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This device is a metal oxide semiconductor. As temperature change, there is an exponential decline in resistance inside the thermistor. However, a narrow range is required, the output is often linearized by the device. They are very accurate with 0.1 − 0.2°C increments possible. They are advantageous in that thermistors can be made very small and are durable, unless subjected to severe changes in temperature.
Thermocouples are based on the fact that junctions of two different types of metals produce a small voltage or current change in response to temperature. This is commonly known as the Seebeck effect. The junctions in clinical temperature measurement are usually copper and constantan (copper with 40% nickel). This kind of combination will produce a voltage change of 40 mV per oC. These devices are very accurate and available in very small sizes.
Infrared tympanic thermometer
This is a device which measures radiant infrared, commonly from the ear drum, which is detected by a thermopile which is a collection of thermocouples. This signal is then converted within around 5 s into a temperature reading which is very accurate for core temperature. This kind of measurement also good for temperature measurement.
Pyrometer is an instrument or device for measuring temperature. Although the term pyrometer is generally considered to apply to instruments that measure high temperatures only, some pyrometers are designed to measure low temperatures. Two common types of pyrometers are the radiation pyrometer and optical pyrometer.
A heated object will gives off electromagnetic radiation. If the object is sufficiently hot or in very high temperature, it will give some physical changes such as off visible light, ranging from dull red to blue-white. Even if the object is not hot enough to glow, however, it gives off infrared radiation.
An optical pyrometer determines the temperature of a very hot object by the color of the visible light it gives off. The color of the light can be determined by comparing it with the color of an electrically heated metal wire. In one type of pyrometer, the temperature of the wire is varied by varying the strength of the current until the operator of the instrument determines that the color of the wire matches the color of the object. A dial, operated by the current that heats the wire, indicates the temperature.
A radiation pyrometer determines the temperature of an object from the radiation (infrared and, if present, visible light) given off by the object. The radiation is directed at a heat-sensitive element such as a thermocouple, a device that produces an electric current when part of it is heated. The hotter the object, the more current is generated by the thermocouple. The current operates a dial that indicates temperature.
An electrocardiograph (ECG) is a recording of the electrical activity on the body surface generated by the heart. ECG measurement information is collected by skin electrodes placed at designated locations on the body.
Figure below shows the Block diagram of electrocardiograph (ECG) which processing and heart condition monitoring system. There are some main parts that very important in this device
Sensor or electrode
To detect the heart beat, electrode is use by attached to the skin at specific part on human body. Electrodes are commonly made of silver or silver chloride components that are attached to the main unit of the machine
To perform any sort of analysis on a bioelectric signal, the signal needs to be amplified to a level which an analog to digital converter that can sample the data with a high resolution. The amplifier will convert electric signal from electrode and convert the information. As well, the amplifier circuitry needs to include level shifting circuitry such that the signal is positive and has a similar dynamic range as the Analog to Digital conversion.
ECG signal is usually corrupted with different types of noise. These are baseline wander introduced during data acquisition, power line interference and muscle noise or artifacts as discussed in the previous sections. Prior to applying different signal processing techniques for extraction different ECG features which are of clinical interests, data needs to be filtered in order to reduce noise and artifacts.
Detection of QRS complex is particularly most important in ECG signal processing. The information obtained from QRS detection, temporal information of each beat and QRS morphology information can be used for the improvement of performance.
Heart rate calculation
Heart rate is a vital sign to determine the patient's condition or well being. It can be easily computed from ECG. Heart rate can be computed using various methods, for example, over one minute time period simply by counting the number of heart beats would give us the heart rate in beats per minute. However, the heart rate monitoring tool should avoid such wrong results.
Complete circuit diagram of Electrocardiography (ECG)
Given 4-30mA is grounded via a standard 250ohm. And the Vout is 0-10V.
In the case that R1=R2, R3=R4
Equation 1 Vo=R3/R1(V2-V1)
For the ratio of input and output:
Then, subtitutude the ratio in the equation 1
From the subtitution, we know that Vin2=5V
Voltage to frequency
The voltage to frequency converter changes a DC input voltage into a string of pulse, whose repetition rate (frequency) is proportional to the magnitude of the input voltage. The pulses are counted for a fixed period of time, and the final count is proportional to the measured voltage
A voltage to frequency converter (VFC) is an oscillator .Its frequency is linearly proportional to the control voltage. It can consume very small amount of power and integrates noise. The voltage to frequency converter(VFC) is also very useful for telemetry applications, since the VFC, which is cheap ,small, and low-powered can be mounted on the experimental subject (patient, artillery shell, wild animal, communication etc.) and communicate with the counter by the telemetry link.
Voltage to frequency converters are sometimes needed in some instrumentation applications. In the present correspondence we shall discuss a new voltage-to-frequency converter which can obtain the excellent linearity between the input voltage and the frequency of oscillation. The linearity of this converter can be improved by adjusting the variable resistor connected to the op-Amp. There are two common VFC architectures: the current-steering multi vibrator VFC and the charge-balance VFC. The charge-balanced VFC may be made in synchronous (clocked) or asynchronous forms. There are many more VFO (variable frequency oscillator) architectures, including the 555 timer which is a unique functional building block, the key feature of VFCs is linearity, and a few VFOs are very linear.
Frequency to voltage
In this case, commonly the frequency to voltage converter performs the inverse operation of the voltage to frequency converter. Frequency to voltage converter produces an analog output voltage whose amplitude is a function of the frequency of the input signal. This type of circuit may respond to a sine wave, a square wave or a pulse train. An ideal frequency to voltage converter produces an analog signal linearly proportional to the frequency.
Purpose Differential Pressure Flow meters Work
Differential pressure flow meters are used Bernoulli's equation to measure flow of fluid in pipe. Differential pressure in flow meters introduces a repress in the pipe that establishes a pressure drop in the flow meter. The flows are increases, will created more pressure drop. Impulse piping route the downstream pressures and upstream and pressure of flow meter to transmit that use to measures the differential pressure and to define the fluid flow.
This device, the Bernoulli's equation stated that the pressure drop in the repress is proportional of the flow rate to the square. By using this relationship, 10% of full scale flows produce only 1% of full scale to differential pressure. At 10% of full scale flow, the differential pressure in flow meter accuracy or not is depend the transmitter being accurate over 100:1 range of the differential pressure.
Differential pressure transmitter accuracy is degraded at low differential pressures in the range; so that the flow meter accuracy can be similar degrade. Hence, this is non linear relationship can have turndown of differential pressure of flow meters and an unfavorable effect on the accuracy.
Different geometries are used for different measurements, including the orifice plate, low-loss flow tube, V-cone, flow nozzle, laminar flow element, Venturi tube, and segmental wedge.
Operation of differential pressure in flow meters
Differential pressure in flow meters inferentially to measure the vapor in pipes, flow of liquids and gases, for example water, industrial gases, chemicals, steam, cryogenic liquids and air. Have to be careful when using differential pressure flow meters to fluids with higher viscosity, such as some foods and hydrocarbons, because the accuracy can degrade when lower the Reynolds number.
This flow meter applies relatively to clean fluids. With correct attention to materials of the construction, the flow of the corrosive fluids, for example like found in the chemical industry, the flow can be easily be measured.
By purging impulse piping and inert fluid, the dirty fluids can measure. When using differential pressure flow meters in dirty services have to be careful because cause incorrect measurements and the dirt can plug the impulse piping. Diaphragm seals can be applied in these applications, yet one should always remember that diaphragm seals can be degrade the performance of differential pressure transmitter system, and therefore, degrade the performance of flow measurement system.
Differential pressure flow meters are familiarly applicable to a lot of flows in normal industries, such as chemical, mining, wastewater industries, pulp and paper, petroleum, petrochemical, water, and mineral processing. Other flow measurement technology may have better performance than differential pressure flow meter in a lot of applications. Yet the differential pressure flow meters are still to use spread due to long lasting user as familiarity with the technology.
An orifice plate is a cramped of consisting of a flat plate with a hole for the flow stream that is placed in the pipe between two flanges. A standard orifice plate that commonly used is simply a smooth disk with a round, sharp-edged inflow aperture and mounting rings.
A Venturi tube is a constriction consisting of a streamlined expansion and reduction of the piping containing an inlet section, throat, and outlet section.
A flow nozzle which consist the contoured plate to form the flow stream can be narrow placed this pipe between twp flanges.
Pitot tube in differential flow meter is a probe with an open tip (Pitot tube) is inserted into the flow field. The tip is the stationary (zero velocity) point of the flow. It is pressure, compared to the static pressure, is used to calculate the velocity flow. Pitot tubes can measure flow velocity at the point of measurement.