How the PLC analog input filter ten ways -

1, arithmetic average filtering method, A method: take N consecutive sampling value arithmetic average arithmetic for the larger the value of N: signal smoothness is higher, but lower sensitivity to the value of N is small: signal smoothness is low, but the sensitivity is higher value of N is: general flow, N = 12; Pressure: N = 4 b, advantages: suitable for general has random disturbance signal filtering, the characteristics of this signal is A average signal fluctuates up and down near A numerical range C, disadvantages: for measuring slower or request data computing fast real-time control is not applicable to compare waste RAM

2, median filtering method, A method: continuous sampling N times ( N take an odd number of) The NTH sampling values by the intermediate value of the effective value of size B, advantages: can effectively overcome the volatility of the interference caused by accidental factors of the change of the temperature, liquid level measured parameters have good filtering effect of slow C, disadvantages: should not be in a rapidly changing parameters such as flow, speed,

3, limiting filtering method ( Also known as judgment filtering method) A, method: according to experience, to determine the maximum deviation value of twice sampling allows ( As A) When every time A new value detected to determine: if the value and the last time the difference between the '= A, is the last time this value if the effective value and the difference between the values of A, then the value is invalid, give up this value, use the last value instead of the value of B, advantages: can effectively overcome the pulse interference caused by accidental factors C and disadvantages cannot restrain the periodic interference poor smoothness

4, median average filtering method ( Also known as pulse interference prevention average filtering method) A, methods: the equivalent of 'median filtering method' + 'arithmetic average filtering method' for sampling N data, take out A maximum and A minimum value and calculate N - Two data selection of arithmetic average value of N: 3 ~ 14 b, advantages: combines the advantages of two kinds of filtering method for occasional pulse interference, can eliminate the pulse interference caused by the sampling deviation of C, disadvantages: measurement speed is slow, and arithmetic average filtering method as wastes RAM

5, recursion average filtering method ( Also known as the moving average filtering method) A, method: take N consecutive samples values as A queue queue length of fixed N sampling to A new data into the next morning, and throw away the original team first data at A time. ( First in first out principle) N data arithmetic average operation in the queue, the selection of the value of N can obtain a new filtering results: flow, N = 12; Pressure: N = 4; Liquid level, N = 4 ~ 12; Temperature, N = 1 ~ 4 B, advantages: have good inhibitory effect of periodic interference, smoothness cross system used for the high frequency oscillation C, disadvantages: low sensitivity of occasional pulse interference inhibitory effect is bad is not easy to eliminate the sampling value deviation caused by pulse interference does not apply to pulse interference serious occasion wastes RAM

6, limiting average filtering method A and method: the equivalent of 'limiting filtering method' + 'recursion average filtering method' for each sample to the new data to limit processing first, and then into the queue for recursion average filtering processing, advantages: B combines the advantages of two kinds of filtering method for occasional pulse interference, can eliminate the pulse interference caused by the sampling deviation of C, disadvantages: more waste RAM

7, weighted recursive average filtering method A and method: is the improvement of recursion average filtering method, the data of different time different rights usually, the closer the now moment, right to obtain. Give new samples values of weight coefficient, the greater the sensitivity is higher, but the lower the signal smoothness, advantages: B applies to have larger pure lag time constant of the objects and sampling period is shorter system C, disadvantages: for pure delay time constant is lesser, sampling period is longer, change slow signal can't rapid response system is disturbed by the severity of the filtering effect is poor

8, first-order lag filtering method, A method: take A = 0 ~ 1 the filtering results = ( 1 - 一) * the sample B + a * last filtering results, advantages: to periodic interference has good inhibition is suitable for the higher C, disadvantages: the frequency of the wave phase lag, the degree of sensitivity low hysteresis depends on the size of a value not eliminate filter frequency higher than 1/2 of the sampling frequency jamming signal

9, eliminate shake filtering method, a method: setting up a filter for counter sampling value compared with the current effective value: if the sampling value = the current effective value, the counter reset if the sampling values the 'current RMS, counter + 1, and whether the counter maximum = N ( Overflow) If counter overflow, will be the value to replace the current RMS, and clear the counter B, advantages: to change the slow measured parameters has good filtering effect, can avoid repeated on/off near the critical value of the controller to beat or display numerical C jitter and disadvantages: for rapidly changing parameters should not be if in A sampling to overflow the counter value is interference value, will interfere with the value as A valid import system

10, limiting shake filtering method A and method: the elimination of 'limiting filtering method' + 'shake filtering elimination method' first clipping, after the shake B, advantages: inherited the 'limit' and 'shake' elimination of the advantages of improved 'shake filtering elimination method' of some defects, avoid interference values C, import system faults: the parameters of the unfavorable for quick change.