text: fig1 and 2 are used to explain an automated analysis device ( not depicted in any more detail here ), which comprises a measurement system in which a photometer circles around a circular ring - shaped sample plate for receiving 125 cylindrical reaction vessels with a constant speed ( 2 hz ). fig1 schematically shows some of the 125 available receiving positions past which the photometer is guided . the physical reference location is formed from a stop for a fork light barrier ( 200 ) and it defines the reference point or the initial position , from which the measurement locations 1 - 125 are arranged at known distances . the known distance between the physical reference location and the first measurement location is indicated by a double - headed arrow . the measurement locations are situated within the receiving locations for the reaction vessels such that an optical property of a reaction preparation in a reaction vessel , which was introduced into the sample plate , can be measured . for the purposes of correctly detecting measured values , it is necessary to ensure that each measurement location is correctly retrieved during each revolution . in the case of a known , constant rotational speed , the individual measurement locations are determined by measuring time intervals relative to the physical reference location . the measured time intervals can then be associated with the measurement locations . however , the accuracy of determining the physical reference location is restricted by various factors , such as , e . g ., interference or noise in the photoelectric sensor signal or an insufficiently homogeneous movement of the photometer . determining the physical reference location imprecisely leads to an imprecise determination of the measurement locations in the subsequent revolution , which in turn has a reduced accuracy of the measured value detection as a consequence . this in turn can lead to completely invalid faulty measurements , reducing the throughput of the measurement system . in order to reduce such erroneous measurements , the automated analysis device described here has a digital integrated circuit in the form of an fpga , the partial function of which is configured as a phase locked loop which determines a virtual reference location . fig2 schematically shows the design of the phase locked loop , which was realized by programming an fpga . controlling elements are depicted by dashed lines . the input signal ( pulse_in ) for this arrangement is the physical reference signal , which is generated by the fork light barrier whenever the photometer passes the physical reference location of the measurement system . when the measurement system is started up , i . e ., when it is in the unlocked state , the phase detector ( phase detector , δφ ) initially establishes the time interval , i . e ., the period , between a first and a second physical reference signal by way of a counter , and the result ( period_in ) is provided to the loop filter ( lowpass filter ) for further processing . later , in the locked state of the phase locked loop (“ locked pll ”), the current phase deviation of the last physical reference signal from the pulse signal sequence ( pulse_feedback ) generated by the pulse generator ( pulse generator ) is established , and this result ( phase_in ) is also provided to the loop filter for further processing . the completion of the phase comparison and the establishment of the period duration ( period_in ) in the phase detector are signaled by the control signal phase_rdy . the loop filter calculates a mean value over n measured periods ( period_average ) of the physical reference signals in order thus to establish a mean period value and forward this to the pulse generator . furthermore , the loop filter forwards the current phase deviation multiplied by a predetermined correction factor ( phase_corr ) to the pulse generator . the completion of the mean value establishment over n measured periods in the loop filter is signaled by the control signal calc_rdy . the correction factor corresponds to the gain ( or damping ) with which the phase locked loop subsequently undertakes a phase correction . small correction factors bring about a sluggish system , in which the difference in the phase angle from the output pulse ( pulse_out ) to the input pulse ( pulse_in ) is only corrected slowly to zero . here , the filter effect is high , i . e ., the deflection of the individual pulses is small in terms of the temporal position thereof . large correction factors bring about a faster correction of the phase difference with , at the same time , a lower filter effect and therefore an increased pulse deflection . for the system realized here in practice , the correction factor was determined to be ½ 6 ( 0 . 015625 ) on the basis of simulations . the employed loop filter has the property of dynamically adapting the filter depth , i . e ., the filter depth n is continuously adapted as filter result when the measurement system is started up , starting with the result from initially one revolution , an averaged result from two revolutions , etc . in order to keep the switching outlay low when calculating the mean value , the dynamic mean value formation was restricted to n = 2 k , k = 0 , 1 , . . . 10 . as a result , the mean value formation can be carried out by a simple shift operation of the binary value . the pulse generator generates a pulse signal sequence in the locked state . the period of this pulse signal sequence corresponds to the mean value over n measured periods of the physical reference signals . the phase angle and therefore the exact pulse location likewise emerge from the previous pulse locations . a phase deviation from one revolution leads directly to a phase correction adjustable by way of the correction factor . for the purposes of monitoring the revolution duration , the time interval of the last pulses is forwarded to a superordinate computer ( period actual ). no phase angle between the pulse sequence of the actually measured physical reference signals and a pulse signal sequence generated by the pulse generator is known immediately after the measurement system is started up . therefore , the first pulses are derived directly from the actually measured physical reference signals ( pulse_in ) and forwarded to the output of the arrangement ( pulse_out ) and to the phase detector ( pulse_feedback ). the control signal phase_lock is switched on , i . e . the arrangement transitions into the locked state (“ locked pll ”), after the phase deviations established by the phase detector drop below a predetermined threshold over a number of measurements . as a result , the dynamic filtering of the low - pass filter is activated and the pulse generation in the pulse generator is switched over to the filtered pulse period and the phase correction . each pulse of the output pulse sequence ( pulse_out ) in the locked phase corresponds to the virtual reference location of the associated revolution . the output pulse sequence is forwarded to a superordinate calculation unit , which then determines the position of the measurement locations in the photometric measurement system on the basis of the virtual reference location .