How to use the digital oscilloscope
1 Fluorescent screen
The fluorescent screen is the display part of the oscilloscope. The horizontal and vertical directions of the screen each have a number of scale lines, indicating the relationship between the voltage and time of the signal waveform. According to the measured signal on the screen occupied by the number of frames multiplied by the appropriate constant of proportionality (V / DIV, TIME / DIV) can be derived from the voltage and time values.
2 oscillator and power supply system
(1) Power (Power) - oscilloscope main power switch. When this switch is pressed, the power indicator lights up, indicating that the power supply is on.
(2) Glow (Intensity) - Rotate this knob to change the brightness of the light spot and scanning line. Observation of low-frequency signals can be smaller, high-frequency signals, larger. Generally should not be too bright to protect the fluorescent screen.
(3) Focus (Focus) - Focus knob to adjust the size of the electron beam cross-section, the scanning line will be focused into the clearest state.
(4) Scale brightness (Illuminance) - This knob adjusts the brightness of the illumination behind the fluorescent screen. Normal indoor light, lighting darker good. In the environment of low indoor light, the lighting can be adjusted appropriately.
3 Vertical deflection factor and horizontal deflection factor
(1) Vertical deflection factor selection (VOLTS / DIV) and fine-tuning
Under the action of the unit input signal, the distance that the light point is deflected on the screen is called the offset sensitivity, and this definition applies to both the X-axis and the Y-axis. The reciprocal of the sensitivity is called the deflection factor. Vertical sensitivity is measured in cm/V, cm/mV or DIV/mV, DIV/V, and vertical deflection factor is measured in V/cm, mV/cm or V/DIV, mV/DIV.
Each channel in a trace oscilloscope has a vertical deflection factor selector band switch. There is often a small knob on each band switch that fine tunes the vertical deflection factor for each step. Turn this knob fully clockwise to the "calibration" position, where the vertical deflection factor value is the same as that indicated by the band switch. Turning this knob counterclockwise will fine-tune the vertical deflection factor. It should be noted that the fine adjustment of the vertical deflection factor may cause inconsistency with the value indicated by the band switch. Many oscilloscopes have a vertical expansion function, when the fine adjustment knob is pulled out, the vertical sensitivity is enlarged by several times (the deflection factor is reduced by several times).
(2) Time base selection (TIME/DIV) and fine tuning
Time base selection and fine tuning are used in a similar way to vertical deflection factor selection and fine tuning. The time base selection is also realised by a band switch, which divides the time base into a number of steps in the manner of 1, 2 and 5. The indication value of the band switch represents the time value for the point of light to move one frame in the horizontal direction. For example, in the 1μS/DIV mode, the point of light moving one frame on the screen represents a time value of 1μS.
The "Trim" knob is used for time base calibration and trimming. When the knob is turned clockwise to the calibration position, the time base value displayed on the screen is the same as the nominal value indicated by the band switch. Turning the knob counterclockwise, the time base is fine-tuned. 10MHz, 1MHz, 500kHz, 100kHz clock signals are available on the TDS lab bench, generated by the quartz crystal oscillator and frequency divider, with a high degree of accuracy, which can be used to calibrate the time base of the oscilloscope. The oscilloscope's standard signal source, CAL, is specifically designed for calibrating the oscilloscope's time base and vertical deflection factor. The Position knob on the front panel of the oscilloscope adjusts the position of the signal waveform on the phosphor screen.
4 Input Channel and Input Coupling Selection
(1) Input Channel Selection - There are at least three ways to select input channels: channel 1 (CH1), channel 2 (CH2), and dual channel (DUAL).
(1) CH1: Channel 1 is displayed separately;
(2) CH2: Channel 2 is displayed separately;
(3) ALT: two channels are displayed alternately;
(4) CHOP: two-channel intermittent display, used for dual-trace display when the scanning speed is slow;
(5) ADD: signal superposition of two channels. Maintenance to choose channel 1 or channel 2 is more.
(2) Input coupling mode Input coupling mode - AC (AC), ground (GND), DC (DC).
5 trigger
(1) Trigger source (Source) selection - to make the screen display a stable waveform, it is necessary to measure the signal itself or with the measured signal has a certain time relationship between the trigger signal added to the trigger circuit. Trigger source selection to determine the trigger signal from where to supply. Usually there are three trigger sources: internal trigger (INT), power trigger (LINE), external trigger EXT).
(2) Trigger coupling (Coupling) mode selection - the trigger signal to the trigger circuit has a variety of coupling methods, the purpose is to trigger the signal is stable and reliable. Here are a few commonly used: AC coupling, also known as capacitive coupling, DC coupling (DC) does not isolate the DC component of the trigger signal.
(3) Trigger level (Level) and trigger polarity (Slope) - Trigger level adjustment, also known as synchronous adjustment, which makes the scanning and the measured signal synchronisation. Level adjustment knob to adjust the trigger level of the trigger signal. Once the trigger signal exceeds the trigger level set by the knob, the scan is triggered. Turning the knob clockwise increases the trigger level; turning it anti-clockwise decreases the trigger level.
