FIGURE 19 - uploaded by Michael Lombardi

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Frequency is the rate of occurrence of a repetitive event. If T is the period of a repetitive event, then the frequency f = 1/ T. The International System of Units (SI) states that the period should always be expressed in units of seconds (s), and the frequency should always be expressed in hertz (Hz). The frequency of electric signals often is mea...

## Citations

... The direct conversion of the NDC to a digital equivalent avoiding the implementation of an analog-to-digital converter is an important issue [23]. Since the time/frequency measurement using counting methods [24] results in an efficient time/frequency-to-digital conversion, DCSs based on the conversion of the NDC to time/frequency are of particular interest. Hence, the typical designs of the DCSs [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22] resulting in NDC-to-time/frequency-to-digital conversion will be briefly discussed as follows. ...

... for both C 1 < C 2 and C 1 > C 2 . According to (24), the relative error E R caused by the finite resolution of the control unit is increased with the decrease of the duration of the second phase T 2 . Hence, the relative error E R (24) is increased with the decrease of the absolute value of the NDC (1). ...

... However, the increase of the frequency f clk requires the increase of the single supply voltage V DD [29]. So, a larger resolution of the digital equivalent N 2 and a decrease in the relative error E R (24) can be achieved at the price of increased single supply voltage V DD . If the resolution of a single n-bit BC is not large enough, the problem can be solved by the implementation of the BC as two n-bit BCs connected in series (the MSB of first BC serves as the clock pulse of second BC). ...

A current-mode interface (CMI) with mixed single/dual slope integration (MSDSI) for differential capacitive sensors (DCSs) is presented in this article. The proposed design is based on the integration of the reference current flowing through the capacitors of the DCS. The integration of the capacitor of a smaller capacitance is performed with a dual slope. Contrary, the integration on the capacitor of a larger capacitance is performed with only one slope. The normalized differential capacitance (NDC) defined as the difference-to-sum ratio of the DCS capacitances is proportional to the duration of only one time interval which is digitized using the counting method. There is no need for postprocessing in the proposed NDC-to-time-to-digital conversion. It has been prototyped using discrete off-the-shelf components mounted on a printed circuit board, with a single supply voltage of 3.3 V. The measured NDC is in the range
$|\text {NDC}| < 0.612$
, with the constant sum of DCS capacitances of 970 pF. Achieved full-scale error is smaller than 0.3%, with a range of conversion speed from 1770 to 2755 NDC-to-time-to-digital conversions per second.

... Moreover, the known value of the RC time constant is of essential importance for the functioning of various circuits based on integrators with RC elements [active RC filters, oscillators, monostable multivibrators (MMs), single-slope integration analog-to-digital converters, and ramp-comparator (COMP) voltage-to-frequency converters]. Because the RC variable has a time dimension and the time interval measurement is based on the counting methods [19], the development of the RC-to-digital converters (RCDC) was self-imposed. Several methods of the RCDC design have been recognized so far. ...

... is the duration of the integration influenced by the offset voltage V OFFoa of the OA used (19). An approximation has been made in (20) Taking into account the offset voltage V OFFcomp of the COMP used, Fig. 4, the condition (2) becomes ...

An
RC
-to-digital converter (RCDC) for the measurement of the
RC
time constant of the resistor and capacitor connected in series is presented in this paper. A simple RCDC design insensitive to the parasitic capacitances is based on the single-slope integration. The output voltage of the integrator is linearly changed from half the value of the reference voltage to its final value. The
RC
time constant is equal to the duration of the single-slope integration, and is independent of any other parameter. The proposed RCDC has been prototyped using discrete off-the-shelf components mounted on a printed circuit board, with a single supply voltage of 2.7 V. Measurements have been performed for 36 different combinations of the resistors and capacitors connected in series, where the measured time constant is in the range 45.77 μs <
RC
< 2.32 ms, for three different reference voltages. Achieved relative error is smaller than 1.96 % for the largest reference voltage used.

... Crystal Oscillator data are non-stationary and therefore classical statistics as standard deviation and variance can not be used to calculate this parameter. In this case Allan deviation is used to estimate the stability of a crystal over a period of time [14] ...

... In this case, time interval measurements were carried out every 5 seconds. The confidence level (1σ) of the stability can be estimated as [14]: ...

First part of this paper presents an ocean bottom seismometers (OBS) designed and constructed for mid-term deployments in order to study the earth dynamics and internal structure. Many marine research institutes have developed such equipment, however there is no standard method for their characterization and calibration. The second part discusses the characterization tests based on the international standards carried out to present the specifications of the equipment built. Calibration of the constructed OBS is carried out through an oceanographic cruise using a widely used reference OBS. Data quality of the instruments is evaluated by direct inspection of the corresponding seismic record sections.

Within the FleetNet project an ad hoc radio network for intervehicle communications (IVC) and road telematics is being developed. For the air interface, the framework of the UMTS Terrestrial Radio Access time division duplex (UTRA TDD) standard has been selected as the most promising candidate. The requirements and challenges for synchronization in an ad hoc network with rapidly changing topology and high velocities are discussed. Solutions for synchronization in ad hoc networks based on UTRA TDD are proposed and evaluated by means of link-level simulations. The results indicate promising performance with only minor changes to the UTRA TDD standard specifications.