Research And Development Of Dual-Channel Two-Dimensional Water Turbidity Detection Device

With the development of optoelectronic components and the improvement of computing speed of CPU chips,water turbidity detection equipments are upgrading rapidly.Nowadays most of manufactures apply optoelectronic components as sensors,obtaining water turbidity detection devices with better repeatability and better accuracy.However,optical receiving component is likely to be interrupted by external light source,such as environment light or bulbs.Therefor it exists uncertainty in the detection process.First ly,based on the underwater features of transmitt ing light and scattering light,transmitt ing-scattering D value vs turbidit y module was put forward as a plan to detect water turbidit y.Then the structure of turbidit y detection sensor was researched and designed: dual-channel two-dimensio nal structure.It facilitates sampling 3 groups of light signals in two dimensio n s,so SNR(signal to noise rat io)is improved.Meanwhile,LEDs are controlled by PWM,separat ing transmitt ing light,scattering light and back-ground light,also providing a preparat ion to eliminate the interruption that signal contains fro m back-ground light source.Next the back-ground light eliminat ing circuit was proposed.Today primary means o f avoiding back-ground light are to install an ant i-light detection space,then analyze water in the ant i-light space after it was sampled by water pump or other devices.Hence,turbidit y detectio n devices are more expensive and co mplex.Combining wit h switch controlling sequence and LED modulat ion,back-ground light eliminat ing circuit could creatively so lve the interruption problems that optoelectronic devices receive in a way o f circuit,co mplexit y and cost are tremendously reduced.Via zerocalibrat ion circuit,detection scale are extended.Besides amplifier and filter circuit module,IIR digital filter based o n Chebyshev theory was introduced and designed after we had compared filtering result s amo ng mult iple so lut ions.Experiments prove that Chebyshev digital filter is capable o f eliminat ing no ise and ripple in the effect ive wave,realizing the improvement of precisio n and reso lut ion.At last based o n theoretical analyzing of D-value vs turbidit y model,calibrat ion tests verified practicabilit y o f it.Test result shows the turbidit y detect ion device could reach 0.5% precisio n and has excellent repeatabilit y,meet ing the designed requirements.