The system uses distributed control network, divided into upper and lower machine two parts, the host computer hardware, including CAN communications adapter and the host machine monitoring and management component; lower machine by the CAN nodes and in situ sensors group and the control of temperature and humidity parameters device component, shown in Figure 1.

By adjusting the Ral7, Ral8 and Ral9 size, get a larger resistance. However, the process of debugging, we have observed for the measurement time extension Shuchurengran Hui moved to saturation, for which we took advantage of a first-order part with Xiang Ji Fen out the output of the DC component, feedback to Ral9 the end, the formation of self Gensui Network , as shown in the left portion of Figure 2. Use to select the integration capacitor leakage current is relatively small, drift is small, relatively stable performance of the capacitor, the amplifier to select the high gain, high input impedance, low bias current, low drift operational amplifiers, can guarantee the performance of the charge amplifier.

In the application of active vibration control real interest to the signal frequencies are in between 0.5 ~ 200Hz, In order to filter low-frequency drift and unnecessary high-frequency signal, we design a five-order Bessel (Bessel) Di Tong Hu a first-order high-pass band-pass filter composed of five order Bessel low pass it by two second-order low-pass and a first-order low-pass form, their parameters are: passband gain of a cut-off frequency of 475Hz , Q value of 0.577; pass band gain of a cut-off frequency of 565Hz, Q values of O. 737; pass band gain of a cut-off frequency of 530Hz, one, two second-order low-pass circuit by the unity gain KRC. ??? Signal into the DSP's ADC should be preceded by the addition circuit to adjust the ratio to between 0 ~ 3V, 0V, or lower than 3V DSP have damaged the danger of this we have added a limit protection circuit

In this paper, MAX547 as the core component of the F2812 design and implementation of the D / A converter circuit. MAX547-house contains eight 13-bit voltage output D / A converters have an input before each DAC latch and the DAC latch, can be separately gated, to 8 D / A converter. Two DAC per share a reference voltage, a total of four independent external reference voltage. MAX547 interface signal has three address lines, respectively, eight-channel addressing options, 13-bit data line, a chip select / CS, Write / WR, asynchronous input / LD and clear / CLR and other control signals, control signals are level triggered. These interface signals are with the TTL / CMOS level matching, it directly with the MAX547 F2812 connected without the need for level translation. MAX547 is a ± 5V dual supply, the output voltage swing of -4.5 V ~ 4.5V. ??? When the MAX547's write signal / WR and the chip select signal / CS are low, and A0, A1, A2 Address signal is valid, the corresponding channel input latch open, read the conversion values from the data line , when / WR, and / CS goes high one, the data will be locked into the corresponding input latch. / LD is responsible for switching DAC latch, when the / LD is low, DAC latch open, the data from the input latch into the DAC latch, when the / LD becomes high, the data will be maintained in DAC Latch device, the count by the DAC to analog conversion. When / LD, / WR and / CS are low, the data can be directly transmitted to DAC latch, but the / LD should be higher than / WR high inversion delay 50ns. / CLR, you can convert the contents of the DAC is set to 1000H, AGND to the analog output voltage. ??? F2812 has the external interface (XINTF), can the image of five independent external storage space, each storage space has a chip select signal. 8 channels to MAX54.7 address assignment in an external storage area 0, through an external interface bus connection with the F2812 shown in Figure 4. To start the MAX547 internal DACA, DACB, DACC, DACD, DACE, DACF, DACG, DACH carry out a number - analog conversion, respectively, to address D9H, B2H, B3H, F4H, F5H, 7EH, 7FH write the data that need to be converted be. For MAX547AEQH need four independent reference voltage, the system uses a precision voltage reference provides a standard chip REF02 voltage, after four buffered voltage follower. REF02 5V output standard voltage, after conversion later, you can output the size of a standard adjustable voltage. Follower used MAX494, the PCB design, circuit lead to reduced interference, better to MAX494 OPAMP MAX547 input directly connected to the input reference voltage, shown in Figure 4. In addition to reduce the D / A converter ladder caused by high frequency wave