Basic composition of the instrument and how to use it

In simulation experiments, commonly used electronic instruments include function signal generators, DC voltage regulators, AC millivoltmeters, and frequency meters. Together with the multimeter, they can complete the test of static and dynamic working conditions of analog circuits.

Various electronic instruments must be used comprehensively in the experiment. They can be reasonably laid out according to the signal flow direction and based on the principles of simple connection, smooth adjustment, convenient observation and reading. The layout and connection between each instrument and the experimental device under test are as shown in the figure. As shown in 1.1. When wiring, please note that in order to prevent external interference, the common ground terminals of each instrument should be connected together, which is called common ground. The leads of the signal source and the AC millivoltmeter usually use shielded wires or special cables, the oscilloscope uses special cables, and the DC power supply uses ordinary wires.

Figure 1.1 Layout of commonly used electronic instruments in analog circuits

function signal generator

The function signal generator is mainly composed of a signal generation circuit, a signal amplification circuit and other parts. It can output three signal waveforms: sine wave, square wave and triangle wave. The output signal voltage amplitude can be adjusted by the output amplitude adjustment knob, and the output signal frequency can be adjusted by the frequency band selection and frequency adjustment knob. Its appearance is as follows:

Instructions for use:

Power switch: Pop the power switch button to the "off" position, connect the power cord, and press the power switch to turn on the power.

LED display window: This window indicates the frequency of the output signal. When the "external test" switch is pressed, the frequency of the external test signal is displayed. If the measurement range is exceeded, the overflow indicator light will light up.

Frequency adjustment knob: Adjust this knob to change the output signal frequency. Rotate it clockwise to increase the frequency. Rotate it counterclockwise to decrease the frequency. The fine-tuning knob can fine-tune the frequency.

Duty cycle adjustment: duty cycle switch, duty cycle adjustment knob, press the duty cycle switch in, the duty cycle indicator light will light up, and adjust the duty cycle knob to change the duty cycle of the waveform.

Waveform selection switch: Press a key corresponding to the waveform to select the desired waveform.

Attenuation switch: voltage output attenuation switch, the second gear switch combination is 20db, 40db, 60db.

Frequency range selection switch (and frequency meter gate switch): Press one of the keys according to the required frequency.

Counting and reset switch: press the count key, the LED display starts counting, press the reset key, the LED display is all 0

Counting/frequency port: counting and external measurement frequency input port.

External frequency measurement switch: Press this switch into the LED display window to display the frequency or count value of the external measurement signal.

Level adjustment: Press the level adjustment switch and the level indicator light will light up. At this time, adjust the level adjustment knob to change the DC bias level.

Amplitude adjustment knob: Adjust this knob clockwise to increase the voltage output amplitude. Adjust this knob counterclockwise to reduce the voltage output amplitude.

Voltage output port: Voltage output is output from this port.

TTL/CMOS output port: Output TTL/CMOS signal from this port.

Power output port: Power output is output from this port.

Frequency sweep: Press the frequency sweep switch, and the output signal of the voltage output port is a frequency sweep signal. Adjust the rate knob to change the frequency sweep rate. Changing the linear/logarithmic switch can produce linear frequency sweep and logarithmic frequency sweep.

Voltage output indication: 3-digit LED displays the output voltage value. When the output is connected to a 50Ω load, the reading should be ÷2.

DC regulated power supply

A DC regulated power supply can produce the required voltage or current value. The panel structure is as shown below:

Instructions for use:

Power switch: Press the switch to turn on the power.

ch1 port, ch2 port: can output adjustable voltage 0~30v, adjustable current 0~2a

ch3 port: can output fixed voltage 5v, fixed current 2a

Independent/combination switch: when the button is up, the two output voltages are used individually; when the button is pressed, the two output voltages are used in combination

Series/parallel switch: When the button is up, the two output voltages are connected in series; when the button is pressed, the two output voltages are connected in parallel

When the two outputs are used in combination, the main power supply of one channel can be adjusted and the slave channel can automatically track.

LED display: indicates the two output voltage and current values ​​respectively

Voltage adjustment knob: adjust voltage

Current adjustment knob: adjust the current

Oscilloscope

An oscilloscope is an electronic instrument used to observe various periodically changing voltage waveforms. It can be used to measure its amplitude, frequency, phase, etc. An oscilloscope mainly consists of oscilloscope tube, vertical amplifier, horizontal amplifier, sawtooth wave generator, attenuator and other parts. The yb43020b oscilloscope has a frequency band width of 0~20mhz; the vertical sensitivity is 2mv/div~10v/div. The scanning system adopts a full-band trigger automatic scanning circuit and has an alternate extended scanning function to achieve two-trace and four-trace display. (The overall panel is as shown below)

Instructions for use:

The operation part of the oscilloscope is shown in the figure below. The operation process is introduced below:

Power switch: Press this switch to turn on the power of the instrument and the indicator light will turn on.

Brightness: Adjust the brightness of the light trace. Rotate it clockwise to brighten the light trace.

Focus: Used to adjust the focus of the electron beam of the oscilloscope tube so that the displayed light spot becomes a thin and clear dot.

Light trace rotation: Adjust the light trace to be parallel to the horizontal line.

Probe calibration signal: This port outputs a square wave signal with an amplitude of 0.5v and a frequency of 1khz, which is used to calibrate the y-axis deflection coefficient and scanning time coefficient.

Coupling mode selection: Input coupling mode selection of vertical channels 1 and 2, ac: the DC component in the signal is isolated, used to observe the AC component of the signal; dc: the signal is directly coupled with the instrument channel, when the DC component of the signal needs to be observed Or this method should be used when the frequency of the signal being measured is low; grounding: the input terminal is in a grounded state, which is used to determine the location of the trace when the input terminal is at zero potential.

Channel 1 input socket ch1(x): dual-function port. In normal use, this port serves as the input port of vertical channel 1. When the instrument works in xy mode, this port serves as the horizontal axis signal input port.

Channel 2 input socket ch1(y): The input port of vertical channel 2, in xy mode, serves as the y-axis input port.

Sensitivity selection switch: Select the deflection coefficient of the vertical axis, which can be adjusted in 12 levels from 2mv/div to 10v/div. The appropriate level can be selected according to the voltage amplitude of the signal being measured.

Fine-tuning: Used to continuously adjust the deflection coefficient of the vertical axis. The adjustment range is ≥ 2.5 times. When the knob is turned counterclockwise enough, it is the calibration position. At this time, the signal can be read according to the position of the "volts/div" switch dial and the screen display amplitude. voltage value.

Vertical displacement: used to adjust the position of the light trace in the vertical direction.

Vertical mode: Select how the vertical system works.

ch1: Only the signal of ch1 channel is displayed.

ch2: Only the signal of ch2 channel is displayed.

Alternate: used to observe two signals at the same time. At this time, the two signals are displayed alternately. This method is suitable for use when the scanning rate is fast.

Intermittent: The two signals work intermittently, suitable for observing two signals at the same time when the scanning rate is slow.

Superposition: used to display the result of the addition of two signals. When the ch2 polarity switch is pressed in, the two signals are subtracted.

ch2 inversion: When this button is not pressed, the ch2 signal is displayed normally. When this button is pressed, the ch2 signal is inverted.

Horizontal displacement: used to adjust the position of the light trace in the horizontal direction.

Polarity: Used to select whether the measured signal triggers scanning on the rising edge or falling edge.

Level: used to adjust the measured signal to trigger scanning when it changes to a certain level.

Scan method: Select the method to generate the scan.

Automatic (auto): When there is no trigger signal input, the scanning trace is displayed on the screen. Once a trigger signal is input, the circuit automatically switches to the trigger scanning state. Adjusting the level can make the waveform stably displayed on the screen. This method is suitable for observation. Signals with frequencies above 50hz.

Normal: When there is no signal input, there is no light trace displayed on the screen. When there is signal input and the trigger level knob is in the appropriate position, the circuit is triggered to scan. When the frequency of the measured signal is lower than 50hz, this must be selected. Way.

Lock: After the instrument works in the locked state, the waveform can be displayed stably on the screen without adjusting the level.

Single: used to generate a single scan. After entering the single state, press the reset button and the circuit will work in single scan mode.