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Solve the interference frequency measurement circuit median filter

Sampling interval (and frequency cycle is an even multiple of the sampling period), then the zero position Xiaban Zhou equal number of samples. Even if the negative half-cycle AC signal clipping, the exchange of the zero line as the center of the Xia Banzhou sampling times are the same. 4, shown in Figure 4, in a sampling frequency interference cycle 12, corresponding to the sampling point a ~ a, can be seen that the sample 6 on Xiaban Zhou. Numerically on a sort of a get a new numerical sequence s, S, S ... ... S value of the new middle of the sequence s, s to the nearest exchange value of the zero line. If the negative half-cycle part of the clipping, that s> 0, ~ Uao = (S7 + S) / 2; even if the entire negative half cycle are clipping, s8 = O time, s and S is also closest to the average of the exchange over the zero line error 8a. ~ A/2xsin (27r / n) (I1 is the sampling frequency cycle times). Can be seen when a sampling frequency cycle, the number of n is large, in the worst case,[link widoczny dla zalogowanych], the sampling error value and the measured values will be very small. This sort of value method in the effective filter frequency interference signals at the same time it is natural to filter out the unexpected interference signals, because after the sort of interference due to sudden spikes sampled signal is routed to the queue values at both ends and natural discarded. Measurement circuit, not only in this way unipolar: Ken Yuan Ji Sheng Castle in Mexico! Yi Yu Tak ugly plastic sensor ◎ ◎ 1I8 imprison toilet Wang Mingying DS18B20 DALLAS semiconductor company in the United States may be the latest networking, in-line digital temperature sensor. DS18B20 the temperature sensor, A / D sensor, register, interface circuitry in a single chip, the appearance is very similar to ordinary plastic transistors can achieve direct digital output, test, and has strong control, transmission distance,[link widoczny dla zalogowanych], anti-interference ability , miniaturization, micro-power consumption, easy MCU or microprocessor and microcontroller for data exchange and so on. Many intelligent temperature sensor using synchronous serial bus technologies, such as: Microwire / Plus (NSC) all adopts a serial bus protocol, and DS18B20 uses a 1-Wire bus protocol. 1-Wire is a DALIJAS's proprietary technology, which uses a bi-directional signal line for signal transmission, the interface is simple, saving I / O lines, easy to expand and maintain. Because of these advantages, DS18B20 is widely used in fire, explosion and other single-point, multi-point testing occasions, especially for cotton, grain and other inflammable and explosive materials in the large-scale warehouse management. A, DS18B20 to the characteristics of a port for communication. Each DS18B20 has a unique serial number, the practical application does not require any external components to achieve temperature, a temperature range of 55oC-+125 oC, the precision error of ± 0.5c 【=. Temperature directly to the scene \Resolution digital thermometer, the user can select the range of 9-12, internal temperature,[link widoczny dla zalogowanych], the lower alarm settings. The user to set the alarm temperature is stored in EEPROM, is still preserved after power off. g star duo Figure 1DS18B2031, view maps and package bottom view of the second, DS18B20 the pin description table features three legs 1DS18B20 ~ I, DS18B20 DS18B20 used to use a Wi is 1 line agreement, the data in a data line two-way transmission,[link widoczny dla zalogowanych], but most of the SCM is concerned, a simple hardware does not support single-bus protocol, so we must use the software to simulate a single bus protocol timing, thus completing the DS18B20 chip access. DS18B20 in an I / O line to read and write data, therefore, read a simple and effective, but also for bipolar measurement circuit. IV summarizes the paper discusses the value of the two filtering methods, the average value method and the take in order to take the value method. These two features are filtering the signal sampling period, there are strict requirements that must be the frequency sampling period into an even multiple of cycles. Median filter to compare the two methods, the average value method in the needs and limiting the joint application of filtering to reduce the impact of unexpected interference, and its measurement in the unipolar circuit has some limitations. The sort filter method is simple and can burst interference signal filtering for unipolar and bipolar circuit, but its drawback is the need to retain all of the sampling frequency period compare and rank the value,[link widoczny dla zalogowanych], if the sampling frequency period when the number of more this sort and store the sample values will consume more resources, SCM application of limited resources is particularly problems that need attention. [On the Communications: Fluid Systems Engineering Design and Research Institute, Zhengzhou 450004]! 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