Lichuang EDA Simulation Classroom-Instrumentation

        In addition to using the built-in waveform diagram, EasyEDA also supports more commonly used simulation instruments. Currently, it supports: multimeter, oscilloscope, function generator, wattmeter and logic analyzer. Some better ones will be added in the future. We welcome your valuable comments on the model tools used. Below we will introduce the use of each instrument one by one.

1 multimeter

        A multimeter can be used to measure the voltage between two points during simulation, or it can also measure the current flowing through the circuit. Find the multimeter under the instrument category in the simulation base library and place it in the circuit. By default, the multimeter is a voltmeter type. It is connected in parallel to both ends of the device under test to obtain the voltage difference between the two points. If you want to measure current, select the multimeter, change the multimeter type to an ammeter in the multimeter settings on the right, and connect it in series to the circuit under test to get the current in the circuit.

        The test case is as follows, using a 10V DC voltage source and two 1K resistors in series. XMM1 multimeter is a voltmeter, connected in parallel on both sides of R1; XMM2 is an amperemeter, connected in series to the circuit to measure the current value of the current. According to the resistor voltage division, the voltage across R1 is half of the total voltage, which is 5V (R1=R2), and the current I=V1/(R1+R2)=5mA. The simulation results are consistent with the actual calculation.

2 function generator

        Function generator, an instrument used to generate common signal sources such as sine waves, triangle waves, and rectangular waves, can provide signal sources for circuits. Find the function generator under the instrument category in the simulation base library and place it in the circuit. Click to select the function generator on the drawing, select sine wave, triangle wave or rectangular wave as the input method in the property box on the right, set the frequency, duty cycle, amplitude, offset and rise/fall time generated by the instrument, set the column If it is grayed out, it means that this parameter does not need to be configured when outputting this waveform. For example, there is no need to configure the duty cycle and rise/fall time of a sine wave.

2.1 Parameter description         

(1) Frequency: The frequency of the function generator’s output waveform. The default unit is HZ. The size of the period can be calculated according to the formula T=1/f;                      

(2) Duty cycle: refers to the proportion of high-level duration to the cycle within a cycle;

(3) Amplitude: refers to the amplitude of the input waveform;

(4) Offset: that is, setting the size of the DC component in the signal, deviating from the zero point potential, and can set the positive and negative values;

(5) Rise/fall time: refers to the time required for the waveform to rise from the lowest point to the highest point and fall from the highest point to the lowest point. It can be set to a square wave or trapezoidal wave when configuring a rectangular wave.

2.2 Pin description

        The function generator has three wiring pins: +, COM, -

        COM ground terminal, 0V

        + Signal end, forward output, when connected to COM, the peak-to-peak value of the output signal is 2 times the set value

        - Signal end, reverse output, when connected to COM, the peak-to-peak value of the output signal is twice the set value

        If the +/- two pins are used as signal inputs, then the peak-to-peak value of the output signal is 4 times the set value.

        Taking sine wave output as an example, assuming that the signal output amplitude is 1V, when different bias voltages are set and connections are different, the output waveform voltage is as follows:

(1) + pin and COM pin as output

        When the bias voltage is -1V, the high level of the generated waveform is 0V and the low level is -2V;

        When the bias voltage is 0V, the high level of the generated waveform is 1V and the low level is -1V;

        When the bias voltage is 1V, the high level of the generated waveform is 2V and the low level is 0V;

(2)- pin with COM pin as output

        When the bias voltage is -1V, the reverse waveform generated has a high level of 0V and a low level of -2V;

        When the bias voltage is 0V, the reverse waveform generated has a high level of 1V and a low level of -1V;

        When the bias voltage is 1V, the reverse waveform generated has a high level of 2V and a low level of 0V;

(3) + pin and - pin as output

        When the bias voltage is -1V, the high level of the generated waveform is 0V and the low level is -4V;

        When the bias voltage is 0V, the high level of the generated waveform is 2V and the low level is -2V;

        When the bias voltage is 1V, the high level of the generated waveform is 4V and the low level is 0V;

2.3 Waveform selection

(1) A sine wave of 1KHz, amplitude 50mV, and amplitude 0 is configured as follows:

(2) 1KHz, 50% duty cycle, 50mV amplitude triangular wave configuration as follows:

(3) 1KHz, amplitude 50mV, rectangular wave with amplitude 50mV configured as follows:

3 oscilloscope

        Lichuang EDA supports a dual-channel oscilloscope for measuring the waveform changes of the measured signal in the circuit and the time relationship. After the simulation is run, the waveform change graphs of all test points will pop up. After clicking on the oscilloscope in the circuit, you can select "View Instrument" in the property box on the right to specifically view the waveform measured by the oscilloscope. By modifying the horizontal and vertical coordinate scales, the waveform display can be made more intuitive. Let’s take a look at the differences and usage of the two waveform display pages:

(1) All waveform display pages

        After the simulation is successful, the overall waveform display page will automatically pop up. Since the initial waveform will be relatively dense, you can use the left mouse button to select part of the waveform to enlarge it. The abscissa of the coordinate system represents time, the ordinate on the left represents voltage value, and the ordinate on the right represents current value. View the simulation results through the waveform names at the top corresponding to various waveform diagrams of different colors. When the mouse is clicked on the waveform chart, the abscissa time value and the ordinate voltage/current value of the clicked position will be automatically displayed, which is very clear and intuitive.

        On the right side of the corresponding menu bar, you can also customize waveform configurations, display in columns, and modify the background and color of arbitrary waveforms; it also supports direct export of CSV files and copying the image or saving the image locally.

(2) Oscilloscope waveform display page

        Click on the oscilloscope in the circuit and select "View Instruments" on the right to enter the oscilloscope waveform page, as shown below. When you first enter, if the waveform display in the picture is not intuitive enough and the waveform changes cannot be clearly seen, you can make the waveform display clearer by modifying the following time base scale and the amplitude scale of the two channels. The time base scale is used to modify the time represented by each grid on the X-axis; the scales on the A and B channels are used to modify the amplitude represented by a grid on the Y-axis. Both channels also support setting the Y-axis displacement, that is, The channel's waveform moves vertically up or down.

4 wattmeter

        Wattmeter is an instrument used to measure the power of AC and DC circuits. The wattmeter has two sets of test interfaces. The left one is the voltage input terminal, which is used in parallel with the circuit under test; the right one is the current input terminal, which is used in series with the current. The display panel screen displays the measured average power value, and the Power Factor screen below displays the measured power factor, with a value between 0 and 1.

5 logic analyzer

        Lichuang EDA provides a streamlined logic analyzer with 10 external signal inputs. Click on the logic analyzer and make settings on the right, mainly the settings of the threshold voltage and system clock frequency. When the external signal is higher than the threshold voltage, it is displayed as high level, and when it is lower than the threshold voltage, it is displayed as low level. After simulation, click on the meter and select View Meter in the property bar on the right to view the logic level signal.

        For actual instrument operation, please view the video series of Easy EDA Simulation Classroom. Learning how to use instruments can effectively help us quickly locate errors in the circuit. After learning how to use instruments, we next learn how to use voltage sources.

Video explanation link: https://www.bilibili.com/video/BV1Q44y1e7f3