Sensor with improved voltage protection
A radar level gauge using microwaves for measuring a level of a surface of a product in a container, comprising a two-wire interface for connecting said measurement circuitry externally of said radar level gauge. A voltage protection circuitry connected between the two lines of the two-wire interface, the voltage protection circuitry including a transistor having an input, an output and a control terminal, a voltage regulator component connected between the output and the control terminal in such a way that the regulating characteristics of the voltage regulator component determines the voltage required to open the transistor, and a resistor connected between the control terminal and the input of the transistor.
1 . A radar level gauge using microwaves for measuring a level of a surface of a product in a container, comprising:
a microwave emitter for transmitting microwaves towards the surface and receiving microwaves reflected by the surface,
measurement circuitry arranged to determine said level based on a relation between transmitted and received microwaves,
a signal transfer medium coupled at a first end to said microwave emitter and coupled at second end to said measurement circuitry,
a two-wire interface for connecting said measurement circuitry externally of said radar level gauge, and
voltage protection circuitry connected between the two lines of the two-wire interface, said voltage protection circuitry including:
a transistor having an input, an output and a control terminal,
a voltage regulator component connected between the output and the control terminal in such a way that the regulating characteristics of the voltage regulator component determines the voltage required to open the transistor, and
a resistor connected between the control terminal and the input of the transistor.
2 . The radar level gauge in claim 1 , wherein the voltage regulator component is a regulator diode.
3 . The radar level gauge in claim 1 , wherein the voltage regulator component is an integrated circuit.
4 . The radar level gauge in claim 1 , wherein the transistor belongs to the group of power transistor, field effect transistor, MOSFET, and bipolar transistor.
5 . The radar level gauge in claim 1 , wherein said two-wire interface is arranged to provide the measurement circuit with power.
6 . The radar level gauge in claim 1 , wherein said two-wire interface is arranged to communicate an indication of said level.
7 . A sensor for gauging a process variable, comprising:
measurement circuitry arranged to perform a measurement of said process variable and to determine a value of said process variable based on said measurement,
a two-wire interface for connecting said measurement circuitry externally of said sensor, and
voltage protection circuitry connected between the two lines of the two-wire interface, said voltage protection circuitry including:
a transistor having an input, an output and a control terminal,
a voltage regulator component connected between the output and the control terminal in such a way that the regulating characteristics of the voltage regulator component determines the voltage required to open the transistor, and
a resistor connected between the control terminal and the input of the transistor.
8 . The sensor in claim 7 , wherein the voltage regulator component is a regulator diode.
9 . The sensor in claim 7 , wherein the voltage regulator component is an integrated circuit.
10 . The sensor in claim 7 , wherein the transistor belongs to the group of power transistor, field effect transistor, MOSFET, and bipolar transistor.
11 . The sensor in claim 7 , wherein said two-wire interface is arranged to provide the measurement circuit with power.
12 . The sensor in claim 7 , wherein said two-wire interface is arranged to communicate a measurement signal.
13 . A radar level gauge using microwaves for measuring a level of a surface of a product in a container, comprising:
a microwave emitter for transmitting microwaves towards the surface and receiving microwaves reflected by the surface,
measurement circuitry arranged to determine said level based on a relation between transmitted and received microwaves,
a signal transfer medium coupled at a first end to said microwave emitter and coupled at second end to said measurement circuitry,
a two-wire interface for connecting said measurement circuitry externally of said radar level gauge, and
voltage protection circuitry connected between the two lines of the two-wire interface, said voltage protection circuitry including:
a voltage regulator device having a cathode and an anode,
a first diode connected with its anode to the first line and its cathode to the cathode of the regulator device,
a second diode connected with its cathode to the second line and its anode to the anode of the regulator device,
a third diode connected with its cathode to the cathode of the first diode and its anode to ground,
a fourth diode connected with its anode to the anode of the second diode and its cathode to ground.
14 . The radar level gauge in claim 13 , wherein said voltage regulator device is a voltage regulator diode.
15 . The radar level gauge in claim 13 , wherein said voltage regulator device comprises:
a transistor having an input, an output and a control terminal,
a voltage regulator component connected between the output and the control terminal in such a way that the diode characteristics determines the voltage required to open the transistor, and
a resistor connected between the control terminal and the input of the transistor.
16 . The radar level gauge in claim 13 , wherein said first and second diodes are connected to ground via a bi-directional regulator diode.
17 . The radar level gauge in claim 13 , wherein said two-wire interface is arranged to provide the measurement circuit with power.
18 . The radar level gauge in claim 13 , wherein said two-wire interface is arranged to communicate an indication of said level.
19 . A sensor for gauging a process variable, comprising:
measurement circuitry arranged to perform a measurement of said process variable and to determine a value of said process variable based on said measurement,
a two-wire interface for connecting said measurement circuitry externally of said sensor, and
voltage protection circuitry connected between the two lines of the two-wire interface, said voltage protection circuitry including:
a voltage regulator device having a cathode and an anode,
a first diode connected with its anode to the first line and its cathode to the cathode of the regulator device,
a second diode connected with its cathode to the second line and its anode to the anode of the regulator device,
a third diode connected with its cathode to the cathode of the first diode and its anode to ground,
a fourth diode connected with its anode to the anode of the second diode and its cathode to ground.
20 . The sensor in claim 19 , wherein said voltage regulator device is a voltage regulator diode.
21 . The sensor in claim 19 , wherein said voltage regulator device comprises:
a transistor having an input, an output and a control terminal,
a voltage regulator component connected between the output and the control terminal in such a way that the diode characteristics determines the voltage required to open the transistor, and
a resistor connected between the control terminal and the input of the transistor.
22 . The sensor in claim 19 , wherein said first and second diodes are connected to ground via a bi-directional regulator diode.
23 . The sensor in claim 19 , wherein said-two-wire interface is arranged to provide the measurement circuit with power.
24 . The sensor in claim 19 , wherein said two-wire interface is arranged to communicate a measurement signal.
25 . A radar level gauge using microwaves for measuring a level of a surface of a product in a container, comprising:
a microwave emitter for transmitting microwaves towards the surface and receiving microwaves reflected by the surface,
measurement circuitry arranged to determine said level based on a relation between transmitted and received microwaves,
a signal transfer medium coupled at a first end to said microwave emitter and coupled at second end to said measurement circuitry,
a two-wire interface for connecting said measurement circuitry externally of said radar level gauge,
voltage protection circuitry connected between the two lines of the two-wire interface, said voltage protection circuitry being symmetric with respect to ground,
a first current controlled voltage regulator connected on the first line, and a second current controlled voltage regulator connected on the second line,
said voltage regulators being controlled by a regulating current flowing through the voltage barrier.
26 . The radar level gauge in claim 25 , wherein the voltage protection circuitry comprises:
a voltage regulator device having a cathode and an anode,
a first diode connected with its anode to the first line and its cathode to the cathode of the regulator device,
a second diode connected with its cathode to the second line and its anode to the anode of the regulator device,
a third diode connected with its cathode to the cathode of the first diode and its anode to ground,
a fourth diode connected with its anode to the anode of the second diode and its cathode to ground.
27 . The radar level gauge in claim 26 , wherein the voltage regulator device comprises:
a transistor having an input, an output and a control terminal,
a voltage regulator component connected between the output and the control terminal in such a way that the diode characteristics determines the voltage required to open the transistor, and
a resistor connected between the control terminal and the input of the transistor.
28 . The radar level gauge in claim 27 , where said regulating current is a threshold current through the voltage regulator component.
29 . The radar level gauge in claim 25 , wherein said two-wire interface is arranged to provide the measurement circuit with power.
30 . The radar level gauge in claim 25 , wherein said two-wire interface is arranged to communicate an indication of said level.
31 . A sensor for gauging a process variable, comprising:
measurement circuitry arranged to perform a measurement of said process variable and to determine a value of said process variable based on said measurement,
a two-wire interface for connecting said measurement circuitry externally of said sensor,
voltage protection circuitry connected between the two lines of the two-wire interface, said voltage protection circuitry being symmetric with respect to ground,
a first current controlled voltage regulator connected on the first line, and a second current controlled voltage regulator connected on the second line,
said voltage regulators being controlled by a regulating current flowing through the voltage barrier, thereby ensuring that the circuit configuration.
32 . The sensor in claim 31 , wherein the voltage protection circuitry comprises:
a voltage regulator device having a cathode and an anode,
a first diode connected with its anode to the first line and its cathode to the cathode of the regulator device,
a second diode connected with its cathode to the second line and its anode to the anode of the regulator device,
a third diode connected with its cathode to the cathode of the first diode and its anode to ground,
a fourth diode connected with its anode to the anode of the second diode and its cathode to ground.
33 . The sensor in claim 32 , wherein the voltage regulator device comprises:
a transistor having an input, an output and a control terminal,
a voltage regulator component connected between the output and the control terminal in such a way that the diode characteristics determines the voltage required to open the transistor, and
a resistor connected between the control terminal and the input of the transistor.
34 . The sensor in claim 32 , where said regulating current is a threshold current through the voltage regulator component.
35 . The sensor in claim 32 , wherein said two-wire interface is arranged to provide the measurement circuit with power.
36 . The sensor in claim 32 , wherein said two-wire interface is arranged to communicate a measurement signal.