RU2324899C2 - Method for nonelectrical quantities measurement by means of multiple-point instrumentation system with transfer function monitoring feature, and instrumentation system for implementation thereof - Google Patents

Abstract

FIELD: physics, instrumentation technology.

SUBSTANCE: invention refers to instrumentation technology and can be implemented for accuracy monitoring in multiple-point instrumentation systems. Distinctive feature of the method is as follows: simulator is disconnected from the system after calibration, and simulation stages driver is disconnected from inputs of simulation stages switching circuit and connected directly to one of the inputs of sensors switching circuit. Instrumentation system with transfer function monitoring feature comprises recording instrument with sensors switching units and sensor signal simulator in form of the stages driver and switching circuit similar to said system sensors switching circuit. Control inputs of simulator switching circuit are connected to corresponding control outputs of the recording instrument. This ensures specified accuracy of sensor signal measurement, reduces time required to determine transfer function factors of the instrumentation system during measurements, and provides for simpler design of signal simulator.

EFFECT: provision of specified accuracy of signal measurement, improvement of the instrument response and its design simplification.

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Description

The invention relates to measuring equipment and can be used to study measurement characteristics, metrological verification and control the accuracy of the measuring device of multi-point measuring systems.

A known method for monitoring the addresses of sensor switches according to the measured values of the deviation of the resistance of precision resistors from the reference resistor installed in the measuring device (Zubov E.G., Ilyin Yu.S., Lebedeva A.I., Harchenko A.G. Method for determining and automatic control addresses of primary converters in multichannel measuring and information systems. Proceedings of TsAGI, 1984. Issue 2219, p. 53-60). For this, in each sensor switch, two precision resistors are installed, the resistances of which differ from each other and are selected from the relation R _i = 120 ± 0.5i (i = 0, 1, 2, ..., 9) Ohms. In this ratio, 120 Ohms is the nominal resistance of the reference resistor of the measuring device. Using the algorithm described in the article, the sensor switch number is calculated from the measured values of R _i . The maximum number of switches numbered by this method is 361.

The resistors used in the known system could be used to control the operation of the measuring device over the entire range of the scale, if the values of R _i are known exactly. However, the value of R _i in the known system is set with an accuracy of 0.25 Ohms, which provides the required discreteness for finding the sensor switch number, but is completely unsuitable for monitoring the operability of the measuring device: the measuring system has an analog-to-digital converter scale of ± 2000 divisions, measurement range ± 4 , 8 Ohms, the accuracy of the system is ± 0.5%, the price of 1 division is 2.4 mOhm. In order to ensure the required accuracy of monitoring the operability of the measuring device, the resistors installed in the sensor switches must be periodically checked. For verification, the entire fleet of switches must be transported to a stand where metrological verification is carried out. This is a very time consuming procedure.

Therefore, the disadvantage of this method of monitoring the health of the measuring device is the high complexity. If, in order to reduce the labor intensity, the operability of the measuring device is controlled by two resistors installed in the sensor switch, the control will be incomplete due to the fact that all bits of the analog-to-digital converter will not be monitored. If, on the basis of the measured values of the resistance of two resistors, calculate the value of the coefficients A ₀ and A ₁ , then the error in the determination of A ₁ will be equal to

where ΔN ₁ is the random component of the error in measuring the resistance of the resistor R ₁ ,

ΔN ₂ is a random component of the error in measuring the resistance of the resistor R ₂ ,

N ₁ - the average measured value of the resistance of the resistor R ₁ in the divisions of the scale of the analog-to-digital Converter,

N ₂ is the average measured value of the resistance of the resistor R ₂ in the divisions of the scale of the analog-to-digital converter, while R ₂ > R ₁ .

Error sign depends on the sign of ΔN _1, ΔN ₂ and. If ΔN _{1 is a} positive value, and ΔN ₂ is negative, then the error δ will be with a minus sign, with opposite signs ΔN ₁ and ΔN _{2, the} error δ will have a plus sign.

The error in the determination of A ₀ will be approximately ΔN ₁ .

Thus, two resistors do not provide full control over the operability of the measuring device. To satisfy all the requirements of this control, it is necessary to have several resistors whose resistances would cover the entire measurement range. This can be achieved by subjecting at least several sensor switches to metrological verification. But in this case, the complexity of the work increases.

Known multi-point measuring system (Information-measuring system "Epure". Proceedings of TsAGI, 1981. Issue 2105, p.77-114).

The Epure system includes strain gauge bellows pressure transducers, measuring equipment, a computer system with interface matching and input-output information devices, as well as system metrological support devices — an automatic calibrator of electrical signals from tensometric bridges (a simulator of sensor signals) and an automatic pressure adjuster. The system is designed to measure pressure in wind tunnels.

The automatic pressure switch is designed for metrological verification of pressure transducers and calibration of the measuring channels of the system.

The sensor signal simulator is designed to control the metrological characteristics of the Epure measuring system and is a multi-limit automatic device that reproduces a transfer function similar to a linear tensometric bridge and sets a sequence of calibrated electrical signals to the input of the system’s sensors switch. The simulator is made according to the scheme of a digital bridge with a parallel voltage divider. A parallel voltage divider consists of conductivities that shunt one of the shoulders of the bridge using the contacts of the corresponding relays, the control signals to the windings of which come from the measuring system. The sign of the output voltage of the simulator is changed by switching the power bus of the parallel voltage divider using the relay contacts. The simulator has four output voltage limits. At each limit of the simulator, 100 command levels of the output voltage are set automatically at a command from the system with a uniform step and a transition through zero of the scale. Management of the system is carried out by computer.

A disadvantage of the known device is that it is a complex measuring device that requires a large investment of time and money for its manufacture, commissioning and maintenance of specified technical characteristics during operation. In addition, the known device can be used to simulate the signals of only bridge strain gauge sensors. In the simulator, contactless key elements cannot be used.

A known method of measuring the relative deformations of structures when connecting strain gauges to a strain gauge system (RF Patent No. 2196296, IPC G01B 7/16, 2000 - prototype).

The system includes strain gages (R _d ), a resistance store (R _m ), a simulator of strain gages signals (strain gauge), a sensor switch (CD), a measuring system module (MIS) and a computer.

The method allows to measure the relative deformation of structures when connecting strain gauges to the switches of the sensors of the measuring system in a four-wire and two-wire circuit.

In the connectors of the switches, the connecting wires are soldered in a four-wire circuit, and the output of the CD is connected to the MIS input by a cable in a four-wire circuit. CD control for alternating connection of strain gauges to MIS is carried out by the module according to the program implemented by the computer. The strain gauge signal simulator is connected in a four-wire circuit to a CD instead of strain gauges. It provides a stepwise change in the resistances of precision resistors within (R _n + 2r _l ) ± ΔR _max for a two-wire strain gauge connection circuit and R _n ± ΔR _max for a four-wire strain gauge connection circuit, where R _n is the nominal value of the resistance of the strain gauges connected to the system; r _l - the resistance value of one wire with a two-wire connection of strain gages to the sensor switch; ΔR _max - the maximum value of the increment of resistance of the strain gages corresponding to the measuring range of the system.

The simulator of strain gages signals is controlled from the MIS module according to the program of metrological verification introduced into the computer. The resistance of the reference resistor R _k , relative to which the increment of the resistance of the strain gages in the normalizing transducer of the measuring module is measured, is equal to the nominal resistance of the strain gages R _n connected to the sensor switch in a four-wire circuit. When two-wire strain gages are connected to the KD, the value of R _{k is} set equal to the sum of the nominal resistance of the strain gages R _n and the resistance value of the wires 2r _l , with which the strain gage is connected to the KD switch. The value of 2r _l is measured by the device or calculated for a specific type of sensor cables.

During measurements, the method is implemented as follows. A resistance store is connected to the sensor switch in a four-wire circuit. In the computer enter the program for recording measurement results. The channel of the switch to which the resistance store is connected is continuously interrogated, and by turning the resistance bar of the store of resistance, they achieve that the readings on the computer monitor screen become equal to zero. The measured resistance value is read from the resistance store. It is equal to the value of the resistance of the reference resistor R _k , which is installed in the normalizing transducer of the measuring module. Then the resistance store is disconnected from the switch. In its place, a sensor cable is connected for a two-wire connection of strain gages and instead of a strain gage a resistance store is connected. At the resistance store, set the resistance value equal to the resistance of the reference resistor R _k , and by rotating the plugs, they achieve that the readings on the computer monitor are equal to zero. Read the value of the measured resistance, it is equal to R _to -2r _L. Disconnect the sensor cable; a simulator of strain gages signals previously connected with metrological verification is connected to the switch in a four-wire circuit; a metrological verification program is introduced into the computer and the system is metrologically verified. According to the results of verification using a computer to calculate the conversion function y = A ₀ + A ₁ x, where x is the increment of the resistance of the resistors of the simulator of the strain gauge signals at the i-th stage; And ₀ , A ₁ - the coefficients of the transformation function.

Subsequently, the relative strain is calculated from the measurement results, therefore, only the coefficient A _{1 is} used in the calculations. The value A ₀ equal to zero is set by adjustment in the measuring module.

After performing the described operations, the simulator of the strain gages signals is disconnected from the switch and the sensor cables are connected to the switch, to which the strain gages R _d glued to the test structure are soldered. The computer intended to calculate introduced strain gage on the results of measurements of the sensors S, the magnitude of A _1, and (R -2r _{to l)} for the two-wire or four-wire R for connection _to the strain gauges, the program is introduced to measure the resistance of strain gauges increments relative to the reference resistor. Static tests of the test structure are carried out, and at each stage of its loading, the deviation of the resistance values of the strain gages from the reference resistor is measured. According to these results, using a computer to calculate the value of the relative deformation of the structure for each sensor at each stage of loading.

The proposed method is applicable to IMS, in which the increment of the resistance of the strain gauge ΔR is measured. The relative deformation of the design point at the i-th stage of loading with a four-wire connection of the strain gauge to the sensor switch is determined by the formula

where R _k is the resistance of the reference resistor,

S is the strain sensitivity of the strain gauge,

N ₀ - the indication of the system at a load equal to zero,

N _i - indication of the system at the i-th load.

The relative deformation during two-wire connection of the strain gauge to the same switch is calculated by the formula

where 2r _l is the resistance of the wires connecting the strain gauge to the sensor switch with a two-wire connection.

In the known measurement method to calculate the relative deformations from the measuring system at each stage of transformation coefficient functions used directly design loading A _1, which is determined by the metrological checking system using simulated gages signals.

The disadvantage of this method is the lack of control over the value of the coefficients of the conversion function A ₀ and A ₁ during the measurement of the strain gauge signals, which, if the values of A ₀ and A ₁ calculated from the metrological verification deviate from their actual values during the measurement of the strain gauge signals, will lead to errors in the determination of relative deformations. The magnitude of this error depends on the instability of the measuring characteristic of the system over time, as well as the consequences of uncontrolled failure of the measuring device. The error in the calculation of the relative deformation due to instability of zero and the gain of the measuring device can be determined with sufficient accuracy by the formula

where ΔA ₀ - the deviation of the zero measuring device from the value of N ₀ ,

N _i - the indication of the system at the i-th load,

ΔA ₁ - the deviation of the coefficient of the conversion function from the value of A ₁ .

Example 1. The measuring system has a scale of an analog-to-digital converter of 2000 divisions, the error of the system is 0.25%, A ₀ = 0, A ₁ = 1000 divisions / Ohm. After preparing and warming up the system, N _i = 500 divisions of the scale of the analog-to-digital converter were measured. Then, a metrological verification of the system was carried out, which gave the following results: ΔA ₀ = 5 divisions of the scale of the analog-to-digital converter, ΔA ₁ = 1 division / Ohm. According to the calculation results with a system error of 0.25%, the error in calculating the relative deformation due to instability of zero and the gain of the measuring device is δ = 1.1%. Moreover, the error from ΔA ₁ is 0.1%, and the error from ΔA ₀ is 1%. This indicates that during the measurement process it is necessary to control the value of the coefficients A ₀ and A ₁ .

If we apply the known simulator of sensor signals to monitor the magnitude of the coefficients of the conversion functions A ₀ and A ₁ during the measurement of strain gauge signals, the process will be less time-consuming and provide the required measurement accuracy.

The disadvantage of this method will be that it will take additional time to interrogate the steps of the sensor signal simulator in the polling cycle of the connected output of the sensor signal simulator to several inputs of the sensor switch and sensors connected to the other inputs of the switch. This is due to the fact that at each point (channel) of the switch, it is necessary to measure all the steps of the sensor signal simulator, since in the known signal simulators the shaper of the sensor signal simulator steps is not separated from the key elements intended for connecting these steps. For the same reason, the use of well-known imitators of sensor signals for monitoring the operability of a measuring device in the process of measuring interrogated sensors will require a change in the known algorithm for interrogating sensors.

Known multi-point measuring system (Information-measuring system "Strength". Transactions of TsAGI, 1981. Issue 2105, p.3-76 - prototype).

The system consists of subsystems. The basic subsystem is designed to measure the signals of 2000 sensors and consists of two measuring devices, to each of which the measuring outputs of the first stage switches are connected through the second-stage switch. Up to 16 switches of the first stage are connected to one measuring device. The switches are controlled by the switch management unit. The subsystem is controlled by the central control and exchange device (CCUO), the operation modes of which are set from the system console. The system includes a computer. The communication between the central control unit and the computer is carried out by means of a cable through the switching unit of subscribers from the central control unit and the communication device from the side of the computer. The system includes a simulator of sensor signals. The system is intended for measuring, collecting and presenting information about the thermal and stress-strain state of field structures during static tests.

The simulator is designed to study and control the metrological characteristics of the measuring system "Strength" and is made in the form of a device. The device allows you to simulate the signals of single strain gauges, strain gauge half bridge, strain gauge bridge and thermocouples. In the latter case, the bridge is powered by a precision DC voltage source. Such simulators can be used in multichannel systems, the corresponding channels of which provide the measurement of signals from various sensors. The simulator is a series-connected precision resistors, which, using relay contacts, are connected to circuits to simulate the signals of a single strain gauge, strain gauge half bridge, strain gauge bridge and thermocouples. So, for example, to simulate the signals of single strain gages, a chain of resistors connected in series is used, in which resistance increments are specified by shunting the corresponding resistors. Shunting is carried out by resistors using relay contacts having low resistance. The simulator is powered by a current source, which is used to power the sensors.

Control signals are applied to the relay windings. To ensure task 31 increments of resistance, five binary digits are used.

The sensor signal simulator has one common output for all increments of resistances. The output wires are soldered to the measuring connector to simulate half-bridge signals with five wires, the signals of bridges and single strain gauges with four wires, and thermocouple signals with two wires.

During the metrological verification of the subsystem, the measuring connector of the simulator is connected by cable to the measuring inputs of the switch of the sensor of the subsystem, and the control connector, to which the wires from the relay windings are connected, is connected by cable to the control unit of the switches. The operation of the sensor signal simulator is controlled by the central control unit through the control unit of the switches according to the program specified in the computer. The measured signals of the simulator go to a computer, where they are processed and the coefficients of the conversion function are calculated.

The disadvantage of a measuring system with a well-known simulator of sensor signals is that it is a complex measuring device that requires large expenditures of time and money for its manufacture, commissioning and maintenance of specified technical characteristics during operation. In this simulator, contactless switching devices cannot be used because of the large values of the resistance of such keys in the open state and their variations.

The objective of the invention is to provide a given accuracy of measurement of sensor signals by monitoring the coefficients of the conversion function of the measuring system during measurement and reducing the time taken to determine the coefficients of the conversion function of the measuring system during measurements, as well as reducing the complexity of monitoring and simplifying the design of the signal simulator for various types sensors in multipoint measuring systems.

The technical result of the invention is to reduce the time it takes to control the accuracy of measurements of sensor signals and simplify the design of a signal simulator for various types of sensors used in multi-point measuring systems, as well as reduce the complexity of control.

The solution of the problem and the technical result for the method of measuring non-electric quantities by a multi-point measuring system with monitoring of the conversion function are achieved by the fact that before measuring the sensor signals during metrological verification of the system, the output of the sensor signal simulator, consisting of a shaper and a switch of simulation steps, is connected to the controlled inputs of the system sensor switch , simulator control inputs are connected to the corresponding outputs of the system control device, measure the simulator’s needles at each stage of the simulation, the coefficients of the system conversion function are calculated according to the measurement results, after metrological verification the simulator is disconnected from the system, and the simulator of the simulation steps is disconnected from the inputs of the simulation steps switch and connected directly to one of the input connectors of the sensor switch, to the other connectors of which are connected sensors, in the process of polling the sensor signals measure the signals of the steps of the simulator shaper, by which the coefficients are calculated conversion functions of the system, compare them with the coefficients of the conversion functions obtained during metrological verification, and based on the results of evaluating their compliance with the specified tolerance, decide on the suitability of the measuring system.

The solution of the problem and the technical result in a multi-point measuring system with a control of the conversion function, consisting of a measuring and recording unit with input switches of sensors and a sensor signal simulator, are achieved by the fact that the sensor signal simulator is made in the form of a stage shaper and a switch similar to the system sensor switch in this case, each step of the shaper is connected to the corresponding input of the simulator switch, the output of which is connected to the controlled inputs of the comm utilities of the sensors of the system, and the control inputs of the simulator switch are connected to the corresponding control outputs of the measuring and recording unit.

Figure 1 presents a block diagram of a multi-point measuring system for implementing the method.

Figure 2 presents the functional diagram of a multi-point measuring system with connected to the sensor switch simulator of sensor signals.

The multi-point measuring system for implementing the method consists of a step shaper of the sensor signal simulator 1, a simulator switch 2, a sensor switch system 3 and a measuring and recording unit 4. The step shaper of the sensor signal simulator 1 is made in the form of a separate unit, which simultaneously forms all the simulation steps, each of which is connected to the corresponding input of an additionally entered sensor switch, the output of which is connected to the controlled measurement inputs of the switch and the sensors of the system, and the control inputs of the switch simulator 2 and the sensor switch 3 are connected to the corresponding control outputs of the measuring and recording unit. Shaper steps 1 and the switch simulator 2 form a simulator of sensor signals. The shaper of steps 1 is made for the corresponding type and nominal resistance of the sensors connected during the measurement to the switch 3. At the same time, the switch 2 remains the same. Schematic diagrams of switches 2 and 3 are identical. The measuring and recording unit 4 consists of a measuring device, a control device, a computer and an interface. The measuring and recording unit 4 is intended for powering sensors and a shaper of steps of a simulator of sensor signals, measuring analog sensor signals and steps for simulating sensor signals, converting analog signals to digital, transmitting measured signals in digital form via an interface to a computer, and receiving control signals through an interface from a computer and the formation of control signals by switches 2 and 3. In addition to the listed functions, the computer stores the initial data for system control and processing the results of measurements, processing and presentation of measurement results in the form of tables and graphs. The measuring and recording unit 4 is described functionally. In reality, each particular system has its own structural scheme in which the described measurement, control, interface and computer units can consist of nodes that have their own circuit diagrams and are connected in accordance with the technical documentation for the system. To implement the proposed method, all these systems are suitable if the following conditions are met: the sensor switch is designed to connect single strain gauges and strain gauge bridge sensors in a four-wire circuit (thermocouples can be connected in a two-wire circuit), for single strain gauges, the deviation of the resistance of the strain gauges and resistors of the shaper of the signal simulator steps is measured sensors relative to the resistance value of the reference resistor located in the measuring device In addition, the influence of the capacities of the communication lines on the measurement accuracy at the maximum speed of the system is excluded, for which the strain gages are powered by rectangular current pulses.

The method is as follows. Before carrying out metrological verification, the shaper of the steps of the sensor signal simulator 1 is connected to the input connector of the simulator 2 switch. The output of the switch 2 is connected to the parallel inputs of the switch 3 in the same way as when connecting the known sensor signal simulators. A metrological verification program is introduced into the computer and metrological verification of the measuring system is carried out. According to the measurement results at each stage of the simulation of the sensor signals, which forms the shaper of the stages of the sensor signal simulator 1 for each of the controlled channels of the sensor switch, the coefficients of the conversion function A ₀ and A ₁ are calculated by a known algorithm, which are stored. The output of the sensor signal simulator, consisting of driver 1 and switch 2, is disconnected from the measuring inputs of the sensor switch 3. The control inputs of the switch 2 are disconnected from the corresponding outputs of the measuring and recording unit 4.

Before carrying out measurements of the sensor signals, the shaper of the steps of the sensor signal simulator 1 is disconnected from the input connector of the switch of the simulator 2 and connected to one of the measuring connectors of the sensor switch 3, to the remaining connectors of which sensors are connected. A program is entered into the computer and the signals of the sensors connected to the measuring inputs of the switch 3 and the steps of the former 1 simulating the signals of the sensors are measured in a single polling cycle. To improve the accuracy of the measurement, it is recommended to carry out measurements not in one but in several cycles of polling the channels of switch 3. The measurement results of each cycle (cycles) process and calculate physical quantities according to the readings of the sensors, and according to the readings of the former 1 simulating the signals of the sensors, the conversion function coefficients are calculated A ₀ and A ₁ . They are compared with the same coefficients determined during the metrological verification, and if the specified tolerance is met, a decision is made on the suitability of the measuring system for the next measurement cycle.

The application of the invention will allow to control the operability of the measuring device with a given accuracy and, without changing the algorithm for polling sensors, reduce the polling time of all stages simulating sensor signals by m times, where m is the sum of the number of steps (positive, negative and zero) in the simulator of the stages sensor signals.

A multi-point measuring system with a simulator of sensor signals is presented in figure 2. An automatic sensor signal simulator consists of a signal driver of a sensor simulator 1 and a switch of a simulator 2. The stage generator of a sensor signal simulator 1 is made in the form of a separate unit, which simultaneously forms all stages of simulation. The signal generator of the simulator 1 has outputs, each of which corresponds to a certain stage of the signal increment with its own sign. Figure 2 shows a schematic diagram of a signal conditioner simulator single strain gages. The shaper consists of series-connected precision resistors R ₀ ... R _n . The resistance of the resistor R is equal to ₀ (R _n -kΔR). The resistance value R _n corresponds to the value of the nominal resistance of the strain gages connected through the sensor switch 3 to the measuring device of block 4, and the value of the reference resistor, relative to which the deviation of the resistance of the strain gage from its nominal value is measured, k is the number of negative stages imitating the sensor signals in the former 1, ΔR is the increment of the resistance of one stage. The resistance of the resistor R _{1 is} greater than R ₀ by ΔR. Each resistance of the subsequent resistor increases by ΔR. The resistance of the resistor R _n is equal to (R _n + pΔR), where p is the number of positive steps imitating the sensor signals in the former 1. If k and p are equal, the resistance of the zero step is R _n .

Each resistor R ₀ ... R _{n is} connected by wires with the corresponding pins of the connector of the former 1 according to a four-wire circuit, while the extreme wires are current, and the internal ones are potential. Each such connection forms the output of the corresponding step of simulating the strain gauge signal in the driver 1. The outputs of the signal driver 1 are connected through connectors to the measurement inputs of the switch simulator 2, the measurement output of which is the output of the signal simulator.

Figure 2 shows a diagram of a shaper of steps of a simulator of sensor signals for single strain gages. Similar shaper circuits can be created to simulate the signals of bridge strain gauge sensors of force, displacement, pressure, etc., as well as thermocouples (for thermocouples, the former 1 must be supplied with a stable DC voltage). In addition, for example, to simulate the signals of the bridge strain gauge sensors, each step of the shaper 1 can be performed according to the bridge circuit with the corresponding resistance in the shoulder of the bridge, and the power of all bridges is common: current or voltage. Moreover, all of these step shapers of the respective sensors can be connected to the same switch of the simulator 2.

The switch of the simulator 2 has a circuit diagram similar to the switches of the sensors of the measuring system. Before studying the characteristics of the system or its metrological verification, the outputs of the shaper 1 corresponding to the type and nominal resistance of the sensors that will be used during operation of the system are connected to the measuring inputs of the switch simulator 2. The output of the signal simulator, which is the output of the switch 2, is connected to the measuring inputs of the sensor switch 3. Switches 2 and 3 can be made according to a matrix or pyramidal scheme of connecting contactless key elements. Figure 2 presents as an example the switches 2 and 3, made according to the pyramidal scheme. A description of such a switch is given, for example, in a book (see Gutnikov B.C. Integrated Electronics in Measuring Devices. L., "Energy", 1980). The system usually uses several switches 3, therefore, a three-stage scheme for connecting key elements is used: the first stage is the number of the point in the switch connector (Nok), the second stage is the number of the switch connector (Nokr), the third stage is the number of the switch in the system (Nokom ) To control the selection of the required point in the switch, the control bus of the measuring system is used, which have the corresponding names: No. TK, No. RK, No. Kom. The binary code transmitted through them from the control unit of block 4 in the sensors of the system sensors is converted in the decoders of the switches into a control signal that opens the corresponding keys in the chain: the number of the specified point in each connector, the number of the required connector from all connectors, the number of the specified switch from all switches. The control inputs of the switch simulator 2 are connected to the corresponding control buses of block 4 of the measuring system. To select the number of the switch 2, the same bus numbers are used as for the switch 3, since the logical number of the switches 2 and 3 must be the same. To select the point number in the connector and the connector number in the switch 2, additional buses are used, which are named No and No respectively. The measuring output of each of the switches 3 is connected to the measuring line, which is connected to the measuring device of block 4. Figure 2 shows one sensor switch 3.

A multi-point measuring system with a simulated sensor signal operates as follows. A computer introduces a system metrological verification program. According to the program, block 4 on the bus lines No.com gives the logical number codes of the switch 2 and 3, through which the measuring output of the switch 3 is connected to the measuring line, and the measuring output of the switch 2 through the addresses of the connector points soldered in the cable is connected to the controlled measuring inputs of the switch 3, to which this cable is connected. On the No. 1 bus, the No. 4 bus, block 4 will issue codes for connecting the first of the given points of the switch 3 to the measuring bus. On the No. 1 bus and the No. 4 bus, block 4 will give codes for connecting the first point of the switch 2 to the first of the given points of the switch 3. By the created thus chain closed contactless keys resistor R ₀ to four-wire circuit is connected via a measuring line to the input of the measuring device unit 4. Carry out a predetermined number of measurements of variations in resist metrological checking program Nia resistor R ₀ of the value of the reference resistor R _n. The measured value of this deviation is (-kΔR) and represents (-k) the level of the former 1. This is the highest negative stage of the former 1. The average value is found from the measurement results of this stage. Then, on the No and No tires, block 4 will issue codes for connecting the second point of the switch 2 to the first of the given points of the switch 3. In this case, the resistor R _{1 will be} connected to the input of the measuring device of block 4 through the measuring line. The number of measurements specified in the metrological calibration program is measured for the deviation of the resistance value of the resistor R ₁ from the value of the reference resistor R _n . The measured value of this deviation is equal to: - (k-1) ΔR and represents - (k-1) stage of the former 1. The average value is found from the measurement results of this stage. Then, on the No and No tires, block 4 will issue codes for connecting the third point of the switch 2 to the first of the given points of the switch 3. In this case, a subsequent resistor will be connected to the input of the measuring device of block 4 through the measuring line. Will be measured deviations of the resistance value of this resistor from the value of the reference resistor R _n and found the value of the average value. Such an algorithm for connecting the resistors of the driver 1 and measuring the deviation of the stage resistance from the resistance R _n will continue until the resistor R _n is connected and the deviation of its resistance from R _{n is} measured. The measured value of this deviation is (+ pΔR) and represents the highest positive (+ p) step of the shaper 1. The average value is found from the results of measurements of this step. At this point, the measurements of each stage of simulation of the resistance of the sensors for the first of the given points of the switch 3 are completed. The measured average values of the deviation of the resistance value of the resistor of each stage of the former 1 from the value of the reference resistor R _n and the resistance value of each stage of the former 1, determined earlier during the metrological verification of the former 1, calculate the conversion function coefficients A ₀ and A ₁ , which are stored.

On the Noct, Nork buses, unit 4 will issue codes for connecting the second of the given points of the switch 3 to the measuring line. On the Noi and Nori buses, block 4 will give codes for connecting the first point of the switch 2 to the second of the given points of the switch 3. The following is described the cycle will be repeated until all subsequent steps of the driver 1 are polled and measured for the second of the given points of the switch 3. Using the averaged measurement results and the known resistance values of each step of the driver 1, the coefficients of the functions are calculated and stored and the transformation A ₀ and A ₁ to the second set of switch points 3.

Similarly, the measurement results will be interrogated, measured, processed, and the coefficients of the transformation function A ₀ and A _{1 will be found} for the third and all subsequent from the given points of the switch 3. The calculated coefficients of the conversion function A ₀ and A ₁ for all the given points of the switch 3 are averaged and determined by the average values coefficients A ₀ and A ₁ for the measuring device.

The application of the inventions will allow to control the operability of the measuring device with a given accuracy and, without changing the algorithm for polling sensors, reduce the polling time of all stages simulating sensor signals by m times, where m is the sum of the number of steps (positive, negative and zero) in the simulator of the stages sensor signals. In addition, the use of inventions will make it possible to unify the device for switching stages of the simulator for various types and nominal resistances of strain gauges and strain gauge sensors, thereby reducing the cost of designing, manufacturing and operating a simulator of sensor signals.

application

In this appendix, justifications for the errors given earlier in the text of the description are given.

1. The error in calculating the coefficients A ₀ and A ₁ from the measured resistances of the two resistors

We will calculate the coefficients of the conversion function A ₀ and A ₁ according to the results of measurements of the resistances of two resistors. Let the deviation of the resistance of the first resistor from the reference resistor R _k equal to ΔR ₁ , and the second resistor is equal to ΔR ₂ . Typically, when checking the accuracy of a measuring device, the values of the resistors are selected from the measured values of ΔR ₁ and ΔR ₂ so that the value of ΔR _{1 is} near zero and the value of ΔR ₂ corresponds to the measuring range of the measuring device.

Represents the values of ΔR ₁ and ΔR ₂ on the chart 1 on the abscissa, and the corresponding measurements of dimension - dividing the analog-to-digital converter of the measuring device of the scale, is plotted along the ordinate. Then the value ΔR ₁ corresponds to the value of N ₁ , and ΔR ₂ - the value of N ₂ . Draw a straight line through the coordinates ΔR ₁ , N ₁ and ΔR ₂ , N ₂ and denote it in figure ₁ by number 1. When measuring ΔR _1, the measurement result of N ₁ will differ from the true value by a random error of ± ΔN ₁ and is equal to N ₁ ± ΔN ₁ . Similarly, for ΔR _2, the measurement result is N ₂ ± ΔN ₂ . The signs of random errors ΔN ₁ and ΔN ₂ can be positive and negative.

Let ΔN ₁ be a positive value, and ΔN ₂ - negative. Draw a straight line through points N ₁ + ΔN ₁ and N ₂ -ΔN ₂ , which we denote by number 2.

If ΔN ₁ is a negative value, and ΔN ₂ is positive, then the line drawn through the points N ₁ -ΔN ₁ and N ₂ + ΔN ₂ will be number 3.

Lines 1, 2, and 3 in FIG. 1 determine the transformation function y = A ₀ + A ₁ x of the measuring system, where y corresponds to N, x to ΔR values. Obviously, if ΔR ₁ and ΔR _{2 are} measured without errors, then the coefficients A ₀ and A ₁ will be calculated accurately. If ΔR ₁ and ΔR _{2 are} measured with errors, then the coefficients A ₀ and A ₁ will be calculated with an error.

We calculate the value of this error for line 2. We denote the segment OD by z, the segment CE is N ₁ + ΔN ₁ , the segment BF is N ₂ -ΔN ₂ , the segment OE is ΔR ₁ , the segment OF is ΔR ₂ . From the similarity of triangles DBF and DCE we find

Denote the coefficient A ₁ calculated for line 2, by A ₁₂ . The coefficient A ₁₂ is equal to the ratio of the segment BF to the segment DF. Substituting the values of BF and DF in this ratio, we obtain

and substituting its value instead of z and performing the transformations, we find

The coefficient A ₁ calculated for line 1 is equal to

Define the relative error in calculating the coefficient A ₁ :

Substituting the values of A ₁₂ and A ₁ into this formula, we find

For line 3, the relative error in calculating the coefficient A ₁ is

Define the error in calculating the coefficient A ₀ for line 2.

, где отрезок LO представляет собой погрешность ΔА₀ вычисления коэффициента А₀ для прямой 2, отрезок OD обозначен через z, отрезок BF равен N₂-ΔN₂, отрезок DF равен ΔR₂+z. Подставив эти значения в приведенное соотношение, найдемFrom the similarity of triangles DBF and DLO

where the segment LO represents the error ΔА _{0 of} calculating the coefficient A ₀ for line 2, the segment OD is denoted by z, the segment BF is N ₂ -ΔN ₂ , the segment DF is ΔR ₂ + z. Substituting these values in the given ratio, we find

Taking into account the previously found values for z, having carried out the transformations, we define

When ΔR ₁ = 0, which is desirable when monitoring the measuring device for two resistors, N ₁ = 0 and ΔА ₀ = ± ΔN ₁ depending on the sign of ΔN ₁ .

2. The calculation of the error in the calculation of the relative deformation due to the instability of zero and the gain of the measuring device

Consider the formula for calculating the relative deformations with a four-wire connection of strain gauges:

where N _i , N ₀ is the measurement result, respectively, on the i-th and zero loading of the investigated design, the deviation of the resistance of the strain gauge from the resistance of the reference resistor R _k located in the normalizing transducer of the measuring device,

S is the strain gauge sensitivity.

, где А₁ и A₀ - коэффициенты функции преобразования системы, ΔA₁ и ΔA₀ - приращения этих коэффициентов соответственно из-за нестабильности коэффициента усиления и нуля.Measurements of the signals of the strain gauge installed at the point of construction begin at a load of zero. The measurement result is N ₀ . Due to the instability of zero and the gain of the measuring device of the system, the subsequent measurement result N _i will change and will be equal to

where A ₁ and A ₀ are the coefficients of the system conversion function, ΔA ₁ and ΔA ₀ are the increments of these coefficients, respectively, due to the instability of the gain and zero.

As a result of this, the formula for calculating the strain will have the following form:

Find the relative error in the calculation of the relative deformation due to the instability of zero and the gain of the measuring device:

Substituting the values ε _i0 and ε _i1 into this formula, we find:

When N ₀ = 0

The above calculations of errors confirm the correctness of the conclusions made in the description.

Claims (2)

1. The method of measuring non-electric quantities by a multi-point measuring system with monitoring the conversion function, which consists in the fact that before measuring the sensor signals during metrological verification of the system, the output of the sensor signal simulator, consisting of a shaper and a switch of simulation steps, is connected to the controlled inputs of the sensor switch of the system, control inputs the simulator is connected to the corresponding outputs of the system control device, the signals of the simulator are measured at each stage of the simulation, by coefficients of the conversion function of the system are calculated by measuring ultrasonics, characterized in that after metrological verification, the simulator is disconnected from the system, and the imager of the simulation steps is disconnected from the inputs of the switch of simulation steps and connected directly to one of the input connectors of the sensor switch, to the other connectors of which the sensors are connected, in the process the polling cycle of the sensor signals is also measured by the signals of the steps of the simulator shaper, by which the coefficients of the system conversion function are calculated we compare them with the coefficients of the conversion function obtained during metrological verification, and based on the results of evaluating their compliance with the specified tolerance, decide on the suitability of the measuring system. 2. A multi-point measuring system with control of the conversion function, consisting of a measuring and recording unit with input sensors of the system sensors and a sensor signal simulator, characterized in that the sensor signal simulator is made in the form of a stage shaper and a switch similar to the system sensor switch, each the shaper stage is connected to the corresponding input of the simulator switch, the output of which is connected to the controlled inputs of the system sensor switches, and the control inputs Switch rows simulator connected to the respective control outputs of the measuring and recording unit.

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