xLadder user manual-V2.0.0.6

Mathematical formula of PID loop instruction:

M n = MP n + MI n + MD n

M n : Output value

MP n : Proportion term

MI n : Integral term

MD n : Differential term

Proportion term

MP n = K c * (SP n - PV n )

MP n : Proportion term

K c : gain

SP n : Set point

PV n : Process quantity

Integral term:

MI n = K c * T s / T I * (SP n - PV n ) + MI n-1

MI n : Integral term

K c : gain

T s : Sampling time

T I : Integral time

SP n : Set point

PV n : Process quantity

MI n-1 : Last time integral term

Differential term:

MD n = K c * T D / T s * (PV n-1 - PV n )

MD n : Differential term

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