55results about How to "Judgment failure" patented technology

The invention discloses a full-function digital-analog hybrid intelligent broadcast system for trains. The full-function digital-analog hybrid intelligent broadcast system mainly comprises broadcast consoles, broadcast master controllers, broadcast passenger room controllers, a digital communication network, an analog communication network and various power amplifier devices. The digital communication network is an Ethernet, the analog communication network comprises a UIC (international union of railways) 568 bus, the Ethernet is connected into CPUs (central processing units) of the broadcast passenger room controllers via network modules, the UIC568 bus is connected onto the CPUs of the broadcast passenger room controllers by sampling A / D (analog / digital) modules, the CPUs of the broadcast passenger room controllers monitor working 'heartbeat' signals of other devise in the system, and whether the total system in a current working mode fails or not is judged on the basis of the 'heartbeat' signals. According to the technical scheme, the full-function digital-analog hybrid intelligent broadcast system for the trains has the advantages that the broadcast system can run in the digital communication network and the analog communication network in a full-function manner, priorities of the networks can be self-defined, failures of the networks can be judged, and the networks can be voluntarily switched over.

The invention discloses a thyristor rectifier bridge parallel operation full digital current homogenizing control device, which comprises a regulator, a rectifier cabinet controller, thyristor rectifier bridges and a detection component. The regulator is a master controller; the rectifier cabinet controller is a slave controller; a terminal signal processing module regulates terminal voltage and current signals of a generator, so that the terminal voltage and current signals are suitable to be output to an analog-to-digital conversion module of a regulator controller; and a synchronization signal processing module regulates the anode voltage of the rectifier cabinet thyristor rectifier bridges, so the anode voltage is suitable to be output to a pulse formation module of the regulator controller to serve as a synchronization signal of the anode voltage of the thyristor rectifier bridges. Due to the adoption of digital closed loop control, full digital intelligent current homogenization for a plurality of parallel operation thyristor rectifier bridges under full-motion environment is realized by real-time sampling and control.

The invention discloses a high-voltage circuit breaker fault diagnosis method based on multi-feature optimization fusion. The method comprises the steps of: acquiring multiple groups of initial soundsignals YS(t) and vibration signals YZ(t) emitted in the switching-on and switching-off process of a circuit breaker; denoising, weighting and fusing each group of initial sound signals YS(t) and vibration signals YZ(t) to obtain a group of sound signals YS''(t) and vibration signals YZ''(t); extracting a feature vector of the sound signal YS''(t) by adopting a K-S test method; extracting a feature vector of the vibration signal YZ''(t) by adopting an EMD empirical mode decomposition method; fusing the feature vector of the sound signal YS''(t) and the feature vector of the vibration signal YZ''(t) into a feature matrix sample; selecting sample feature matrixes under various operation conditions of normal and fault states from the feature matrix samples in proportion; and inputting the selected sample feature matrixes to obtain a fault diagnosis result based on an FWA optimized SVM fault diagnosis model. According to the invention, through the concept of multi-sensor data fusion, the noise is effectively eliminated through weighted fusion of the data, so that the data is closer to a real value, and the fault diagnosis effect is effectively improved.

Provided is a paper sheet storage device which has a stage that can be raised or lowered for stacking and accumulating paper sheets, a plurality of sensors which are arranged in one row along the direction of movement of the stage and which detect the stage, an encoder for detecting the displacement of the stage, and a control unit for assessing whether at least one of the sensors has failed when the occurrence of a logical incongruity has been sensed in detection of the stage on the basis of information related to the position of the stage as detected by the sensors. As a result, it is possible to easily assess the failure of a sensor for detecting the storage quantity of the paper sheets.

Disclosed is an overvoltage protection circuit. An output voltage analog signal which basically changes along with an output voltage synchronously is obtained, and meanwhile, whether the output voltage analog signal and a feedback voltage represent totally opposite information or not is judged. On the basis, whether overvoltage is caused by the fault of a potential-divider network of an external resistor can be judged accurately, so as to provide effective overvoltage protection. Meanwhile, the invention also discloses an integrated circuit and a switch converter applying the overvoltage protection circuit.

The invention discloses a fault detecting method for a rail pressure sensor in a common rail system. The method comprises the steps that in the starting process, the rail pressure is controlled by an electronic pressure limiting valve in an open loop mode and the situation that as the rail pressure sensor drifts, an engine can not be normally started is prevented; under the specific working station, sufficient fuel oil is provided, the target rail pressure is obtained in a table look-up mode, the control current of the electronic pressure limiting valve is set according to the target rail pressure, and the pressure value measured by the rail pressure sensor is read and stored in a corresponding internal storage; the specific working station means that oil spraying is forbidden, an accelerator is zero, and the preset time interval is met; during halt, oil does not enter, the actual rail pressure is controlled in a mode under the specific working station, and pressure data measured by the rail pressure sensor are stored; after all working station data are obtained completely, pressure features at different points are analyzed, and whether the rail pressure sensor breaks down or not is judged. Through the fault detecting method, the working state of the rail pressure sensor can be comprehensively evaluated, and therefore the fault of the rail pressure sensor can be judged out accurately and reliably.

The invention provides a lamp signal control system for a non-volatile memory express solid state disk. The lamp signal control system comprises a non-volatile memory express solid state disk, a slave processor and a controller. The non-volatile memory express solid state disk is provided with a control module for transmitting an operation signal and a solid state disk position signal. The slave processor is electrically connected with the control module and is used for receiving the operation signal and the solid state disk signal, driving an operation indication lamp to light according to the operation signal and driving a fault indication lamp to light when detecting the fault of the non-volatile memory express solid state disk. The controller is electrically connected with the slave processor and is used for allowing a user to control the controller to drive a solid state disk position indication lamp to light.

The invention relates to a pump controller, a PLC platform and a sea water desalting plant. The pump controller includes a start-stop control unit, a condition distinguishing unit, a fault judging unit, a monitoring unit and a device running time recording unit, wherein the start-stop control unit is used for achieving starting and stopping instruction blocking and setting the starting and stoping operations indicated by the starting and stoping instructions to be pulse instructions for automatic reset; the condition distinguishing unit is used for setting and distinguishing pump control operation conditions; the fault judging unit is used for judging whether a fault occurs during the start and stop processes; the monitoring unit is used for monitoring the pump operation state during the start and stop processes; the device running time recording unit is used for automatically recording the device running time and the last start and stop time. According to the invention, the maloperation problem caused by operation instruction blocking is completely solved, the operation conditions are distinguished and queried, faults are effectively judged, and the occurrence rate of maloperation is reduced; in addition, the pump running time and the last start and stop time are automatically recorded, and a basis is provided for the device management, repair and maintenance.

The invention discloses an emergency brake device for an automobile brake failure and a control method thereof. The emergency brake device for the automobile brake failure comprises an electronic control unit, a friction braking module, and an energy recovery braking module. Under the condition of the total automobile brake failure, the electronic control unit of the device can collect travel speed signals of the automobile, and the friction braking module can frictionally brake a driven shaft of a braking force input gear engaged with a driven gear of a final drive through a friction plate, thereby converting energy generated in the driving process of the automobile into thermal energy, and reducing the speed of the automobile; the energy recovery braking module takes use of the rotation of the driven shaft of the braking force input gear engaged with the driven gear of the final drive to recycle the energy, converts driving energy into electric energy, and reduces the driving speed. The emergency brake device for the automobile brake failure and the control method thereof is simple in structure, easy to mount, and reliable to operate; operation states can be automatically adjusted according to different driving speed, and the automobile can be guaranteed to apply the brake under the condition of the total brake failure, meanwhile, energy can be recycled till the automobile stops steadily.

The invention provides a cooling system diagnosis method based on a TMM. The cooling system diagnosis method comprises a thermal management module used for controlling a cooling system, a single coolant temperature sensor for monitoring the temperature of a coolant and a warm air heat exchanger for heat exchange. The cooling system diagnosis method is a more simplified and more accurate diagnosisscheme developed based on the China standard requirement and based on the cooling system of the thermal management module (TMM). Compared with a diagnosis scheme of the single coolant temperature sensor, by the adoption of the cooling system diagnosis method, the result is more accurate, and the specific reason for judging the fault of the cooling system can be accurately judged; and compared withthe diagnosis scheme of a double-coolant temperature sensor, the cooling system diagnosis scheme is more simplified, and a thermostat is not required to be monitored for the temperature difference ofthe double-coolant temperature sensor. In this way, the diagnostic scheme provides the more simplified accurate cooling system diagnostic scheme for an engine using the thermal management module.

The invention discloses a computer power failure detecting instrument. The computer power failure detecting instrument comprises a single-chip microcomputer module, a voice module, an auxiliary power supply and a voltage comparator, wherein the auxiliary power supply supplies power for the modules; the voltage comparator is connected onto the power interface of a computer; the voltage comparator compares the voltage of the main board power interface with the voltage input by the auxiliary power supply, and outputs corresponding high-low electrical level; the single-chip microcomputer module is connected between the voice module and the voltage comparator, identifies the high-low electrical level output by the voltage comparator, identifies the failure point, and transfers a control signal to the voice module; the voice module identifies the control signal output by the single-chip microcomputer module, and broadcasts a corresponding failure language. Through the manner, the computer power failure detecting instrument can diagnose a computer power failure point, and is more accurate and intuitive when compared with conventional diagnosis methods.

The invention discloses a converter circuit fault detection method, a readable storage medium and a converter. The method comprises the steps that: the step 1, a converter controller acquires a current direction variable A representing a converter output point, a current actual voltage state variable B representing the converter output point and a current semiconductor switch command C of a converter switching device; the step 2, one of the current direction variable A, the voltage state variable B and the switch command C is selected in the current direction as an object to be compared, the predicted value of the object to be compared is predicted through the other two; and the step 3, the converter controller compares the differences between the predicted value and the actual value of the object to be compared to determine the state of the converter, determines and outputs the fault of the converter when the differences are different, and determines that the converter is normal when the differences are the same. According to the method, only the variable representing the current direction and the variable representing the voltage state are required to be obtained, and the fault determination is performed by combining the switching state of the switching device, so that the calculated amount is less, the error is small, and the determination is rapid, simple and convenient.

The invention discloses a weatherproof constant pressure linear array sound device. The weather proof constant pressure linear array sound device adopts a fixed structure member and a series connection fastener which fix and connect a plurality of adjacent water tanks in series; numbers of waterproof sound box assemblies can be customized; the number of the waterproof boxes can be fast increased and reduced in order to applicable to various application scenes; the waterproof sound box assembly comprises waterproof cloth, a waterproof ring, a waterproof loudspeaker, a waterproof plug-in connection seat and a waterproof connection line and thus a professional waterproof capability is guaranteed; and, particularly, the plurality of waterproof sound boxes are in circuit connection through the waterproof plug-in connection seat and the waterproof connection wire. The weatherproof constant pressure linear array sound device cannot only work all day, but also can improve sound intensity of a sound post and sound directive; a passive sound intensity display assembly can emit visible light with different intensity and prompts the user about the current sound intensity of the sound post; when voltage exceeds a threshold, visible light in different color is displayed as an alarm; the passive sound intensity display assembly can quickly determine faults of a voltage drop transformer, the passive sound intensity display assembly and the waterproof sound box.

The invention discloses a fault-tolerant control method and system for the single-phase Hall faults of a brushless direct-current motor. The method comprises the following steps that: a plurality of pieces of switching quantity information of three Hall sensors in a preset time range are obtained, the plurality of pieces of switching quantity information are coded, so that a plurality of switchingquantity information codes are formed; the plurality of switching quantity information codes are converted into a switching state sorting table; the fault switching quantity information of the Hall sensors in the switching state sorting table is obtained by comparing information in the switching state sorting table with information in a correct six-step state sorting table; normal switching quantity information corresponding to the fault switching quantity information is constructed, and wrong switching quantity information in the switching state sorting table is replaced with the normal switching value information, so that a new switching state sorting table can be formed; and the brushless direct-current motor is controlled to operate according to the new switching state sorting table.With the method adopted, the single-phase Hall faults can be rapidly and simply analyzed, and fault-tolerant control can be effectively implemented.

The invention provides a portable multifunctional hydraulic oil testing and maintenance device, which comprises a power assembly A, a medium pollution status detection and medium cleaning assembly B,and a leakage detection assembly C. The power assembly A comprises a motor, a hydraulic pump, a check valve, a pressure visualization measuring device, a coupling, an oil suction filter, a hydraulic hose, and a hydraulic quick-change connector. The medium pollution status detection and medium cleaning assembly B comprises a flow control device, a pollution degree detection device, a hydraulic oilcleaning device, a hydraulic hose, and a hydraulic quick-change connector; the leakage detection assembly C comprises a flow measurement device, a pressure maintenance device, a hydraulic hose, and ahydraulic quick-change connector. The device combines the detection of hydraulic oil pollution degree, the detection of hydraulic oil leaks, and the cleaning of hydraulic oil to easily detect and maintain the hydraulic oil in one machine; at the same time, the device has a portable design and is small in size, thus it is convenient to move and able to move freely on open spaces, and even can be carried by maintenance personnel on business trips.

The invention discloses a battery replacing cabinet capable of recovering offline batteries, and relates to the field of battery replacing cabinets, the battery replacing cabinet comprises a battery replacing cabinet main body, the battery replacing cabinet comprises a main control board, a touch display screen and more than one battery compartment, and the touch display screen is connected with the main control board; the battery compartment is provided with a compartment control plate, a charging module, an electric control lock and a compartment door, and a battery module is separably connected in the battery compartment; the charging module and the electric control lock are electrically connected with the bin control plate, and the electric control lock is connected with the bin door in a matched mode to open or close the battery bin. According to the battery replacement cabinet, when the main control board cannot acquire the battery information of the battery compartment in a wired communication mode, the battery information of the battery module is acquired in a Bluetooth communication mode, and whether the battery module breaks down or is disconnected is judged; and if not, the warehouse control board corresponding to the offline battery module and the main control board are recovered to be in a wired communication mode for management and control without intervention of maintenance personnel.

The invention discloses a wirelessly-powered electric water heater and a power supply and control method of the wirelessly-powered electric water heater. The wirelessly-powered electric water heater comprises an energy emitting end, an energy receiving end, a heating pipe, a detector and a processor, wherein the energy emitting device is connected with an alternating-current power source and used for converting the alternating-current power source into a high-frequency alternating-current power source and converting the high-frequency alternating-current power source into a high-frequency electromagnetic field; the energy receiving end is used for generating electric energy by means of the high-frequency electromagnetic field; the heating pipe is used for heating water in an inner container of the wirelessly-powered electric water heater by means of the electric energy generated by the energy receiving end; the detector is used for detecting the current of the high-frequency alternating-current power source; and the processor is used for judging a circuit fault of the energy receiving end according to the current. According to the wirelessly-powered electric water heater, the electricity utilization safety of the electric water heater can be further improved.

The invention relates to the technical field of motor detection, in particular to a motor fault detection device which comprises a fault maintenance platform. A motor placing groove is formed in the middle of the top surface of the fault maintenance platform. Motor fixing plates are arranged on the left side and the right side of the motor placing groove. A vertical second electric push rod is arranged on the rear side of a fixing block. A horizontal rotating shaft is arranged at the top of the second electric push rod. A first bevel gear is fixed to the left side of the rotating shaft. A second bevel gear is meshed with the bottom of the first bevel gear. A rotating connecting rod is fixed to the bottom of the second bevel gear, and a rotating speed detection assembly is connected to thebottom end of the rotating connecting rod. The motor fixing plates and the motor placing groove are arranged, the motor placing groove can stably fix a flange piece at the bottom of a motor body, thefront side and the rear side of the motor body can be clamped through the motor fixing plates, fixing teeth on the motor fixing plates are embedded between fins on the motor body, and fixing is more stable.

An electric working machine comprises a motor, a switch, a drive device, a brake device, and a failure determiner. The switch is configured for operation by a user, has an on-state and an off-state. The drive device is configured to drive the motor in response to the switch being placed in the on-state. The brake device is configured to control deceleration of the motor to a stopped state in response to the switch being placed in the off-state. The failure determiner is configured to monitor deceleration of the motor during controlled deceleration and to determine whether the brake device has failed based on the monitored deceleration.

The invention discloses a method and a system for quickly detecting demagnetization of a permanent magnet synchronous motor of an electric automobile, which relate to the technical field of automobile detection and comprise a data acquisition step, an effective working condition determination step, a current change determination step, an efficiency determination step, a critical threshold determination step and a demagnetization aging judgment step. According to the method, the demagnetization aging degree of the motor is analyzed, the calculated amount is small, online real-time detection can be achieved, and the reliability is high.

An error variance detection method of CAN communication system according to an exemplary embodiment of the present invention may include storing an error information that corresponds to the communication error in a network management start message, if an communication error is occurred in the CAN communication system, by at least one of a plurality of slave ECU, transferring the network management start message to a master ECU, by at least one of a plurality of slave ECU, determining whether there is or is not the error information in response to the network management start message, by the master ECU, detecting the error information from the network management start message, if there is the error information, by the master ECU, and transmitting the error information detected by a demand of a diagnosis device to the diagnosis device, by the master ECU.

The method for diagnosing a cooling system based on a TMM module designed by the present invention includes a thermal management module for controlling the cooling system, a single coolant temperature sensor for monitoring the temperature of the coolant, and a warm air heat exchanger for heat exchange; the present invention It is a simplified and more accurate diagnosis scheme developed based on the requirements of the national standard and based on the cooling system using the TMM module (thermal management module). Compared with the diagnosis scheme of the single coolant temperature sensor, the results of the present invention are more accurate, and the specific cause of the cooling system failure can be judged more accurately; The temperature difference of the coolant temperature sensor is used to monitor the thermostat. From this point of view, this diagnostic scheme provides a more simplified and accurate cooling system diagnostic scheme for engines using thermal management modules.

The invention discloses a control system of a building talkback indoor device, which comprises a system bus interface, a power-switching circuit, a power supply circuit of the indoor device, a video input impedance matching circuit, a video output drive circuit, an audio duplex communication circuit, an audio power amplification circuit, two multi-way option switches, a data communication transceiver, a microprocessor, a interface status indicating lamp, a electric level state detection circuit and at least two indoor device interfaces; the power supply circuit of the indoor device provides the indoor device with the power supply with various voltages; the video input impedance matching circuit and the video output drive circuit provide the indoor device with the video signal access; the audio duplex communication circuit, the audio power amplification circuit and the multi-way option switches provide the indoor device with the two-way audio signal access; and the microprocessor is connected with the data communications transceiver and the electric level state detection circuit, thereby achieving the state detection and control of the indoor device. The control system is shared bya plurality of indoor devices, thereby reducing the cost of the device, and has functions of failure isolation and video transmission compensation.

The present invention relates to a terminal cover for a circuit breaker, which comprises a terminal cover body with an opening at the upper end and a push-pull upper cover covered on the upper end ofthe terminal cover body. The upper ends of the front and rear sides of the terminal cover body are provided with transverse clamping grooves; the left end of the terminal cover body is provided with aliftable fixed inserted rod; The lower parts of the front and rear ends of the push-pull upper cover are respectively provided with transverse clamping strips which are slidably engaged with the transverse clamping grooves; and the left bottom surface of the push-pull upper cover is provided with a limit slot which is convenient for upward insertion of the fixed inserted rod. The invention is simple and reasonable in structure and can be assembled and disassembled quickly; it is convenient to observe the wiring conditions of the terminals in the terminal cover; and then it can be quickly judged whether the circuit breaker terminal is faulty or not.

The invention provides a method for judging the optical catastrophe type of a semiconductor laser chip, which solves the problems of high judgment cost, long judgment time and low production efficiency of existing semiconductor laser chips COBD and COMD. The method includes: Step 1, setting the loading current; Step 2, loading the loading current on the semiconductor laser chip; Step 3, collecting the current-power curve and current-voltage curve of the semiconductor laser chip; Step 4, if the current-power curve If the current-voltage curve suddenly drops and the current-voltage curve suddenly rises, it is judged that the optical catastrophe of the chip is COMD; if the current-power curve suddenly drops and the current-voltage curve suddenly drops, it is judged that the optical catastrophe of the chip is COBD. The method of the present invention does not require professional equipment, and only needs to collect the current, power value and voltage value in the test process to judge COBD and COMD. The detection equipment is simple and the cost is low, and only ordinary technicians can realize the judgment of failure .

The invention discloses a lithium battery residual capacity and fault display system and method and an electric bicycle, and relates to the technical field of lithium batteries. The problem that the lithium battery residual capacity is not displayed accurately in the prior art is solved. The lithium battery residual capacity and fault display system comprises a power management chip, a control chip which is in communication connection with the power management chip, and a display instrument connected with the control chip. The power management chip is connected to all lithium batteries to be detected and is used for receiving the temperature and voltage signals of the lithium batteries. The control chip is used for judging whether the temperature and voltage signals transmitted by the power management chip are normal values or not, and transmitting the judgment result to the display instrument. The display instrument is used for displaying the battery residual capacity and battery faults. The lithium battery residual capacity and fault display system and method and the electric bicycle have the advantages that the lithium battery residual capacity or a fault is displayed in a percentage mode or displayed by the number of lit LED lamps through the display instrument, and therefore a user can acquire the information of the lithium battery residual capacity or the lithium battery fault more visually.

The invention discloses a weatherproof constant pressure linear array sound device. The weather proof constant pressure linear array sound device adopts a fixed structure member and a series connection fastener which fix and connect a plurality of adjacent water tanks in series; numbers of waterproof sound box assemblies can be customized; the number of the waterproof boxes can be fast increased and reduced in order to applicable to various application scenes; the waterproof sound box assembly comprises waterproof cloth, a waterproof ring, a waterproof loudspeaker, a waterproof plug-in connection seat and a waterproof connection line and thus a professional waterproof capability is guaranteed; and, particularly, the plurality of waterproof sound boxes are in circuit connection through the waterproof plug-in connection seat and the waterproof connection wire. The weatherproof constant pressure linear array sound device cannot only work all day, but also can improve sound intensity of a sound post and sound directive; a passive sound intensity display assembly can emit visible light with different intensity and prompts the user about the current sound intensity of the sound post; when voltage exceeds a threshold, visible light in different color is displayed as an alarm; the passive sound intensity display assembly can quickly determine faults of a voltage drop transformer, the passive sound intensity display assembly and the waterproof sound box.

The invention discloses a detection method for judging whether a nitrogen-oxygen sensor is invalid. The method comprises the following steps of: S1, opening the nitrogen-oxygen sensor, checking whether the line connection and the communication between the nitrogen-oxygen sensor and a control unit are normal; S2, preparing a large cube box and a small cube box, placing the nitrogen-oxygen sensor inthe small cube box, exposing the detection end of the sensor, and then placing the small cube box into the large cube box, and pumping the large cube box into a vacuum state; S3, judging the detection accuracy of oxygen; and S4, judging the detection accuracy of the nitrogen-containing gas. According to the detection method for judging whether the nitrogen-oxygen sensor is invalid, the accuracy of the detection result of the nitrogen-oxygen sensor and whether the accuracy meets the accuracy requirements of the detection can be accurately judged by inputting a certain amount of oxygen or nitrogen-containing gas into a vacuum box of known volume and comparing the detection result with the calculation result.

The invention discloses an easy-maintaining pipeline electric wire. The structure of the easy-maintaining pipeline electric wire includes a power supply plug, a horizontal pipeline wire, a power socket, a vertical pipeline wire, and a grid interface; the power supply plug is fixed outside the wall through cement; and the horizontal pipeline wire is electrically connected to the right side of the power supply plug. In the case of a sudden increase of the current in the circuit and a voltage change, the shape of a magnet absorbed belt can be changed to compress a corresponding needle-nosed belt,so that the needle-nosed belt causes a stimulating slide on a rolled sheet and makes the rolled sheet carry out an action effect of the corresponding circuit, so that people can accurately determinewhich wire is faulty after removing the wire; through the collision occurrence effect of collision particles in a rotating cone and the effect of color-changing of a certain color-changing belt, the fault of a certain line can be judged visually and acoustically; and the double judgment is more accurate; therefore, the waste of maintenance time caused by misjudgment is prevented.

The invention discloses a converter circuit fault detection method, a readable storage medium and a converter. The method comprises the steps that: the step 1, a converter controller acquires a current direction variable A representing a converter output point, a current actual voltage state variable B representing the converter output point and a current semiconductor switch command C of a converter switching device; the step 2, one of the current direction variable A, the voltage state variable B and the switch command C is selected in the current direction as an object to be compared, the predicted value of the object to be compared is predicted through the other two; and the step 3, the converter controller compares the differences between the predicted value and the actual value of the object to be compared to determine the state of the converter, determines and outputs the fault of the converter when the differences are different, and determines that the converter is normal when the differences are the same. According to the method, only the variable representing the current direction and the variable representing the voltage state are required to be obtained, and the fault determination is performed by combining the switching state of the switching device, so that the calculated amount is less, the error is small, and the determination is rapid, simple and convenient.