JP5888688B1 - Two-wire signal receiver and method of using surplus voltage of two-wire signal receiver - Google Patents

Abstract

A two-wire signal receiving device detects a surplus voltage that can be used as an operating power supply voltage in its own device out of voltages received from a DC power source that generates a current signal in a pair of transmission lines, Effectively uses the surplus voltage inside the device. A two-wire signal receiver 10 measures a current value of a current signal Is transmitted to a pair of transmission lines L1, L2, and detects a surplus voltage in the pair of transmission lines L1, L2. Furthermore, the variable control operation unit 13 in the apparatus variably controls the clamp voltage Vz output from the output terminal of the variable regulator circuit unit of the variable regulator unit 11 to a predetermined voltage according to the detected surplus voltage, and the clamp voltage Vz Is input to the input terminal of the DC-DC converter unit 12 at the next stage. [Selection] Figure 1

Description

  The present invention relates to a two-wire signal receiver capable of receiving a current signal transmitted from a two-wire transmitter via a pair of transmission lines, and a surplus voltage utilization method of the two-wire signal receiver.

  Conventionally, as an example of a two-wire signal receiver that can receive a current signal transmitted from a two-wire transmitter via a pair of transmission lines, the measured physical quantity (temperature, pressure, humidity, etc.) is the same. A receiver for indicating a corresponding process variable PV is known (for example, see Patent Document 1).

  First, the configuration will be described with reference to FIG.

  FIG. 5 is a diagram showing the connection between the conventional two-wire signal transmission device 110 and the receiver 112.

  Here, the two-wire signal transmission device 110 converts this into an electric signal corresponding to a process variable PV such as temperature, pressure, and humidity, and outputs current corresponding to this process variable PV at its output terminals T101 and T102. The signal IL1 is output.

  The output terminals T101 and T102 of this two-wire signal transmission device 110 receive a power supply 111 for energizing the two-wire signal transmission device 110 and a current signal IL1 through two transmission lines Line1 and Line2 and receive the current signal IL1. A receiver 112 indicating the variable PV is connected in series.

  The current signal IL1 is transmitted as a unified current signal of 4 mA to 20 mA, for example.

  According to this configuration, the 4 mA current in the unified current signal covers all of the power consumed in the two-wire signal transmission device 110 as the base current.

  In addition, even when the current value changes in such a limited current value range of the unified current signal, the voltage between the output terminals is held almost constant and the minimum operating voltage of the circuit is maintained. There is also known a two-wire transmitter capable of covering the entire signal range of the unified current signal with a low terminal voltage to which a predetermined voltage is applied (see, for example, Patent Document 2).

  According to this configuration, since there is a margin in the voltage that can be used in the circuit, for example, an LCD display with a backlight can be provided, so that the degree of freedom in circuit design increases.

  In addition, when the current value range of the unified current signal corresponding to the process variable PV is determined by a current value in the range of 4 mA to 20 mA, for example, a lower limit current value (for example, 4 mA) is secured as the operating current inside the device itself. Therefore, the remaining 16 mA was unnecessary and was wasted in the output stage transistors. There is also known a field instrument that includes a charging unit that charges a storage battery with the heat that has been lost, and uses the stored power as a power source for peripheral circuits inside the device (see, for example, Patent Document 3). .

  On the other hand, among the unified current signals supplied from the upper system in a range of 4 mA to 20 mA, for example, the current signal exceeding the lower limit current value (for example, 4 mA) is regarded as the surplus current, and the electropneumatic that incorporates the surplus current There is also known a positioner including a current adjusting unit that distributes the coils of the conversion unit (see, for example, Patent Document 4).

  According to this configuration, the surplus current is distributed to the function circuit unit, so that the current to the function circuit unit such as the electropneumatic conversion unit is increased or the function circuit unit of the additional function such as abnormality diagnosis is operated. Is possible without sacrificing basic functionality.

  In addition, it reduces the voltage drop at the receiving resistor that detects the current signal transmitted from the external transmitter, which is supplied with power from the built-in DC power supply via two transmission lines, via the receiving resistor. A two-wire receiving instrument that can increase the power that can be used in the transmitter is also known (see, for example, Patent Document 5).

  Furthermore, even when the current signal to be transmitted has a burnout output value (for example, 3.2 mA) lower than the lower limit current value (for example, 4 mA) of the unified current signal in the range of 4 mA to 20 mA, the arithmetic control unit inside the apparatus There is also known a two-wire transmitter that can operate (see, for example, Patent Document 6).

  Japanese Patent Laid-Open No. 3-117828   Japanese Patent Laid-Open No. 5-166093   JP 2006-323476 A   JP 2012-211599 A   Japanese Utility Model Publication No. 5-39046   JP 2012-53819 A

  However, in the configuration of the conventional transmitter and receiver described above, the unified current signal transmitted from the transmitter to the receiver via the pair of transmission lines is at the lower limit current value (for example, 4 mA), and the internal configuration of its own device The basic purpose is to ensure self-operation, and a current signal exceeding the upper limit current value (for example, 20 mA) is not necessary for self-operation within the device itself. Is regarded as a surplus current and is intended to effectively use the surplus current in a self-contained manner.

  In other words, the surplus current is redirected to a different application from the self-operation within the device itself, stored, or conversely, the minimum operating voltage of the device is reduced to improve the self-operation margin in the device. By doing so, the stability of the entire measurement system connected indirectly in the pair of transmission lines is improved.

  Therefore, a measurement system system (including an associated control system system, etc.) including other specifications (agreement with other elements including the line resistance of the pair of transmission lines, the same shall apply hereinafter) connected via the pair of transmission lines, Under the measurement conditions in the field where the same applies hereinafter, the individual devices are based on the principle that at least self-operation can be ensured when the current signal is a lower limit current value (for example, 4 mA).

  Therefore, each device receives power from a DC power source via a pair of transmission lines, but considers the presence of the required voltage in other specifications over the entire loop via the pair of transmission lines. Conventionally, the technical idea (technical idea) of actively obtaining a voltage (hereinafter referred to as surplus voltage) that can be supplied from a DC power source that generates power to the individual devices and actively using the surplus voltage It was not known.

  That is, when the current value of the current signal flowing through the pair of transmission lines is the maximum value (for example, 20 mA) on the transmission device or reception device side, the voltage drop in other specifications from the voltage supplied from the DC power supply. Even if the surplus voltage at the time of subtracting is left, the presence or absence of the surplus voltage and its magnitude are not considered (detected) in advance, so that the surplus voltage is effectively used on the receiving device side There was no.

  The present invention solves the above-described problems, and a two-wire signal receiving apparatus and a two-wire signal that can receive a current signal transmitted from an external two-wire transmitter via a pair of transmission lines. A surplus voltage using method of a receiving device, wherein the variable control operation unit is a surplus that can be used as an operating power supply voltage in its own device among voltages supplied from a DC power source that generates a current signal in a pair of transmission lines. The purpose is to control the clamp voltage output from the variable regulator unit to the next stage to a predetermined voltage according to the magnitude of the voltage.

  The two-wire signal receiver according to the present invention is a two-wire signal receiver capable of receiving a current signal transmitted from an external two-wire transmitter via a pair of transmission lines, Receiving resistor, a variable regulator unit that is connected in series with the receiving resistor as seen from the external two-wire transmitter, converts the current signal to voltage and outputs the clamp voltage to the next stage, and the clamp voltage is input A DC-DC converter unit that outputs a DC voltage to the next stage, and the DC voltage output from the DC-DC converter unit is supplied as an operating power supply voltage, and the clamp voltage output from the variable regulator unit is set to a predetermined voltage value. A variable control operation unit that can be variably controlled, wherein the variable control operation unit is an operation power supply within the device itself among voltages supplied from a DC power source that generates the current signal in a pair of transmission lines. Depending on the magnitude of the excess voltage available as a voltage, variable regulator unit is characterized by variably controlling the clamp voltage to a predetermined voltage outputted to the next stage.

  As a result, it is possible to detect the presence and magnitude of the surplus voltage obtained by subtracting the voltage drop in other specifications from the voltage generated by the DC power supply in the pair of transmission lines, so that the surplus in the two-wire signal receiving apparatus. The voltage can be used effectively.

  According to the two-wire signal receiver of the present invention, the variable control operation unit outputs the control signal to the variable regulator unit while measuring the current value of the current signal flowing through the reception resistor, and the variable regulator unit outputs the control signal. The clamp voltage is gradually increased from the initial setting value in a predetermined voltage range in steps, and the magnitude of the surplus voltage is detected by detecting the change in the current value of the current signal between each voltage step. Accordingly, the clamp voltage output from the variable regulator unit may be variably controlled to a predetermined voltage.

  This facilitates detection of the presence and magnitude of the surplus voltage obtained by subtracting the voltage drop in other specifications from the voltage generated by the DC power supply in the pair of transmission lines.

  According to the two-wire signal receiving apparatus of the present invention, the variable control operation unit detects the surplus voltage when the current value of the current signal flowing through the receiving resistor reaches a predetermined maximum current value, and the magnitude thereof. Accordingly, the clamp voltage output from the variable regulator unit to the next stage may be variably controlled to a predetermined voltage.

  As a result, the surplus voltage that can be supplied by the external DC power supply as the operating power supply voltage in the signal receiving device in the pair of transmission lines is the surplus voltage when the voltage drop in the other specifications is within the maximum range. Even if the signal fluctuates in the range of 4 mA to 20 mA, for example, depending on the measured physical quantity, the influence of the current fluctuation can be reduced, so the surplus on the two-wire signal receiving device side regardless of the increase or decrease of the current value of the current signal The voltage can be used stably.

  According to the method of using surplus voltage in the two-wire signal receiving apparatus according to the present invention, a two-wire signal receiving apparatus capable of receiving a current signal transmitted from an external two-wire transmitter via a pair of transmission lines. A method of using surplus voltage, wherein a receiving resistor is a step of receiving the current signal transmitted from an external two-wire transmitter, and a variable connected in series with the receiving resistor as viewed from the external two-wire transmitter. The regulator unit converts the current signal into voltage and outputs a clamp voltage to the next stage; the DC-DC converter unit receives the clamp voltage and outputs a DC voltage to the next stage; and variable control operation The unit is supplied with the DC voltage output from the DC-DC converter unit as an operating power supply voltage, and variably controls the clamp voltage output from the variable regulator unit to a predetermined voltage value. In addition, the variable control operation unit is a variable regulator according to the magnitude of the surplus voltage that can be used as the operation power supply voltage inside its own device among the voltages supplied from the DC power supply that generates current signals in the pair of transmission lines. And a step of variably controlling the clamp voltage output to the next stage by the unit to a predetermined voltage.

  As a result, it is possible to detect the presence and magnitude of the surplus voltage obtained by subtracting the voltage drop in other specifications from the voltage generated by the DC power supply in a pair of transmission lines. Available to:

  According to the two-wire signal receiver and the method of using surplus voltage of the two-wire signal receiver according to the present invention, a DC power source that generates a current signal in a pair of transmission lines is supplied as an operating power supply voltage inside the device. A surplus voltage that can be obtained is easily obtained, and the surplus voltage can be effectively used inside the two-wire signal receiving apparatus.

The block diagram which shows the outline of the whole of a pair of transmission line in Embodiment 1 of this invention, and the outline in a 2-wire type signal receiver FIG. 1 is a block diagram showing the inside of a two-wire signal receiving apparatus in Embodiment 1 of the present invention. The flowchart which shows an example of control operation of the 2-wire type signal receiver in Embodiment 1 of this invention (A) Table showing relationship between current value Is of current signal Is with respect to clamp voltage Vz, current value change, and surplus voltage Vp, (b) Timing chart of current value of clamp voltage Vz and current signal Is before and after measurement and variable control. The figure which shows an example of the 2 wire type signal receiver which can receive the electric current signal transmitted from the 2 wire type transmitter connected to the conventional external DC power supply via a pair of transmission line

  Hereinafter, in order to describe an embodiment of the present invention, it will be described with reference to the drawings.

  (Embodiment 1)

  FIG. 1 is a configuration diagram showing an overall outline of a pair of transmission lines in Embodiment 1 of the present invention and an outline in a two-wire signal receiving apparatus, and FIG. FIG. 3 is a block diagram showing the inside of the signal receiver, FIG. 3 is a flowchart showing an example of the control operation of the two-wire signal receiver in Embodiment 1 of the present invention, and FIG. 4A shows the clamp voltage Vz. 4B is a table showing the relationship between the current value of the current signal Is, the current value change of the current signal Is, and the surplus voltage Vp. FIG. 4B shows the timing of the clamp voltage Vz and the current signal Is before and after the measurement and variable control operation. It is a chart.

  First, FIG. 1 also shows the configuration of the entire measurement system including a DC power source and other specifications connected via a pair of transmission lines L1 and L2.

  Here, the two-wire signal receiving device 10 is a two-wire placed in the field system (measurement / drive system) via a pair of transmission lines L1 and L2 (part of the extending direction is omitted by a double broken line). The current signal Is transmitted from the transmitter TD can be received. The DC power source Eb only needs to have a function of generating a current signal Is corresponding to the size of a process variable PV, which will be described later, via an external two-wire transmitter TD. Are arranged in a monitoring system (control device system) in the overall configuration and are independently connected to the outside of the two-wire signal receiving device 10.

  Further, the DC power source Eb operates other specifications connected via the pair of transmission lines L1 and L2, so that a desired rated direct current is selected according to the installed system such as about 12V, about 24V, and about 36V. Supply voltage.

  On the other hand, the two-wire transmitter TD includes, for example, a field-installed two-wire signal converter such as a head-mounted signal converter or a field-type signal converter, and is to be measured. A current signal Is (for example, a unified current signal of 4 mA to 20 mA) is sent to a pair of transmission lines L1 and L2 according to the magnitude of the process variable PV when sensing a physical quantity such as external temperature, pressure, or humidity. It is a device that transmits to other specifications that are remote through the.

  The pair of transmission lines L1 and L2 have different wiring resistances RL1 and RL2 depending on the path length, the wire diameter, the wire material, and the external environment (atmosphere) temperature. If the drive system also includes a drive system, an actuator system positioner that receives the unified current signal Is and generates a drive force according to the current value may be connected. The receiving resistor Rp is also shown as an on-site system (measurement / drive system).

  On the other hand, the two-wire signal receiving apparatus 10 according to the present embodiment has an input terminal T1 and an input terminal T2 as connection terminals for the pair of transmission lines L1 and L2, and a variable regulator section between the two input terminals. 11 and a receiving resistor Rs are connected in series.

  As is clear from FIG. 1, the variable regulator unit 11 is connected in series with the receiving resistor Rs as seen from the external two-wire transmitter TD, converts the current signal Is into a voltage, and clamps the voltage to the next stage. It has a function of outputting Vz.

  Here, if, for example, a resistance value of 250Ω is selected as the receiving resistor Rs, an electromotive force of 1 to 5 V is generated at both ends of the receiving resistor Rs when a current signal Is having a current value of 4 mA to 20 mA is received. The variable control operation unit 13 (see FIG. 2) detects the electromotive force through the terminal T5, performs predetermined signal processing therein, and then displays a numerical value on the 7-segment display 14 through the signal line CTRL2. The process variable PV corresponding to the measured physical quantity can be displayed.

  Next, with reference to FIG. 2, the two-wire signal receiving device 10 located in the monitoring system (control device system) will be described in more detail.

  As described above, between the input terminal T1 and the input terminal T2, the variable regulator circuit unit 11a of the variable regulator unit 11 and the reception resistor Rs are connected in series via the connection terminal T3, the connection terminal T4, and the connection terminal T5. Has been.

  Then, a clamp voltage Vz controlled to a predetermined voltage is output from the output terminal Vout of the variable regulator circuit unit 11a of the variable regulator unit 11, and the clamp voltage Vz is input to the input terminal Vin of the DC-DC converter unit 12 in the next stage. Has been.

  Here, a control signal for controlling the magnitude of the clamp voltage Vz is input from the variable control operation unit 13 to the adjustment terminal Vadj via the signal line CTRL1, and the clamp voltage Vz is determined according to the magnitude of the control signal. Is adjusted to a voltage lower than the voltage input from the Vin terminal by a predetermined voltage.

  Then, when the clamp voltage Vz controlled to a predetermined voltage is input to the input terminal Vin of the DC-DC converter unit 12, the output terminal Vout is connected to the operation of the subsequent variable control operation unit 13 via the connection terminal T7. A voltage for supplying a predetermined voltage (for example, 5.0V, 3.3V, 2.5V, etc.) to the power supply voltage terminal Vdd is output, and the voltage is simultaneously connected in parallel via the connection terminal T7. A predetermined voltage is supplied to the operating power supply voltage terminal Vdd of the 7-segment display 14.

  Furthermore, the variable control operation unit 13 supplies a brightness adjustment control signal to the 7-segment display 14 via the control signal line CTRL2 in accordance with the obtained surplus voltage Vp.

  Here, the variable control operation unit 13 receives, for example, an electrical signal acquired from the first input voltage terminal V1in, and performs A / D conversion on a predetermined input signal processing unit, A / D conversion unit, and the processed signal. Arithmetic logic operation processing unit that performs predetermined arithmetic logic operation processing, storage unit that stores and holds predetermined specific data and program data extracted by the operation processing unit, and a signal line indicated by a broken line with a predetermined control signal It has a built-in control unit that outputs via an output signal processing unit.

  On the other hand, the first input voltage terminal V1in of the variable control operation unit 13 is connected to the input terminal T2 via the connection terminal T5.

  Thereby, the variable control operation unit 13 can measure the current value Is (1) of the current signal Is of the pair of transmission lines L1 and L2 when the current signal Is flows through the reception resistor Rs.

  Next, referring to FIG. 3, the variable control operation unit 13 of the two-wire signal receiving apparatus 10 obtains a surplus voltage Vp that can be supplied from the DC power supply Eb (see FIG. 1) as its own operation power supply voltage. The method of using it will be described sequentially.

  First, the variable control operation unit 13 sets the clamp voltage Vz output from the output terminal Vout of the variable regulator circuit unit 11a of the variable regulator unit 11 to a predetermined initial setting value (S101).

  Next, the variable control operation unit 13 measures the current value Is (1) of the current signal Is of the pair of transmission lines L1 and L2 under the first condition where the current signal Is flows through the reception resistor Rs (S102). .

  Next, the variable control operation unit 13 performs a process of determining whether or not the measured current value Is (1) of the current signal Is is a predetermined maximum current value Is (max) (for example, 20 mA). (S103).

  If it is determined that the current value Is (1) of the current signal Is is not the predetermined maximum current value Is (max) but “NO”, the process of changing the physical quantity again (the current in the reception resistor Rs) Under the condition that the signal Is flows, the current value Is (1) of the current signal Is of the pair of transmission lines L1 and L2 is measured (S102).

  That is, as a result of the determination process (S103), if the current value Is (1) of the current signal Is does not reach the predetermined maximum current value Is (max), the current value Is (1) of the current signal Is is measured ( S102) and the determination process (S103) are repeated.

  On the other hand, in the process of changing the physical quantity, the current value Is (1) of the current signal Is becomes the predetermined maximum current value Is (max), and “YES (predetermined maximum current value)” is determined by the determination process (S103). Is determined, the variable control operation unit 13 increases the clamp voltage Vz of the variable regulator circuit unit 11a by a predetermined voltage width (for example, 1 V) (S104).

  Then, the variable control operation unit 13 measures the current value Is (2) of the current signal Is under the second condition in which the clamp voltage Vz is increased (S105).

  Next, the variable control operation unit 13 determines whether or not the current value Is (2) of the current signal Is is different from the current value Is (1) immediately before the clamp voltage Vz increases, that is, 20 mA. The process is executed (S106).

  As a result of the determination process (S106), if it is determined that the current value Is (2) of the current signal Is is the same as the current value Is (1) before the increase of the clamp voltage Vz and is “NO (same)”, then again. The variable control operation unit 13 increases the clamp voltage Vz of the variable regulator circuit unit 11a by a predetermined voltage width (for example, 1 V) (S104).

  As a result, the clamp voltage Vz output from the variable regulator circuit unit 11a gradually increases stepwise from the initial setting value with a predetermined voltage width.

  On the other hand, if the current value Is (2) of the current signal Is is determined to be “YES (different)” unlike the current value Is (1) before the increase of the clamp voltage Vz as a result of the determination process (S106), it is variable. The control operation unit 13 subtracts a predetermined margin voltage value (for example, 1 V) from the total voltage value of the voltage width increased with respect to the initial setting value of the clamp voltage Vz of the variable regulator circuit unit 11a, and obtains the surplus voltage Vp. Obtain (S107).

  That is, a predetermined margin voltage value (for example, 1V) is subtracted from the total voltage value (for example, 5V) of the increased voltage width with respect to the initial voltage value (for example, 5V) of the clamp voltage Vz of the variable regulator circuit unit 11a. Then, the voltage value is set as a surplus voltage Vp (for example, 4 V).

  Thereby, the variable control operation unit 13 can easily obtain the surplus voltage Vp that the DC power supply Eb can supply as the operation power supply voltage inside the apparatus despite the simpler configuration.

  As a result, the variable control operation unit 13 sends a control signal to the variable regulator circuit unit 11a via the control signal line CTRL1 according to the surplus voltage Vp (for example, 4V), and outputs the output terminal Vout of the variable regulator circuit unit 11a. Can be raised from an initial set value (for example, 5 V) and increased to a predetermined voltage (for example, 9 V), that is, variably controlled (S108).

  Then, when the clamp voltage Vz input to the input terminal Vin of the DC-DC converter unit 12 increases by 4V, the voltage value output from the output terminal Vout of the DC-DC converter unit 12 increases (for example, increases by 4V). Thus, the output power (product of voltage and current) can be increased.

  That is, the variable control operation unit 13 can increase the segment energization current in the internal circuit and increase the luminance by sending the luminance adjustment control signal to the seven-segment display 14 via the control signal line CTRL2.

  Next, the correspondence relationship between the current value of the current signal Is, the current value change of the current signal Is, and the surplus voltage Vp with respect to the clamp voltage Vz controlled by the variable control operation unit 13 will be described with reference to FIG. To do.

  As shown in this table, first, the clamp voltage Vz is set to a predetermined initial set value (for example, 5 V) by the control of the variable control operation unit 13.

  Then, the variable control operation unit 13 measures the current signal Is to obtain the current value Is (1) (for example, 18 mA).

  If the measured current value Is (1) is a predetermined maximum current value (for example, 20 mA), the process proceeds to the next process.

  Next, under the control of the variable control operation unit 13, the clamp voltage Vz is gradually increased with a voltage width of 1V, and the current signal Is is measured each time to obtain the current value Is (2).

  If a current value Is (2) of the current signal Is that is different from the current value Is (1) before the clamp voltage Vz is increased (for example, 17 mA), the current value change at that time is measured. That is, the current value change detected between the voltage steps is 3 mA, and a surplus voltage Vp (for example, 4 V) corresponding to the change is obtained.

  Next, a timing chart before and after the measurement and before and after the variable control (rising control) will be described with reference to FIG. 4B, in which the current value of the current signal Is is indicated by a broken line and the clamp voltage Vz is indicated by a solid line.

  Before the measurement START, the clamp voltage Vz is set to a predetermined initial setting value (for example, 5V), but after the measurement START, the clamp voltage Vz gradually increases in a stepped manner with a predetermined voltage width (for example, 1V). .

  After the variable control START, a surplus voltage Vp (for example, 4 V) that can be supplied by the DC power source Eb as an operation power supply voltage inside the apparatus has already been obtained. Therefore, the clamp voltage Vz (for example, the surplus voltage Vp added) 9V), that is, variable control, that is, upward control.

  That is, before the measurement START, the clamp voltage Vz of the variable regulator circuit unit 11a is maintained at the initial setting value of 5V, and the current consumption of the 7-segment display 14 operates with the initial current.

  However, after the variable control, the clamp voltage Vz of the variable regulator circuit unit 11a is set to 9V. As a result, the operation power supply voltage terminal of the 7-segment display 14 output from the output terminal Vout of the DC-DC converter unit 12 Even if Vdd is set to a predetermined voltage (for example, 5.0 V), for example, 0.016 W (corresponding to the product of 4 mA of the base current and the increase of 4 V of the clamp voltage Vz) is newly consumed as power consumption. Available. As a result, the luminance adjustment control signal via the signal line CTRL2 is increased (supplied) by an amount equivalent to 3.2 mA as the luminance setting energization current via the terminal T7, and the 7-segment display 14 is greatly increased. Can increase brightness.

  The technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. The technical scope disclosed in different embodiments, respectively. Modifications of the embodiment obtained by appropriately combining the means are also included in the technical scope of the present invention.

  For example, a DC power source that generates a current signal via a pair of transmission lines is disposed in a monitoring system (control device system) in the overall configuration, and is independently provided outside the two-wire signal receiving device according to the present invention. However, it is only necessary to be in the loop of a pair of transmission lines. For example, it may be arranged in the field system (measurement / drive device system) or stored inside the two-wire signal receiving device. It may also be stored inside another specification (element).

  The predetermined maximum value Is (max) of the current signal Is is, for example, an upper limit value (20 mA) if the unified current signal is in the range of 4 to 20 mA, for example, depending on the physical quantity to be measured and the actual measurement value. Is most preferable, but it may be a value close to the upper limit, and may be appropriately set from a practical aspect.

  Further, in order to obtain the surplus voltage Vp, the method of setting the current signal Is to a predetermined maximum current value Is (max) may be forcibly executed manually or automatically on the two-wire transmitter TD side in advance. Alternatively, the process may be automatically executed after detecting that the current signal Is has reached the maximum value during the normal operation by the program stored in the variable control operation unit.

  Further, even if the current signal Is is not the predetermined maximum value Is (max), the clamp that is output by the variable regulator unit under each of two conditions in which the current value of the current signal transmitted from the external two-wire transmitter is different. The voltage is gradually increased from the initial setting value in a stepwise manner with a predetermined voltage width, and a change in the current value of the current signal between each voltage step is detected to supply power from a DC power source that generates a current signal to a pair of transmission lines. Of the received voltage, the magnitude of the surplus voltage that can be used as the operating power supply voltage inside the apparatus may be obtained.

  As described above, the 2-wire signal receiving apparatus and the surplus voltage using method of the 2-wire signal receiving apparatus according to the present invention are transmitted from an external 2-wire transmitter that is supplied with power from a DC power supply. In a two-wire signal receiving apparatus capable of receiving a current signal via a pair of transmission lines, the variable control operation unit obtains a surplus voltage that can be supplied by the DC power supply as an operation power supply within the apparatus itself, and further 2 Since it can be effectively used in the linear signal receiving device, it is useful as a two-wire signal receiving device and a method of using surplus voltage in the two-wire signal receiving device.

10 2-wire signal receiver 11 Variable regulator unit 11a Variable regulator circuit unit 12 DC-DC converter unit 13 Variable control operation unit 14 7-segment display PV Process variable TD 2-wire transmitter Eb DC power supply L1, L2 A pair of transmissions Lines RL1, RL2 Wiring resistances Rs, Rp of the pair of transmission lines Reception resistances T1, T2 Input terminals T3, T4, T5, T6, T7, T8 Connection terminal Is Current signal Vin Input terminal V1in First input voltage terminal V1in (min) Minimum operating voltage Vout of variable control operation section Output terminal Vdd Operating power supply voltage terminal Vadj Adjustment terminal Vp Surplus voltage Vz Clamp voltage Vss Negative power supply CTRL1, CTRL2 Signal line

Claims (4)

A two-wire signal receiver capable of receiving a current signal transmitted from an external two-wire transmitter via a pair of transmission lines,
A receiving resistor for receiving the current signal;
A variable regulator unit that is connected in series with the receiving resistor as viewed from the external two-wire transmitter, converts the current signal into a voltage, and outputs a clamp voltage to the next stage;
A DC-DC converter unit that receives the clamp voltage and outputs a DC voltage to the next stage;
The DC voltage output from the DC-DC converter unit is supplied as an operating power supply voltage, and a variable control operation unit capable of variably controlling the clamp voltage output from the variable regulator unit to a predetermined voltage value,
The variable control operation unit, according to the magnitude of the surplus voltage that can be used as the operation power supply voltage inside its own device among the voltages supplied from the DC power supply that generates the current signal to the pair of transmission lines, A two-wire signal receiving apparatus, wherein the variable regulator unit variably controls the clamp voltage output to the next stage to a predetermined voltage. The variable control operation unit outputs a control signal to the variable regulator unit while measuring a current value of the current signal flowing through the reception resistor, and sets a clamp voltage output from the variable regulator unit from a preset value to a predetermined value. The variable regulator unit detects the magnitude of the surplus voltage by gradually increasing the voltage width in steps, and detecting the change in the current value of the current signal between each voltage step, and the variable regulator unit according to the magnitude of the surplus voltage 2. The two-wire signal receiving apparatus according to claim 1, wherein the clamp voltage output from the signal is variably controlled to a predetermined voltage. The variable control operation unit detects the surplus voltage when the current value of the current signal flowing through the reception resistor reaches a predetermined maximum current value, and the variable regulator unit performs the next operation according to the magnitude. 3. The two-wire signal receiving apparatus according to claim 1, wherein the clamp voltage output to the stage is variably controlled to a predetermined voltage. A method of using surplus voltage of a two-wire signal receiver capable of receiving a current signal transmitted from an external two-wire transmitter via a pair of transmission lines,
A receiving resistor receiving the current signal transmitted from the external two-wire transmitter; and
A variable regulator connected in series with the receiving resistor as seen from the external two-wire transmitter, converting the current signal into a voltage and outputting a clamp voltage to the next stage;
The DC-DC converter unit receives the clamp voltage and outputs a DC voltage to the next stage;
The variable control operation unit is supplied with the DC voltage output from the DC-DC converter unit as an operation power supply voltage, and variably controls the clamp voltage output from the variable regulator unit to a predetermined voltage value. Including
Furthermore, the variable control operation unit, according to the magnitude of the surplus voltage that can be used as the operation power supply voltage inside its own device among the voltages supplied from the DC power supply that generates the current signal in the pair of transmission lines, Variably controlling the clamp voltage output to the next stage by the variable regulator unit to a predetermined voltage;
A method for using surplus voltage in a two-wire signal receiving apparatus.

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