial automation. Efficient solution is based on using local time bases controlled (synchronized) by timing GPS receivers. For their industrial application, sufficient accuracy and stability of generated synchronization pulses and an acceptable price are required. Modern timing receivers satisfy these requirements. This paper evaluates two GPS receivers suitable for industrial “online” applications, the uBlox LEA-6T and the Trimble ICM SMT, both priced under $100 USD.

In industrial applications is a demand for the highly reliable and synchronous distributed systems. The problem is that in those systems the nodes maintain their own time using local clocks. This behavior can be suppressed by synchronization of the individual nodes. It is more effective to use GPS for synchronization in large distributed systems. This paper deals with evaluation of reachable accuracy of synchronization within industrial distributed system using low-cost GPS receivers. Results of measurements using the uBlox LEA-6T GPS Receiver confirm achievable accuracy better than 15 ns in terms of an RMS value.

During prototyping of measurement instruments and other embedded devices, there is a need for communication protocol for that device. SCPI (Standard Commands for Programmable Instruments) is standardized, easy to use and text-based protocol. It is useful for an early development of the device, because there is no need for a special client application. It can be also used as a final protocol of the resulting measurement instrument. This paper presents a SCPI parser library that can be used as a base for measuring device. User defines only the list of supported commands and implements functions for selected communication interface.

The synchronization of large systems is important for recording of dynamic actions and data acquisition of physical quantities over a wide geographical area. The chapter deals with synchronization of distributed measurement systems, especially synchronization using PTP (Precise Time Protocol, IEEE 1588). A practical case study presents a Master Clock module synchronized by GPS receiver. This module works as a high quality time base for PTP based system.

This paper describes the design of a development board for precise time scale preservation and the events time stamping. The board will be used for designing algorithms and methods of time and frequency calibration. During the development great emphasis was placed on the highest possible accuracy and while preserving low cost.

This paper describes the design of a device for precise time scale generation (tied to UTC) and the identification of time events. During the development great emphasis was placed on the highest possible accuracy while preserving low cost.