RU2646311C1 - Signal transmission system from sensors with analogue output for the two-wireless communication line - Google Patents

Abstract

FIELD: data processing.

SUBSTANCE: invention relates to signaling devices. For this purpose, a signal transmission system is proposed; it comprises a sensor with an analog output, which output is connected to an input of an impedance element, whose output is connected to the sensor supply terminal, the ends of the wires of the two-wire communication line are connected to the first and second contacts of the receiving unit that contains a current collector resistor, as well as a constant voltage source, whose negative bus is the common bus of the receiving node, and the first end of the second wire of the two-wire communication line is connected to the common terminal of the sensor, receiving unit comprises a current collector amplifier whose inputs are connected to the first and second terminals of the current collector resistor which are connected respectively to the positive bus of the constant voltage source and the first contact of the receiving unit whose second contact is connected to the common bus, output of the current collector amplifier is the signal output, and the sensor power output is connected to the output of the voltage regulator, the common output and input of which are connected to the common output of the sensor and the first end of the first wire.

EFFECT: increased reliability, expanded scope of use and fail-free operation.

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Description

The present invention relates to devices for transmitting signals from analog sensors to a measuring system and can be used in stationary complexes for continuous monitoring of such quantities as vibration, pressure, angular velocity, pressure pulsations, sound, dynamic forces, changes in magnetic and electric fields, etc. which use microelectronic sensors of physical quantities based on MEMS (microelectromechanical systems) technologies with an analog output.

Many primary measuring converters of physical quantities into electrical signals can be connected to measuring equipment via a two-wire line. This requires a minimum number of connecting wires, but the absence of signal formation in the immediate vicinity of the primary measuring transducer when transmitting over a considerable distance does not provide satisfactory noise immunity. The use of built-in electronics in the sensor provides improved parameters, but may require additional power buses, which increases the cost of the number of connecting lines and the number of contacts of the input connectors (terminal blocks) of the measuring equipment, reducing its reliability and increasing dimensions and cost.

Currently, a large number of vibration, pressure, magnetic field, temperature, and the like sensors are produced, made using MEMS technology, having a common output, power output, and output of an analog signal, the signal magnitude of which linearly depends on the measured physical quantity and at zero external influences having a voltage close to or equal to half the supply voltage. The interface, called ratiometric, of such a sensor requires a three-wire connection, which limits the possibility of their use in distributed control systems, since it requires a large number of contact connections in connectors or terminal blocks, a large number of wires, which increases the size and cost of systems and increases the likelihood of failures.

Known systems for transmitting signals from sensors with an analog output (for example, vibrations — accelerometers, or acoustic signals — microphones) with signal and power transmission via a two-wire line corresponding to the IEPE interface and its analogs. In this interface, a measuring device uses a direct current generator, powered from a constant voltage source and connected through the first wire to the power / signal output, and the second wire of the communication line is common [Felix Levinzon. Piezoelectric Accelerometers with Integral Electronics. Springer, 2015 edition (August 6, 2014), 169 pages]. The disadvantage of this system is the need to use a relatively large supply voltage (usually about 24 volts), which even with a low value of the supply current (2 mA) leads to significant power consumption, reduces reliability due to the need to use elements designed for high voltage, and poorly consistent with typical power requirements for sensors made by MEMS technology. In addition, a minimum supply current of 2 mA is often insufficient to power MEMS sensors. The output voltage of the sensor in the absence of a signal of the order of 10-14 Volts and when the supply voltage is higher than the specified value, for example, if the current generator is damaged or an installation error, causes damage to the sensor. The operation of sensors of this type is based on a change in the resistance in the direct current circuit, proportionally to the measured value and transmission through the communication line of the voltage generated at the output of the analog signal transmission system.

A known solution is the transmission of sensor signals with an analog output via a two-wire line, in which the signal is transmitted along the signal line to the signal receiver, moreover, on the signal receiver side, the signal transmission line is connected to the input of the signal receiver via a capacitor, and the common bus of the signal receiver is connected to the common sensor bus [ Patent US 3356868, NPK 310/3187, IPC G01P 15/09; H03F 3/70, prior. 1963, publ. 1967]. The disadvantage of this solution is the need to use a power source integrated in the sensor.

Known systems for transmitting signals from sensors with an analog output using sensors with an integrated matching amplifier that connects to the signal receiver with a three-wire communication line that includes a common bus, power bus and signal transmission bus [Patent US 3389276, NPK 310/319, IPC G01P 09/15, prior. 1965, publ. 1968].

The disadvantage of this solution is the need to use a three-wire communication line, which significantly increases the cost of them.

Known systems for transmitting signals from sensors with an analog output, which use sensors with signal transmission over a two-wire line, containing a sensing element connected to a matching amplifier that converts the signal of the sensing element into a change in resistance connected between the output and the common bus of the signal transmission line, which in the receiver is connected through a current-sensing resistor to the bus of the power source and to the input of the matching receiving amplifier. [Patent US 3400284, NPK 310/319, IPC G01P 15/09, prior. 1966, publ. 1968, as well as RE 28596 US, NPK 310/319, IPC G01P 15/09, prior. 1973, publ. 1975].

The disadvantages of such solutions are the need to use current-sensing elements, such as resistors, in the receiver of a sufficiently high nominal value, which leads to the need to increase the required voltage of the common power source, and hence the use of relatively high-voltage elements having an increased cost, size, and reduced reliability.

Similar properties and disadvantages are inherent in technical solutions corresponding to the IEPE interface and its analogues: ICP, Izotron, Deltatron, Piezotron, etc.

Known systems for transmitting an analog signal through a two-wire communication line in the form of a current signal (current loop), in which the sensor is powered by a positive bus of a constant voltage source, and the sensor has a controlled current generator, the current of which depends on the signal of the primary measuring transducer, and the output of the controlled generator current is connected through the second wire of the two-wire communication line to the first terminal of the current-receiving resistor, the second terminal of which is connected to the negative bus of the power source in by me parts of the system [Patent US 4178525, NPK 310/319, IPC G01P 15/09, prior. 1978, publ. 1979, and also: “XTR115 XTR116. 4-20 mA Current loop transmitters. Texas Instruments, 2003 "].

The disadvantage of such a system is the need to use a relatively high supply voltage, a strict restriction on the magnitude of the voltage and supply current of the primary measuring transducer, for example a MEMS sensor. In addition, both connecting conductors are not connected to the common bus of the measuring device and the constant voltage power supply, which requires the introduction of an additional input contact for connecting the screen if the two-wire line is shielded to ensure satisfactory noise immunity. The power consumption is significantly higher even in comparison with the sensor and the transmission system via the IEPE interface.

The present invention provides for the transmission of the supply voltage via a two-wire line with the desired, relatively low, voltage value close to the supply voltage of the electronics of the primary measuring transducer (sensor) and transmission of the analog signal by changing the current value in the two-wire communication line by regulating the current in the sensor output circuit. This reduces the requirements for the value of the supply voltage and ensures the use of common buses of the output circuits to which the sensor is connected. In other words, the proposed solution provides a combination of the advantages of signal transmission over a two-wire line in the form of current changes in the current loop, in which the receiver does not require the use of a sensor driver, and the IEPE (Integrated electronics piezoelectric) interface are other synonyms: ICP, Deltatronic, Piezotronic and the like, which allow implementing the formation of the output signal at the expense of a controlled resistor in the source of the transmitted signal and which transmit the signal in the form of voltage changes, but require use in the receiving a node of the DC power generation circuit.

The proposed solution allows the use of common power in the transmitting and receiving parts, for example 5 volts or 3.3 volts and below, typical for a modern electronic base.

Closest to the proposed one is a system for transmitting signals from sensors with an analog output via a two-wire line, comprising a sensor with an analog output, the output of which is connected to the input of an impedance element, the output of which is connected to a sensor power output with an analog output, the ends of the first and second wires of a two-wire communication line connected to the first and second contacts of the receiving node, which contains a current-receiving resistor, as well as a constant voltage source, the negative bus of which is a common bus many nodes, and the first end of the second wire of a two-wire communication line is connected to a common output of the sensor with an analog output [Patent US 2012/001328 A1, IPC G01B 7/14, NKI 324 / 7.15, prior. 2010, publ. 01/19/2012].

The disadvantage of this device is its relatively low cost-effectiveness, since it requires a relatively high supply voltage, which ensures the operation of a direct current source also used in the receiving unit, and relatively low reliability, since its implementation requires the use of elements designed for this increased supply voltage . At the same time, a relatively high constant bias voltage is present on the signal transmission line, which requires the use of elements designed for this increased voltage at the output of the signal transmitting node and at the input of the receiving node, which limits the possibility of using elements designed for low-voltage power, which limits the scope of such solutions for dimensions, weight, cost and reliability.

In addition, if you are using a node with controlled resistance in the receiving node, you must use a current source to power the sensor, and if you do not use a current source in the receiving node, you must use a current controller as a node with controlled resistance (fig. 3A), both of which options require a significant increase in supply voltage.

The elimination of these disadvantages is ensured by the fact that in a signal transmission system from sensors with an analog output via a two-wire line containing a sensor with an analog output, the output of which is connected to an input of an impedance element, the output of which is connected to a sensor power output with an analog output, on a two-wire communication line, the ends of the wires are connected to the first and second contacts of the receiving node, which contains a current-receiving resistor, as well as a constant voltage source, the negative bus of which is a common bus the receiving node, and the first end of the second wire of the two-wire communication line is connected to the common output of the sensor with an analog output, the receiving node further comprises a current-receiving amplifier, the inputs of which are connected to the first and second terminals of the current-receiving resistor, which are connected respectively to the positive bus of the DC voltage source and the first contact receiving node, the second contact of which is connected to a common bus, the output of the current-receiving amplifier is a signal output, and the sensor power output with an analog output connected to the output of the voltage regulator, the common output and input of which are connected respectively to the common output of the sensor with an analog output and the first end of the first wire of a two-wire communication line.

Another difference is that in a system for transmitting signals from sensors with an analog output via a two-wire communication line, the DC voltage source contains a shunt capacitor that is connected to the positive and negative buses of this source.

Another difference is that in a system for transmitting signals from sensors with an analog output via a two-wire line, the impedance element is made in the form of a resistor.

Another difference is that in a system for transmitting signals from sensors with an analog output via a two-wire line, the impedance element is made in the form of a passive low-pass filter.

The proposed solution is illustrated by drawings.

In FIG. 1 shows a block diagram of a system.

In FIG. 2-4 shows the structural diagrams of some impedance elements that implement the function of a passive low-pass filter.

The system for transmitting signals from sensors 1 with an analog output over a two-wire communication line 2 contains a sensor 1 with an analog output, the output of which is connected to the input of an impedance element 3, the output of which is connected to the power output of the sensor 1 with an analog output, at a two-wire communication line 2, the ends of the wires 4 and 5 are connected to the first 6 and second 7 contacts of the receiving node 8, which contains a current-receiving resistor 9, as well as a DC voltage source 10, the negative bus of which is a common bus 11 of the receiving node, and the first end of the second the wires of the two-wire communication line 2 is connected to the common output of the sensor 1 with an analog output, the receiving unit further comprises a current-receiving amplifier 12, the inputs of which are connected to the first and second terminals of the current-receiving resistor 9, which are connected respectively to the positive bus of the DC voltage source 10 and the first contact 6 of the receiving node 8, the second contact 7 of which is connected to a common bus 11, the output of the current-receiving amplifier 12 is a signal output 13, and the power output of the sensor 1 with an analog output is connected to the output of a voltage balancer 14, the common terminal and input of which are connected respectively to the common terminal of the sensor 1 with an analog output and the first end of the first wire 4 of the two-wire communication line 2.

The DC voltage source 10 may include a shunt capacitor 15, which is connected to the positive and negative buses of this source 10.

In the simplest case, the impedance element 3 can be made in the form of a resistor.

To suppress, for example, high-frequency resonances of the sensor 1, the impedance element 3 can be made in the form of a passive low-pass filter.

Shown in FIG. 2, the implementation of the impedance element 3 is implemented using a resistor 16 and a capacitor 17, and a resistor 16 is connected between the input and output of the impedance element 3, and a capacitor is connected between its output and the common bus 11.

Shown in FIG. 3, the implementation of the impedance element 3 is implemented using a resistor 16, an additional resistor 18 and a capacitor 17, and the resistor 16 and the additional resistor 18 are connected in series and connected between the input and output of the impedance element, and the capacitor is connected between the common contact of the resistor 16 and the additional resistor 18 and the common tire 11.

Shown in FIG. 4, the implementation of the impedance element 3 is implemented using a resistor 16 and an inductance 19, which are connected in series and connected between the input and output of the impedance element 3.

The system for transmitting signals from sensors with analog output via a two-wire line works as follows.

A sensor 1 with an analog output converts a controlled physical quantity into an analog electrical signal, such as a charge or voltage. This signal is supplied to element 3, which converts this signal changes the total current flowing through communication line 2.

If in systems with the IEPE interface through the node 3 and the rest of the circuit, a constant current flows from the current generator in the receiving node 3, and in systems with the “current loop” interface, the constant voltage applied to the input part is accompanied by a change in current due to the use of the built-in controlled current generator, in the proposed device can vary within relatively small limits, both the current and the voltage of the sensor.

Changes in the sensor supply voltage in the proposed device are relatively small, since this voltage differs from the voltage of the source 10 by the magnitude of the drop on the current-receiving resistor 9, the typical value of which for current-receiving amplifiers 12 does not exceed several Ohms. Since the gain of the current-receiving amplifier 12 is usually very significant, the output signal at the output 13 is quite large.

For the circuit shown in FIG. 1, the magnitude of the current generated for transmission through the line is determined by the sum of the current consumption of the actual sensor 1 with an analog output and current through the impedance element 3.

Since the voltage changes transmitted through the communication line are small, the supply voltage to the sensor 1 is sufficient for its normal functioning. To ensure greater stability of characteristics, a voltage stabilizer 14 is used in the circuit. To provide better performance, this stabilizer can be designed as having a low internal drop (LDO) between input and output.

In contrast to using the IEPE interface, for which it is unacceptable to directly connect the common bus for transmitting power and signal to the power bus of the receiving node, leading to damage to the circuit, the proposed solution uses such a mode as the main working one. The absence of a current generator or current generator in the receiving node 8 of the signal source, which is typical for the current loop interface, reduces power loss. In addition, if in the IEPE interface the signal source transmitted through the signal transmission line has a relatively low internal resistance, which provides high noise immunity, although the input impedance of the receiving node is large. Or in the interface of the current loop, for which a typically low input impedance, providing increased noise immunity, although the output impedance of the current signal source is high, the proposed solution is characterized by low internal resistance for interference both from the source and the signal receiver, which provides increased noise immunity.

The proposed solution provides the ability to work with a supply voltage of source 10 at, for example, +5 or +3.3 volts and for its implementation does not require the use of elements with an operating voltage above the specified ones. This allows you to significantly expand its scope, increase reliability and reduce cost and dimensions, since elements with low operating voltage are cheaper, more reliable, smaller in size and weight.

Claims (4)

1. A system for transmitting signals from sensors with an analog output via a two-wire line, comprising a sensor with an analog output, the output of which is connected to an input of an impedance element, the output of which is connected to a sensor power output with an analog output, on a two-wire communication line, the ends of the wires are connected to the first and second the contacts of the receiving node, which contains a current-receiving resistor, as well as a constant voltage source, the negative bus of which is the common bus of the receiving node, and the first end of the second wire is two-wire the communication line is connected to a common output of the sensor with an analog output, the power output of which is connected to the first end of the first wire of the two-wire communication line, characterized in that the receiving node further comprises a current-receiving amplifier, the inputs of which are connected to the first and second terminals of the current-receiving resistor, which are connected respectively with the positive bus of the DC voltage source and the first contact of the receiving unit, the second contact of which is connected to the common bus, the output of the current-receiving amplifier is the output m of the signal, and the power output of the sensor with an analog output is connected to the output of the voltage regulator, the common output and input of which are connected respectively to the general output of the sensor with an analog output and the first end of the first wire of a two-wire communication line. 2. A system for transmitting signals from sensors with an analog output over a two-wire line according to claim 1, characterized in that the DC voltage source contains a shunt capacitor that is connected to the positive and negative buses of this source. 3. A system for transmitting signals from sensors with an analog output over a two-wire line according to claim 1, characterized in that the impedance element is made in the form of a resistor. 4. A system for transmitting signals from sensors with an analog output over a two-wire line according to claim 1, characterized in that the impedance element is made in the form of a passive low-pass filter.

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