【正文】 n be done with high precision dualtrace Oscillographic, and to make the system Price increase. Minimum system circuit: the system to AT89C52 as the core. 20 keys from the keyboard posed by MM74C923 pleted its scan. Display System is the DCM162A, it is character LCD, there are two lines of 16, from 8bit characters in each line of five, because of its resolution is not high, difficult to display Chinese characters, so we use All English interface. In addition, the system also has 32 K of RAM (62256) and a 82 C55 port expansion as a backup. Part of the power system for the +5 V, +12 V and 12 V power supply three ways. Frequency Measurement modules: the use of SCM counter to measure the signal. Because the trigger pulse with the same input signal frequency, so just to trigger a pulse frequency can be measured. When the frequency of less than 5 Khz, the use of the method of measurement weeks, the measured signal to the gate for a period of time, the MCU to a machine cycle (1 us) for the benchmark time, that is, in its count cycle. When the input signal in the 5 K50K when measured by the frequency approach to the measured signal for the time benchmarks for the regular 1 S gate time, a timecount, that is, in frequency. Characters display module. The level of input in the Xaxis scanning signal, in Yaxis input field scanning signal, the Zaxis input signal brightness can be formed on the characters in the oscilloscope. The field scanning signals generated by the EPM7128 internal count. Zaxis data exist in the external ROM. Peak peak measurements: general AD (MAX197) on the importation of highspeed acquisition circuit to signal a longer time of sampling, get input signal to the maximum and minimum, and then their poor Value prior to passage by the decay times, you can get the input signal peaks peak. AUTOSCALE function: This feature automatically adjust to achieve the level of sensitivity and vertical sensitivity, so that waveform better be displayed. First, the system through the regular AD (MAX197) read as an input signal level trigger level so that the system is stable trigger. Then, call frequency measurement function, measured the frequency of input signal, because the level of sensitivity we will be divided into 20 us / div, , 2ms/div, 20ms/div, , in order to ensure that at least on the oscilloscope That a cycle of signal, so when the measured signal frequency f 5khz, with 20 us / div stall when the 500 hz， This system of measurement, the function and meet the targets were subject requirements. Completion of the functions are as follows: the input signal can be a single trigger, the trigger after the show that stability can not change with the input signal changes, the signal of a sampling of up to 2,048 sample points in a row could trigger mode of input signal sampling and realtime , And no significant wave distortion, the input signal is the exchange can also be a DC。 177。 12 accuracy。s configuration and procedures for the implementation of efficiency. The main function: DAQmx Read, Digital IIR Filter, Waveform Graphs, Write To Measurement File, Read To Measurement File, and other major function. Customizing the Waveform Graph The waveform graph indicator displays the two signals. To indicate which plot is the scaled signal and which is the simulated signal, you customize the plots. Complete the following steps to customize the appearance of an indicator on the front panel. 1. Move the cursor over the top of the plot legend on the waveform graph. Notice that while there are two plots on the graph, the plot legend displays only one plot. 2. When a doubleheaded arrow appears, shown in Figure 111, click and drag the border of the plot legend until the second plot name appears. Figure 111. Expanding a Plot Legend 3. Rightclick the waveform graph and select Properties from the shortcut menu to display the Graph Properties dialog box. 4. On the Plots tab, select Sawtooth from the pulldown menu. Click the Line Color color box to display the color picker. Select a new line color. 5. Select Sawtooth (Scaled) from the pulldown menu. 6. Place a checkmark in the Don’t use waveform names for plot names checkbox. 7. In the Name text box, delete the current label and change the name of this plot to Scaled Sawtooth. 8. Click the OK button to apply the current configuration and close the Graph Properties dialog box. Notice how the plot color on the front panel changes. 9. Experiment with other properties of the graph by using the Graph Properties dialog box. For example, try disabling the autoscale feature located on the Scales tab. 10. Click the Cancel button to avoid applying the changes you made while experimenting. If you want to keep the changes you made, click the OK button. 11. Save and close this VI. Saving Data when Prompted by a User Complete the following steps to build a VI that logs data to a file when the user clicks a button on the front panel. 1. On the block diagram, doubleclick the Write LabVIEW Measurement File Express VI to access the Configure Write LabVIEW Measurement File dialog box. 2. Change the file name to Selected in the File name text box to save the data to a different file. 3. Close the Configure Write LabVIEW Measurement File dialog box. 4. Rightclick the Signal input of the Write LabVIEW Measurement File Express VI. Select Insert Input/Output from the shortcut menu to insert the Comment input. 5. Rightclick the Comment input of the Write LabVIEW Measurement File Express VI. Select Select Input/Output187。 input signal frequency set at 10 khz, the level of the scanning speed in the 20 us / div , The oscilloscope show the 5 grid. Two measurements are also indicators of demand. (3) input noise measurements: the input termination, in