Design And Implementation Of Handheld Oxygen Monitor

Oxygen has been widely used in the medical, metallurgy and chemical industry and other fields. Oxygen concentration of these applications has strict requirements. To measure the oxygen concentration accurately and in a user-friendly way plays a significant role in the improvement of product quality and in the ensurance of manufacture environment safety.This paper presents an accurate hand-held oxygen concentration instrument. The hardware circuit is designed considering of its function, size, and cost. The following circuits are designed:a signal acquisition circuit, a constant-current source circuit, an A/ D converter circuit, a USB transmission circuit, a keyboard interface and a display interface circuits.The preamplifier and A/D converter are shared by temperature and oxygen concentration signal channel to make the circuit compact and to reduce its cost. Special operational amplifiers are chosen to reduce the signal drift in the acquisition process. An automatic zero adjustment circuit and a dynamic adjustment of amplification factor circuit are designed to improve the detection accuracy of different oxygen concentrations. A low-power 16-bit microcontroller msp430f449 is chosen to reduce its power consumption.In the software development aspect, the following algorithms are accomplished such as the temperature compensation algorithm, the demarcation algorithm and the linear fitting algorithm etc.and in the statistical survey data foundation, has carried on the error analysis and the software adjusts. For ease of the operation, has designed Chinese demonstration menu.This measuring appliance may under the keyboard control, realize to the oxygen concentration examination, the memory, the communication and the demarcation, the result can demonstrate on the lcd screen.The average accuracy is+/-0.5%. There are three measuring ranges:0.01-99.7%, 0.01-25%,0.01-5%. The power voltage is 9V. The operating current is 30-50mA.