Automatic range control in DNA electrochemical signal acquisition instrument (1)

DNA electrochemical signal acquisition instrument is based on electrochemical analysis design of diagnostic instruments.

Electrochemical analysis technology is the determination of DNA sequences, it is relative to the surface analysis techniques, gel electrophoresis, microcalorimetry, capillary electrophoresis, electrochemical analysis techniques and analysis technology, etc. larger advantage. This design uses voltammetric detection of DNA and biochemical responses to current acute promyelocytic leukemia (APL) and chronic myelogenous leukemia (CML slower seed) to early diagnosis. Acquisition instrument has a compact, integrated and in situ, in vivo, real-time, online test, etc.

Electrochemical methods of detection system normally three-electrode system: working electrode for gold electrodes, which fixed a DNA fragments and for detection of electrically active hybrid indicator; reference electrode is a silver/silver chloride electrode; auxiliary electrode for Platinum electrodes.

In General, use CHI660C and select cyclic voltammetry do electrochemical experiments, you set its sensitivity, once the sensitivity settings not appropriate, it will affect the test results.

Therefore, in order to improve the current signal detection accuracy, DNA electrochemical signal acquisition instrument requires auto sensitivity control function.

This paper first outlines the self-made DNA electrochemical signal acquisition instrument of the overall framework, the functions and properties, and then elaborated on the automatic range control system signal acquisition module application, and provides the appropriate hardware and software design.

1 system design

The entire DNA electrochemical signal acquisition unit mainly consists of four modules, as shown in Figure 1.

Processor module this partly by TI's DSP processor TMS320F2806, mainly responsible for signal generation modules and signal acquisition module for control, at the same time, the acquisition of the signal is processed, and sent to the host computer.

Signal generation module includes 16-bit D/A, low-pass filter and potentiostat.

The module in the DSP control, depending on the choice of electrochemical detection method, producing the corresponding waveform signal.

Signal acquisition module includes I/V conversion circuit, automatic range control circuits, voltage regulator circuit, low-pass filter and 16-bit A/D.

Its function is to capture the current pool of electro-chemical reaction.

Electrochemical reaction pool module for the three-electrode system provide places of electrochemical reaction, reaction in the current signal to the signal acquisition module.

2 automatic range control system design

2.1 automatic range control system design requirements

Taking into account the General electrochemical reaction current signal range 1.0 × 10-7-1.0 × 10-3A, therefore requires DNA electrochemical signal acquisition instrument signal acquisition part of circuit can detect the range of the current signal and stronger anti-interference, noise and signal distortion.

In addition, the signal circuit also need fast and accurate with CNC-diaodang capabilities under certain conditions and automatically adjusts sensitivity, that is, automatic l stalls or falling.

In General, you should make the converted amount in A/D conversion linear zone, as analog in 1/2 full degree ~ close to full degree area conversion, that is, according to the unknown parameters of the range of values, select the appropriate sensitivity automatically.

2.2 automatic range control system design