introduction
Mercury sphygmomanometers have some inherent shortcomings: First, the speed of deflation has a direct impact on the reading, the international standard deflation rate is 3 ~ 5mmHg per second, and the speed of deflation by different doctors will affect the measurement accuracy The second is that this method is based on human vision, hearing and coordination, which is difficult to standardize. To this end, this design starts with the blood pressure detection method, using the high-speed, low-power MN101EF32D single-chip microcomputer of Panasonic Corporation of Japan as the core of blood pressure measurement, control, data reading and writing, data display, and can accurately adopt the oscillometric method (oscillation Method) Measure blood pressure.
working principle
The oscillometric method (oscillation method) determines blood pressure based on the envelope of the amplitude change of the pressure oscillation wave of the cuff during decompression. The current consensus is that when the amplitude of the cuff pressure oscillation wave is at its maximum, the cuff pressure is the average arterial pressure. Arterial systolic pressure corresponds to the first inflection point of the amplitude envelope, and diastolic pressure corresponds to the second inflection point of the envelope.
hardware design
The basic working principle of the system is shown in Figure 1. The voltage signal output by the pressure sensor is first filtered by a low-pass filter, then the signal is converted into an input signal suitable for the single-chip microcomputer by the op amp circuit, and finally the analog sampling signal is converted into a digital quantity through the MN101EF32D single-chip microcomputer. The program performs digital filtering on the collected data and analyzes it to calculate the two key indicators of human blood pressure, "diastolic blood pressure" and "systolic blood pressure", and then the microcontroller immediately stores the data in external memory and displays these important data on the LCD .
Introduction of sensors and design of peripheral circuits
The sensor used by the sphygmomanometer is MPS-3100-006G piezoresistive pressure sensor, which is a Hui type bridge composed of four equivalent resistors. Its output voltage is proportional to the input pressure. Under ideal conditions, when the pressure is input, the resistance The value changes accordingly, but in fact the change of temperature will also affect the output value of its resistance. In addition, due to errors in crystal and circuit design and manufacturing, plus the impact of the packaging process, the zero offset is not zero. Therefore, individual components must be used to correct individual temperature compensation circuits. Its important indicators are as follows:
a. Sensor measuring range: 5.8 ~ 15 PSIG
b. Operating temperature range:? 40 ~ 85 ℃
c. Drive current: 1.5 ~ 3mA
d. Drive voltage: 5 ~ 15V
e. Zero drift:? 25 ~ 25mV
f. The temperature coefficient of resistance is: 0.2% / ℃
Because the blood pressure signal is taken from the arm, the measured signal is easily interfered by the position of the cuff and the movement of the arm. According to these professional characteristics, the system is required to have high input impedance, high gain, high common mode rejection ratio, low noise and low drift. As shown in Figure 2, T1 in the figure is the MPS-3100-006G piezoresistive pressure sensor. The entire circuit first converts the pressure signal into a voltage signal, and then performs amplification and filtering. U1, U2 in the picture are active op amp LM324, its input impedance is very high. After the signal of the pressure sensor is amplified, the closed-loop gain of the op amp is changed by adjusting the size of VR1 to adjust to the voltage input range suitable for A / D. The U1 op amp circuit is used to measure the pressure in the cuff. The measured data is used by the MCU to analyze and control the speed of inflation and deflation of the cuff. In addition, the U2 op amp circuit amplifies the AC signal separated by the C11 capacitor. This circuit measures the pulse wave of the human body. The collected data of the two circuits constitute the important calculation parameters of each index of the sphygmomanometer.
What is Battery Contact?
A battery contact is what connects the battery itself to an electrical circuit.
Battery contacts vary in shapes and sizes, depending on what type of battery. A typical battery has two connections: the positive and the negative.
Moreover, it is only proper that a battery contact has two terminals. Battery contacts have developed to be one of the most electrical components.
Battery contacts vary in shapes and sizes, depending on what type of battery. A typical battery has two contacts: the positive and the negative.
The circuit or load wouldn`t work with the battery without a battery contact.
Think about how a bridge connects two areas. The battery contact serves as a bridge here. It links the battery with the circuit (or whatever the battery sends power).
Remember, a battery has both positive (+ve) and negative (-ve) terminals. These terminals must create a firm contact with the circuit or load.
In constructing a battery contact, we`ll take into consideration the following factors;
The size of the battery: Remote batteries are smaller. It makes the difference from batteries for computers. Thus, a bigger battery will need a more considerable battery contact. If a least tiny battery contact was of use, there is bound to be a loose contact.
The type of load the battery would supply power: For example, the remote-control battery`s shape is small. It is because the remote only needs a small amount of energy. Load that requires larger batteries uses more oversized battery contacts. Also, the battery contacts would need better connectivity.
The position of the battery: Batteries can either be surface mounted or in-built. It`ll affect the method of construction of the battery contacts. Battery contacts are not interchangeable. Here`s why the mounting position is an integral part of design planning.
Note the positive (+ve) and negative (-ve) sides of the battery: Damage to the load is non-negotiable when both terminals are not placed well,
You can then proceed to choose the right shape and size of battery contact.
Then select a suitable material of your choice. The type of material chosen would help you predict durability. It will also help you expect if you would deal with corrosion in the future.
Depending on the type of material you chose, you`d then make metal stampings.
At this point., take care to make sure you`ve concluded on your design pattern. The stamping process is irreversible. The process involves cutting the metals to the desired shapes and sizes. Thus, you would not want to waste resources in case of a failed design pattern.
After stamping, then you can plate the materials. Plating involves the process of adding other metals for the desired performance.
Battery contact can be made of which metals?
Generally, materials used in making battery contact have different properties. The components are nickel-plated, copper alloys, and carbon steel. Depending on the type of contact used, battery contacts use various materials. These materials include:
Nickel-plated
This material is for battery contacts to prevent corrosion of the connections.
Steels
This material, when mixed with chromium and nickel, gives a strong resistance. The idea of this mixture is to achieve two things. The anti-corrosion quality of nickel and the strength of the steel is. It makes it one of the most expensive battery contacts.
Gold plate
Gold plate is better for environmental ruggedness. It can withstand almost all environmental conditions.
Beryllium copper
This is one of the best properties for making battery contacts. Beryllium Copper contains 2% of Beryllium that provides its strength. It also includes 98% of Copper for its electrical conductivity. This material, when heated, becomes very tough. It makes it withstand high stress. Beryllium Copper is for harsh conditions. It is also non-magnetic, which makes it suitable for wide use.
Phosphor bronze
Phosphor Bronze functions where strength matters for battery contacts. It also withstands corrosion and possible future wear. It also possesses one of the best conductivity levels. The material is by far one of the best when reliability is essential.
Brass
You can mix brass with a host of other materials. Depending on the fabric it is mix with, it may appear so tough. The materials include; phosphorus, nickel, tin, chromium, aluminum, lead, etc.
Gold
This is one of the best metal conductors. Gold works well for battery contacts due to its high metallic conductivity.
Silver Plating
This metal has high electrical conductivity and conducts heat better. Although the surface gets rough with ease, it is easier to maintain. Silver is also easier to solder compared to other metals used in plating. It is also an excellent anti-rust material for battery contacts.
Tin Plating
This material offers ease of stamping as it is soft and can get cracked with ease. Moreover, it is non-toxic and an excellent electrical conductor. Tin serves as a good anti-corrosion for producing battery contacts.
Copper Plating
Copper plating offers a wide variety of applications. They are to coat other metals like aluminum and Beryllium. They are soft, malleable, and easy to solder too.
Zinc Plating
If corrosion is a significant problem, then you need zinc in your production. Zinc has a record of dealing very with corrosion.
Different battery contact types
Surface Mounted Battery Contacts
This type consumes less space. They are on the exterior part of the gadget. It as well gives room for ease of installation in case of maintenance.
Cylindrical and Spring Battery Contacts
This type of battery contact is in the gadget or equipment body. It offers a designated compartment for the batteries and saves space too. Television remotes and walkie-talkies are examples of this type of contact. These types of contracts allow tremendous versatility to consumers. They provide firmness for batteries.
PC battery contacts
As the name implies, these battery contacts are for PCs. The design varies from brand to brand. Although, they`ll keep their peculiar qualities. They also have dedicated battery compartments for them.
Enclosure battery contacts
This is an advancement of the spring battery contacts. This enclosure battery contact consumes less space. They are also easier to install. Due to their compact nature, they are being used for remote hand controls-their usage cuts across almost all walks of life. Examples are wristwatches, digital timers, car remote controls, etc.
How to use the battery contact?
The above outline has the types of battery contacts above. How to use battery contacts depends on what you want to achieve.
Cylindrical or spring battery contacts. These are best for a gadget that has designated battery space. It`s cheap and can adjust with the different lengths of batteries. This type offers low resistance on contact with the battery.
Surface Mounted battery contacts are best for gadgets with no designated battery casing. This type is essential to achieve high spring tension. Also, it has low connection resistance. I prefer this type whenever I design small circuits on printed circuit boards (PCBs). The surface-mounted battery contacts allow me to change my design when there is a need for it.
Coin Cell Enclosure gives you to be immersed in use even with smaller gadgets. This type is for lower power gadgets. The battery used is often smaller compared to Others.
PC Battery contacts, as the name implies, they are for PCs.
Can you provide customized battery contacts?
Yes, ATKCONN can offer customized battery contacts. It only depends on which type of contact and the material type. With a clear picture of the battery contacts, you can make a customized battery contact. The advantage of customized battery contact is that it provides better designs.
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