A pulse generator circuit provides output pulses that vary in frequency in accordance with a digital input word. An external source frequency produces a predetermined number of pulses over a fixed time interval with the pulse generator circuit selecting the desired number of pulses from those in this interval to provide at its output. Any number of the pulses between zero and the total number in the interval may be selected. To assure their distribution over the interval, the pulses are arranged to occur in sets with the pulses of a given set occurring in the middle of the pulses of another set in order to prevent the bunching of selected pulses into any part of the interval. The sum of the pulses in the combined sets then provides in accordance with the digital input word the desired frequency which ranges up to and includes the source frequency.
Disclosed is an absolute value comparator for comparing respective absolute values of sequentially applied two data. A decoder circuit sequentially converts the applied data into a plurality of bit signals in accordance with a predetermined rule. After a preceding conversion bit signal is once held in a register circuit, the held bit signal is inverted for each bit by an inversion circuit. Thus, a logic circuit receives a preceding inverted bit signal and a succeeding conversion bit signal and outputs an output signal B indicating the result of comparison. Since a full adder is unnecessary, a comparison between the absolute values of the applied data can be made at a high speed.
To acquire and record the variation of a value such as a pressure as a function of a parameter such as time in a sonde (10) lowered into a well (12), pressure measurements are made at equal time intervals, these measurements are digitized and entered in a nonvolatile memory selectively so as to maximize the accuracy of the pressure variation reading during the measurement period, while minimizing the memory volume necessary for this purpose. The selection of the acquired measurements for their recording comprises a data compression stage in which are eliminated the measurements which do not correspond to a variation in the slope of the pressure-versus-time curve greater than a predetermined threshold. The data compression is effected in a buffer memory in which each measurement has associated with it a deviation index indicative of the time interval separating this measurement from the following one in the buffer memory. This time interval amounts to a number of elementary time intervals which is always a power (n) of 2, n integer, and the exponent n is stored as the deviation index.
A method and mechanism for generating a clock signal with a relatively linear increase or decrease in clock frequency. A first clock signal is generated with a first frequency which is then used to generate a second clock signal with a second frequency. The second frequency is generated by dropping selected pulses of the first clock signal. Particular patterns of bits are stored in a storage element. Bits are then selected and conveyed from the storage element at a frequency determined by the first clock signal. The conveyed bits are used to construct the second clock signal. By selecting the particular pattern of bits selected and conveyed, the frequency of the second clock signal may be determined. Further, by changing the patterns of bits within the registers at selected times, the frequency of the second clock signal may be made to change in a relatively linear manner.
