The invention relates to a control method of a rapid high-precision
cold mirror type
dew-point instrument. A
dew point chamber, a photoelectrical detecting
system, a refrigerating
system, a temperature measuring
system and a single-
chip microcomputer control
processing system are included. Composite control of two control
modes is adopted for the system. Firstly, a threshold value is set, and the system measures
light energy of reflected light of reaction
frost layer thickness in real time, calculates the difference value Rx of the current
light energy and a control target value and the change rate
delta Rx of the
light energy and carries out fuzzy
processing control if Rx is larger than the threshold value. Control
processing is carried out according to a proportional-integral (PI) control rule when the error Rx is smaller than the threshold value, working current is controlled to enable the light energy to reach the control target value, the change rate of the light energy is controlled within the allowable range, proportional-integral control is stopped, and a
dew point value is output. By means of fuzzy control, good transient performance can be obtained, the balance time of the system can be shortened, measurement can be accelerated, but an integration element is lacked, the system
static error cannot be eliminated, errors are caused by measurement, and proportional-integral control can eliminate the system
static error and improve precision. Thus, through
composite application of fuzzy control and proportional-integral control, the response speed of the system is increased, and the
measurement precision of the system is improved.