Ten Daily Electronic Common Sense-Section 39

What does the clock divider register control?

Controls the CLKOUT frequency output to the microcontroller, it can disable the CLKOUT pin. In addition, it controls the dedicated receive interrupt pulse on TX1, receives comparator bypass, and the selection of BasieCAN mode and PeliCAN mode.

How to choose the right inductor？

• The main characteristic parameters of the inductor:
  1. Inductance L The inductance L represents the inherent characteristics of the coil itself and has nothing to do with the size of the current. Except for the special inductance coil (color-coded inductance), the inductance is generally not specifically marked on the coil, but marked with a specific name.
  2. Dimensions The dimensions of products produced by different manufacturers may have errors, including raw material errors, process errors, etc.
  3. Inductive Reactance XL The magnitude of the inductive coil’s resistance to alternating current is called inductive reactance XL, and the unit is ohms. Its relationship with inductance L and AC frequency f is XL=2πfL.
  4. Quality factor Q The quality factor Q is a physical quantity that represents the quality of the coil, and Q is the ratio of the inductive reactance XL to its equivalent resistance, namely: Q=XL/R. The higher the Q value of the coil, the smaller the loop loss. The Q value of the coil is related to the DC resistance of the wire, the dielectric loss of the skeleton, the loss caused by the shield or the iron core, and the influence of the high-frequency skin effect. The Q value of the coil is usually tens to hundreds. The use of magnetic core coils and multi-strand thick coils can improve the Q value of the coils.
  5. Distributed capacitance The capacitance that exists between turns and turns of the coil, between the coil and the shield, and between the coil and the plate is called distributed capacitance. The existence of distributed capacitance reduces the Q value of the coil and deteriorates the stability, so the smaller the distributed capacitance of the coil, the better. The distributed capacitance can be reduced by using the segmented winding method.
  6. Allowable error: the percentage obtained by dividing the difference between the actual value of the inductance and the nominal value by the nominal value.
  7. Nominal current: refers to the current that the coil allows to pass, usually represented by the letters A, B, C, D, and E, respectively. The nominal current values ​​are 50mA, 150mA, 300mA, 700mA, and 1600mA.

What is the internal standard method? How to choose the internal standard?

Internal standard method is an indirect or relative calibration method. When analyzing the content of a certain component in the sample, an internal standard substance is added to calibrate and eliminate the influence of the fluctuation of operating conditions on the analysis results, so as to improve the accuracy of the analysis results. 
Internal standard method is an important technique in the quantitative analysis of gas chromatography. When using the internal standard method, a certain amount of standard substance is added to the sample, which can be separated by the chromatograph without interference from the peaks of other components in the sample, as long as the peak areas of the internal standard substance and the component to be measured are determined. With the relative response value, the percentage content of the component to be tested in the sample can be obtained.
When using the internal standard method for quantification, the selection of the internal standard is a very important task. Ideally, the internal standard should be a known compound that is available in pure form so that it can be added to the sample in an accurate, known amount, and it should have substantially the same or as close to the composition as the sample being analyzed. Consistent physicochemical properties (such as chemical structure, polarity, volatility and solubility in solvents, etc.), chromatographic behavior and response characteristics, preferably a homologue of the analyte.
Of course, under chromatographic analysis, the internal standard must be sufficiently separated from the components in the sample. It should be pointed out that in rare cases, the analyst may be concerned about the recovery of a chemical in a complex process, in which case he can use a chemical that is easily fully recovered in the process It is not necessary to follow the selection principle mentioned above to determine the percent recovery of the compound of interest. 
When using the internal standard method for quantification, what factors will affect the ratio of the peak height or peak area of ​​the internal standard to the measured component?
The factors affecting the peak height or peak area ratio between the internal standard and the measured component mainly include three categories: chemical, chromatographic and instrumental. Variations in area ratios for chemical reasons often occur when analyzing replicate samples. 
Chemical factors include: 1. Poor mixing of the internal standard in the sample; 2. Reaction between the internal standard and sample components; 3. Variable purity of the internal standard, etc.
For a more mature method, chromatographic problems are more likely to occur, and some common chromatographic problems (such as leakage) have a greater impact on the absolute area and less impact on the area ratio. But if the change in absolute area is large enough to cause a significant change in area ratio, then there must be some significant chromatographic problem. For example, the injection volume changes too much, there is a big difference between the sample component concentration and the internal standard concentration, and the detector is nonlinear. The injection volume should be small and constant so as not to saturate the detector and integrator. If the method is considered to be reliable and the chromatographic solids appear to be normal, it is important to check the integration device and settings, slope and peak width positioning.
The strongest evidence for the suspicion of the integrating device is: the area ratio is variable, but the peak height ratio remains relatively constant. What should be paid attention to when making the internal standard standard curve? When using the internal standard method for quantitative analysis of color words, first prepare a certain amount of Perform chromatographic analysis on the mixture of the measured component and the internal standard sample in the weight ratio, measure the peak area, and make the relationship curve between the weight ratio and the area ratio, and this curve is the standard curve.
The chromatographic conditions used in the actual sample analysis should be as consistent as possible with those used in the preparation of the standard curve. Therefore, when making the standard curve, not only the chromatographic conditions (such as stationary phase, column temperature, carrier gas flow rate, etc.), but also the injection volume and the concentration of the internal standard should be indicated. When making the internal standard standard curve, each point does not completely fall on the straight line. At this time, the standard deviation of the ratio of the area ratio to the weight ratio and its average position should be obtained. In the process of use, single-point calibration should be carried out regularly. If the deviation between the obtained value and the average value is less than 2, the curve can still be used; if it is greater than 2, the curve should be redone. If the curve changes within a short period of time, the internal standard method should not be used for quantification.

What are the external pin functions of the NCP4303?

1. VCC (1PIN): IC power supply terminal, up to 30V voltage.
2. Min. Toff(2PIN): Use an external resistor to GND to adjust the minimum off time.
3. Min-Ton (3PIN): use an external resistor to GND to adjust the minimum on-time.
4. TRIG/DISABLE(4PIN): In CCM application, the fast input turns off the SR MOSFET.
5. CS(5PIN): The current detection terminal of the SR MOSFET, a resistor can be connected in series to adjust the turn-off threshold.
6. COMP(6PIN): Compensation inductance connection terminal, if not used, it can be connected to GND.
7. GND(7PIN): Common terminal of IC. Decoupling capacitor, the source of the SR MOSFET should be closely connected to this terminal.
8. DRV(8PIN): Gate drive terminal of SR MOSFET.

What is the main role of the C28X C code?

Declare all variables shared by C28X and CLA; assign variables to the linker by using CODE_SECTION#, which ensures that the file in the linker correctly places variables in memory blocks or information RAM; turns on the CLA clock; initializes the CLA data and program memory.

What is an integrated smart sensor?

This kind of intelligent sensor system adopts micromachining technology and large-scale integrated circuit technology, uses silicon as the basic material to make sensitive elements, signal conditioning circuits, microprocessor units, and integrates them on a chip, so it can be It is called integrated smart sensor/intelligent sensor.

What is the output function of the parity error signal?

If the U2ERE bit of the U2C1 register is set to “1”, the parity error signal can be used. If a parity error is detected during reception, a parity error signal is output, and the TXD2 output becomes “L” level. However, if the U2RB register is read in the output parity error signal, the PER bit becomes “0” (no parity error), and the TXD2 output also returns to the “H” level.

What is the electrochemical cell?

Electrochemical cells are devices that convert chemical energy into electrical energy through spontaneous redox reactions on electrodes.

What is the difficulty of the drive cable method?

The difficulty of the drive cable method is that the drive amplifier is required to strictly realize the amplification factor equal to 1 in a very wide frequency band, and the phase shift between the output and the input is zero.

What is the hardware system of the microcontroller?

As an entity, the hardware system provides the basis and conditions for the computer to work, but in order to make the computer work effectively, it must also have the cooperation of software. Generally speaking, the software system of the computer includes system software and application software and two parts. However, due to the limitation of hardware support and needs, the software system of single-chip microcomputer is relatively simple.