High precision and intelligent electronic multihead weigher

Author: Smartweigh–Multihead Weighter

1 Introduction With the rapid development of contemporary electronic information technology and electronic information technology, electronic multihead weighers have been widely used in various social and economic industries. The functions of formula and other functions are deeply favored by customers. The key of intelligent electronic multihead weigher is composed of two major system softwares.——The inspection and data processing system and the human-computer interaction technology page are composed of the inspection and data processing method system. The measured results are displayed under the control of everyone, such as information and copying. The article mainly introduces the inspection part of the system software in detail, including the automatic calibration of the power supply circuit of the sensor. Design scheme sensor calibration responsive and its dual cpu middle work. 2 System overall scheme design communication. The key to scientific research is the way to complete the system software intelligent system. The multihead weigher monitoring system is mainly composed of sensor operational amplifier, data acquisition (analog/digital conversion) power supply circuit, intermediate control components, feedback power supply circuit, external compensation and switching power supply application.

The function of the power supply circuit is to replace the net weight value number with the slightly variable working voltage number according to the resistance strain gauge transmission flap, and enlarge it to the working voltage data accepted by the appropriate analog/digital conversion processing chip. Signal and carry out A/D conversion, the system error of the instrument panel is mainly caused by this part, so the design scheme of this part is related to the precision of the whole system software. The central processing unit is not responsible for the operation and operation of the whole system software, and carries out data processing Method, automatic calibration, automatic transformation of It process, responsive building transmission device replacement The power supply circuit that carries out instruction and data transmission in the middle of the CPU of the page system software. The switching power supply system software provides an excellent power supply and distribution system for the smooth operation of the system software, and provides a high degree of power supply bridge switching power supply. 3 Hardware development The key to the hardware development of the electronic scale monitoring system includes 3 parts: operational amplifier, analog/digital conversion power supply circuit, CNC machine tool resistor The integrated operational amplifier processing chip AD525C used is shown in Figure 2. The output temperature drift working voltage should be lower than 25. The temperature drift working voltage should be lower than the common rejection ratio CMR, which is about 90dB when the general gain is greater than that of the large discrete system. 0.003^ (when G=l). As a sound amplifier, AD524 contains high-precision resistors for tt1WG=l, 10, 100 and 1000 pin-type SI process: make the JWRG2 end of the tube larger and relative After the multiplier selection pin is connected in advance (at this time, the RG1 is not connected to the nose), the amplification function of the relative magnification can be completed. Except for this kind of internal matching method, when the specified gain value is from 1 to 100.

When the transition is continued, AD524 also has another way to control the gain value. A sliding rheostat RG is used to connect the tube 3 (RG2) of the AD524 processing chip to pin 16 (RGD), and the resistance value corresponding to G RG is RG-40K/(G-l)3.2 digital conversion power supply circuit. In this design scheme, the 14-bit multiple S! analog/digital converter MAX194 produced by MAXIM is selected. The processing chip has capacitor-type DACSPWM, Sampling mouthpiece holder, 10 calibration DACs, serial communication and control not only have the characteristics of high-speed operation, high precision, power consumption, etc., but also its internal calibration power supply circuit calibrates the linearity and offset difference, which can be adjusted without external adjustment. Maintain all 18 fixed performances within the allowable temperature range. The characteristics of serial communication make the IB connect to most of the emblem control boards immediately, which greatly simplifies the system software circuit principle. In addition, it simulates analog switching power supply and data switching. The structure of the power supply separation also greatly reduces the harm of data-noise coupling. Its key characteristics are: the screen resolution is 14 bits: the reason for the deviation of the integral discrete system is 0.33%, and the ratio of data signal to noise plus and lost frames is 82dB; 9. When the reference working voltage is +9V, when the input working voltage changes from 0 to 9V or a 5 to +9V, the output data volume changes from OOOOH to 3FFFH. The preprogrammed flow is used to manipulate the change of its resistance value. This design scheme selects the non-volatile CNC machine tool resistor X9241 manufactured by Xicor Corporation, including 4 resistor arrays, each array including 63 resistor modules, In the middle of each module and 2 nodes, there are tap points that can be browsed by the dragging module. The position of the dragging module in the array is controlled by the customer according to the two-wire serial bus socket, and the detailed address of the physical component is A0 -A3 key in the end case to define——X9241 compares the data flow analysis of serial communication with the situation of the detailed address input terminal. When all 4 detailed address bits are relatively successful, the party will respond with a reply to indicate that it is selected. And each X9241 has 4 resistor arrays, so the two I/O lines of the CPU can operate up to 64 resistor arrays in total, and each resistor array is associated with a drag terminal register ( WCR) and four 8-bit register addresses, all of which can be loaded or read by the customer.

The content of the drag terminal count memory (WCR) manipulates the bit JL of the drag terminal in the resistor array. In the command structure of X9241, in addition to the read-write capability memory and the command to transfer data between each memory, there is also a command that will Let the drag terminal (WCR) iS/minus a minimum unit command INC-WIPER, each time an INC-WIPER is executed, that is, the drag terminal will move one in 63 resistor modules, which shows the design scheme of the zero adjustment program flow A huge convenience, 4 system principles 1) Reset“After the system software is powered on, the reset solution is first performed. If there is no system command from the control panel-human-computer interaction technology page, the system software will first load the status word in the EEPROM every time the calibration is started, and carry out identification. Automatically activate the main parameters such as the original preset or the safe channel method, base value, and gain set before the previous standby. Then the CPU gives the command to convert the multi-channel analog switch AD7502 to the fourth safe channel, and the input terminal ① and ② of the instrument and equipment amplifier AD524 are short-circuited, and the CPU controls the resistance of the CNC machine tool according to the pre-programmed system. The resistance value of the 10K resistor in the device X9241 is changed, and the automatic zero adjustment of the programmable controller gain value instrument equipment amplifier is performed. 2) Sensor adjustment” When the operator determines that the electronic multihead weigher has no load, the sensor zero adjustment command is obtained according to the human-computer interaction technology page, and the CPU accepts the information transmitted by the CPU of the human-computer interaction technology page according to serial communication. content, distinguish the group number of the sensor that must be adjusted, adjust the corresponding CNC machine tool resistor X9241, carry out initial adjustment and fine adjustment respectively, and the power circuit performs the daily task of automatic zero adjustment of the sensor. 3) System software zero adjustment , After the CPU adjusts the gain value amplifier and the sensor (as necessary) of the programmable controller, the CPU collects the remaining working voltage residual value of the zero point according to the A/D converter MAX194 and stores it in the EEPROM * wait until everything is normal When weighing the child, subtract this value again. "If the natural environment changes greatly and the CPU does not receive the zero adjustment command, the customer can issue the zero adjustment command anytime and anywhere according to the interactive page of the machine, so that the electronic multihead weigher will be calibrated again. In addition, for the zero point data error generated by the A/D, MAX194 will automatically correct the stupid point of the A/D within the original 50ms of each power on. The CPU can also use the A/D converter MAX194 to carry out the actual operation of the adjustment. "Generally speaking, this electronic multihead weigher has the function of automatic and real-time zero adjustment of excellent system software" to ensure its high-precision weighing work.#4 ) Sensor responsive function. This system software has a unique sensor responsive function, which makes the system software have a very common 'range from a few kilograms to dozens of tons. The key technology is programmable control. When the customer selects a certain type of sensor in the measurement range according to his application target, or when the sensor is replaced due to common faults (or changes in the production process), the professional technicians of engineering projects (or customer) only need to connect the sensor with the system software, according to the human-computer interaction technology page, key the command and the scope of the scene, and place the standard KG or ton component (missing code) in the system software weighing plate, then the A/D model The digital converter reads the value of mV/kg or mV/t as the base value and stores it in the EEPROM of the system software for use when weighing.

In addition, the CPU calculates and clarifies the gain value of the programmable controller gain value of the instrument and equipment amplifier AD524 according to the base value and the main parameters of the measurement range transmitted from the human-computer interaction technology system software CPU. The CPU operates the 2K resistor in the digital potentiometer X9241. Make the programmable controller gain value amplifier work under the new gain value standard, and carry out the calibration and calibration of the measuring range of the transmitter. In addition to the net weight value of the weighed object, the information also has a series of functions such as safety channel setting, base value setting, enterprise setting, gain value setting, automatic zero adjustment and default setting condition maintenance. 5.1 Main programming design The functions in the electronic multihead weigher monitoring system are all activated by the customer according to the operation panel in the human-computer interaction technology system software. Therefore, the monitoring system and the interactive system software have promised the following protocols; human-computer interaction Each function of the technical system software is set up to correspond to a byte, which is called the command word. When the operation panel performs an actual operation of a certain function, the relative command word is pushed from the human-computer interaction technology system software, and the monitoring system accepts it by means of serial interface termination (because the inspection policy system needs to implement weighing and push weighing. After the actual operation of the result, it can only be accepted by the terminating method but not by the query method), after carrying out the instruction identification 'go to the relative service item assembler.

In addition, the command word is also loaded into the EEPROM, and it becomes the state to be loaded after calibration. Update the EEPROM in the program flow, and load the EEPROM status word again after returning to the beginning of the independent program flow. After each system software startup and main parameter reset, the automatic zero-adjustment programming of the amplifier is allocated once, and the source program must jump out of the cycle weighing and start from the beginning after each time the line port is terminated. The waiting point of the termination program flow is to return to the original place of purging, so an additional flag bit 7QH is set to distinguish whether the termination interrupt is enabled or not. If it occurs, it will jump out of the weighing cycle system and reset the main parameters.”5.2 Sub-programming design-5. The XI amplifier is adjusted to half the assembler. First, the CPU selects the 4th channel of the multi-channel mold opening. The result is that the 2 input terminals of the amplifier chip are shorted and the input voltage data signal is zero, and the amplification is performed. The output value of the meter is to be adjusted——AC bias voltage. Put the drag head of X9241 on which fixed terminal of the amplifier output positive bias voltage, that is, send OOH^ to the opposite WCRC drag terminal (counting memory) and then enable A/D conversion The program flow is to add and subtract the obtained data information (more than 1FFFH) and 1FFFH (1FFFH is the output data amount when the working voltage of ADCMAX194 simulates the input flow rate of zero, and determines whether the difference is a positive number, if it is positive The number is repeated WCR plus KA/D and the actual operation of addition and subtraction, until the result of the difference is zero or it is terminated when it changes from positive to negative. 5-2.2 Sensor Sm program flow Programming design of sensor zero adjustment and amplifier The concept of zero adjustment is similar. The difference depends on; the CPU does not need to set the number to the WCR first, but immediately enables an A/D conversion to distinguish the output of the data volume and the size of 1FFFH. If it exceeds, enter the WCR and gradually add 1 to the assembler. Then enter the WCR and gradually reduce the assembler by 1.

Here, the WCR value is gradually changed in one of the two assemblers until the A/D output and 1FFFH are terminated in the near future. 5.2.3 Base value setting program flow Select the base value setting on the operation panel of the interactive technology system software and press and hold. At this time, the CPU of the monitoring system may switch to the termination solution assembler due to receiving the data signal of the application communication, and identify the acceptance in the termination solution assembler. to the system command word, and then enter the base value setting assembler.

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