Current detection circuit and laser system

Abstract

The application relates to a current detection circuit and a laser system, the current detection circuit comprising a first subtraction operation circuit, a voltage follower circuit, a second subtraction operation circuit and a voltage regulation circuit; an input end of the first subtraction operation circuit is configured to access a current signal, an output end of the first subtraction operation circuit is connected to a first input end of the second subtraction operation circuit; an input end of the voltage follower circuit is configured to access a first control signal, an output end of the voltage follower circuit is connected to a second input end of the second subtraction operation circuit; the output end of the voltage follower circuit is connected to a first input end of the voltage regulation circuit, a second input end of the voltage regulation circuit is configured to access a second control signal, and an output end of the voltage regulation circuit is configured to output a voltage signal. The circuit can improve the adaptability of a host computer to different current range sensors.

Description

Technical Field

[0001] This application relates to the field of electronic circuit technology, and in particular to a current detection circuit and a laser system. Background Technology

[0002] With the development of electronic circuit technology, current detection circuits adapted to laser systems have emerged. In particular, if a current-type conductivity sensor is added to the cooling equipment side of the laser system, the host computer cannot directly detect the current signal. The sensor circuit adapted to the equipment needs to convert the current signal into a voltage signal.

[0003] However, the current detection circuit in traditional technology can only be adapted to a fixed current range, or it requires additional adjustment of the zero position or the maximum value through a mechanical potentiometer, resulting in poor compatibility between the sensor and the host computer, and the host computer cannot adapt to sensors with different current ranges. Utility Model Content

[0004] Therefore, it is necessary to provide a current detection circuit and laser system that can improve the adaptability of the host computer to sensors with different current ranges, in order to address the above-mentioned technical problems.

[0005] In a first aspect, a current detection circuit is provided, the circuit comprising: a first subtraction operation circuit, a voltage follower circuit, a second subtraction operation circuit, and a voltage regulation circuit; The input terminal of the first subtraction circuit is configured to receive a current signal, and the output terminal of the first subtraction circuit is connected to the first input terminal of the second subtraction circuit. The input terminal of the voltage follower circuit is configured to receive the first control signal, and the output terminal of the voltage follower circuit is connected to the second input terminal of the second subtraction circuit. The output of the voltage follower circuit is connected to the first input of the voltage regulator circuit. The second input of the voltage regulator circuit is configured to receive a second control signal, and the output of the voltage regulator circuit is configured to output a voltage signal.

[0006] In some embodiments, the first subtraction circuit includes a first operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, and a fifth resistor; wherein, One end of the first resistor is connected to one end of the second resistor and is configured to be connected to the positive terminal of the current signal. The other end of the second resistor is connected to one end of the fourth resistor and the non-inverting input terminal of the first operational amplifier. The other end of the fourth resistor is connected to analog ground. The other end of the first resistor is connected to one end of the third resistor and is configured to be connected to the negative terminal of the current signal. The other end of the third resistor is connected to one end of the fifth resistor and the inverting input terminal of the first operational amplifier. The other end of the fifth resistor is connected to the output terminal of the first operational amplifier.

[0007] In some embodiments, the second resistor, the third resistor, the fourth resistor, and the fifth resistor have the same resistance value.

[0008] In some embodiments, the voltage follower circuit includes a second operational amplifier, a first digital potentiometer, and a sixth resistor; wherein... The A terminal of the first digital potentiometer is connected to the analog power supply, the B terminal of the first digital potentiometer is connected to one end of the sixth resistor, the AD0 terminal of the first digital potentiometer is connected to digital ground, the W terminal of the first digital potentiometer is connected to the non-inverting input terminal of the second operational amplifier, the VDD terminal of the first digital potentiometer is connected to the digital power supply, the GND terminal of the first digital potentiometer is connected to digital ground, and the SCL and SDA terminals of the first digital potentiometer are configured to receive the first control signal transmitted via the I2C bus. The inverting input of the second operational amplifier is connected to the output of the second operational amplifier and the non-inverting input of the second subtraction circuit, and the other end of the sixth resistor is connected to digital ground.

[0009] In some embodiments, the second subtraction circuit includes a third operational amplifier, a seventh resistor, an eighth resistor, a ninth resistor, and a tenth resistor; One end of the seventh resistor is connected to the output of the voltage follower circuit, and the other end of the seventh resistor is connected to one end of the ninth resistor and the non-inverting input of the third operational amplifier. One end of the eighth resistor is connected to the output of the first subtraction circuit, and the other end of the eighth resistor is connected to one end of the tenth resistor and the inverting input of the third operational amplifier. The other end of the tenth resistor is connected to analog ground, and the other end of the ninth resistor is connected to the output of the third operational amplifier.

[0010] In some embodiments, the resistance values ​​of the seventh, eighth, ninth, and tenth resistors are the same.

[0011] In some embodiments, the voltage regulation circuit includes a fourth operational amplifier, a second digital potentiometer, and a twelfth resistor; wherein... Terminal A of the second digital potentiometer is connected to terminal W of the second digital potentiometer and the output terminal of the fourth operational amplifier. Terminal B of the second digital potentiometer is connected to the inverting input terminal of the fourth operational amplifier and one end of the twelfth resistor. Terminal AD0 of the second digital potentiometer is connected to the digital power supply. Terminal VDD of the second digital potentiometer is connected to the digital power supply. Terminal GND of the second digital potentiometer is connected to the digital ground. Terminals SDA and SCL of the second digital potentiometer are configured to receive a second control signal transmitted via the I2C bus. The non-inverting input of the fourth operational amplifier is connected to the output of the second subtraction circuit, and the other end of the twelfth resistor is connected to analog ground.

[0012] In some embodiments, the circuit further includes an eleventh resistor; wherein... One end of the eleventh resistor is connected to the output of the second subtraction circuit, and the other end of the eleventh resistor is connected to the non-inverting input of the fourth operational amplifier.

[0013] In some embodiments, the current detection circuit further includes a host computer, which is connected to the input terminal of the voltage follower circuit, the second input terminal of the voltage regulation circuit, and the output terminal of the voltage regulation circuit.

[0014] Secondly, a laser system is provided, comprising a cooling device, a current-type conductivity sensor, a host computer, and a current detection circuit according to any one of the components in the first aspect; wherein, The refrigeration equipment is connected to a current-type conductivity sensor, which is connected to a current detection circuit, which is connected to a host computer.

[0015] The aforementioned current detection circuit and laser system, on the one hand, can flexibly adjust the resistance value of the voltage follower circuit through the first control signal, thereby changing the voltage signal output by the voltage follower circuit. Since the second subtraction operation circuit takes the voltage signal output by the first subtraction operation circuit and the voltage signal output by the voltage follower circuit as inputs, the adjustment of the voltage signal will in turn cause the adjustment of the voltage signal output by the second subtraction operation circuit. On the other hand, the resistance value of the voltage adjustment circuit can also be adjusted through the second control signal, thereby further converting the voltage signal into the voltage signal required by the host computer system. Through the dual adjustment of the first and second control signals, the range of the final output voltage signal can be made larger, thereby meeting the different voltage requirements of the host computer system for sensors with different current ranges. Attached Figure Description

[0016] Figure 1 These are schematic diagrams of the laser system in some embodiments; Figure 2 This is a schematic diagram of the current detection circuit in some embodiments; Figure 3 This is a schematic diagram of the structure of the first subtraction operation circuit in some embodiments; Figure 4 This is a schematic diagram of the voltage follower circuit in some embodiments; Figure 5 This is a schematic diagram of the second subtraction operation circuit in some embodiments; Figure 6 This is a schematic diagram of the voltage regulation circuit in some embodiments. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0018] The current detection circuit 130 provided in this application can be applied to, for example... Figure 1 The application environment shown. Figure 1 A schematic diagram of the structure of a laser system 10 in some embodiments is shown. The laser system 10 includes a cooling device 110, a current-type conductivity sensor 120, a host computer 140, and a current detection circuit 130. The cooling device 110 is connected to the current-type conductivity sensor 120, the current-type conductivity sensor 120 is connected to the current detection circuit 130, and the current detection circuit 130 is connected to the host computer 140.

[0019] In the above application scenarios, even if current-type conductivity sensors 120 with different current ranges are used, the current detection circuit 130 can control the output voltage range within the voltage range adapted by the host computer 140 according to the different input current ranges. This enables it to be compatible with many current-type conductivity sensors 120 with different current ranges, and all of them can achieve high-precision voltage acquisition.

[0020] In some embodiments, such as Figure 2 As shown, a current detection circuit 130 is provided. The structure of the current detection circuit 130 will be described in detail below, and its specific effects in the above application scenarios will be explained in detail.

[0021] Specifically, the current detection circuit 130 may include: a first subtraction operation circuit 210, a voltage follower circuit 220, a second subtraction operation circuit 230, and a voltage regulation circuit 240; The input terminal of the first subtraction circuit 210 is configured to receive a current signal, and the output terminal of the first subtraction circuit 210 is connected to the first input terminal of the second subtraction circuit 230. The input terminal of the voltage follower circuit 220 is configured to receive a first control signal, and the output terminal of the voltage follower circuit 220 is connected to the second input terminal of the second subtraction circuit 230. The output terminal of the voltage follower circuit 220 is connected to the first input terminal of the voltage regulation circuit 240. The second input terminal of the voltage regulation circuit 240 is configured to receive a second control signal, and the output terminal of the voltage regulation circuit 240 is configured to output a voltage signal.

[0022] The aforementioned current detection circuit 130, on the one hand, can flexibly adjust the resistance value of the voltage follower circuit 220 through the input first control signal, thereby making the voltage signal output by the voltage follower circuit 220... The change is due to the voltage signal output by the second subtraction circuit 230 from the first subtraction circuit 210. and the voltage signal output by the voltage follower circuit 220. As input, therefore, voltage signal The adjustment then causes the voltage signal output by the second subtraction circuit 230 to be affected. On the one hand, the voltage can be adjusted; on the other hand, the resistance of the voltage regulation circuit 240 can be adjusted by the second control signal, thereby further adjusting the voltage signal. Converted into the voltage signal required by the host computer 140 system. By adjusting the first and second control signals, the final output voltage signal can be made... The range is wider, thus meeting the different voltage requirements of the host computer 140 system for sensors with different current ranges.

[0023] In some embodiments, reference may be made to Figure 3 As shown, Figure 3 A schematic diagram of the structure of the first subtraction circuit 210 in some embodiments is shown.

[0024] Specifically, the first subtraction circuit 210 may include a first operational amplifier U1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, and a fifth resistor R5; wherein, One end of the first resistor R1 is connected to one end of the second resistor R2 and is configured to connect to the positive terminal IV+ of the current signal. The other end of the second resistor R2 is connected to one end of the fourth resistor R4 and the non-inverting input terminal of the first operational amplifier U1. The other end of the fourth resistor R4 is connected to analog ground AGND. The other end of the first resistor R1 is connected to one end of the third resistor R3 and is configured to connect to the negative terminal IV- of the current signal. The other end of the third resistor R3 is connected to one end of the fifth resistor R5 and the inverting input terminal of the first operational amplifier U1. The other end of the fifth resistor R5 is connected to the output terminal of the first operational amplifier U1.

[0025] In this embodiment, the direction of the input current is from the positive terminal IV+ of the current signal to the negative terminal IV- of the current signal. When the current passes through the first resistor R1, a voltage U is generated across the first resistor R1. i+ U i- In the first subtraction circuit 210, the voltage signal output by the first subtraction circuit 210 is... A voltage U is generated across the first resistor R1. i+ U i- The relationship between them can be expressed by the following formula: ; The relationship between the resistance values ​​of the second resistor R2, the third resistor R3, the fourth resistor R4, and the fifth resistor R5 can be more clearly defined using the above formula. In practical applications, the desired effect can be achieved by adjusting the resistance values ​​of the second resistor R2, the third resistor R3, the fourth resistor R4, and the fifth resistor R5. with U i +、U i Adjustment of the ratio relationship between -

[0026] In some embodiments, the resistance values ​​of the second resistor R2, the third resistor R3, the fourth resistor R4, and the fifth resistor R5 can be set to be the same.

[0027] That is, when R2=R3=R4=R5, the above formula can be simplified to a 1:1:1 relationship, thus making the circuit simpler and easier to control. ; In this embodiment, the first subtraction circuit 210 described above is used to convert the input current signals IV+ and IV- into voltage signals required for subsequent circuits. .

[0028] In some embodiments, reference Figure 4 As shown, the voltage follower circuit 220 may include a second operational amplifier U2, a first digital potentiometer U5, and a sixth resistor R6; wherein, The A terminal of the first digital potentiometer U5 is connected to the analog power supply VCC, the B terminal of the first digital potentiometer U5 is connected to one end of the sixth resistor R6, the AD0 terminal of the first digital potentiometer U5 is connected to digital ground DGND, the W terminal of the first digital potentiometer U5 is connected to the non-inverting input terminal of the second operational amplifier U2, the VDD terminal of the first digital potentiometer U5 is connected to the digital power supply VDD, the GND terminal of the first digital potentiometer U5 is connected to digital ground DGND, and the SCL and SDA terminals of the first digital potentiometer U5 are configured to receive the first control signal transmitted via the I2C bus. The inverting input of the second operational amplifier U2 is connected to the output of the second operational amplifier U2 and the non-inverting input of the second subtraction circuit 230. The other end of the sixth resistor R6 is connected to digital ground DGND.

[0029] In this embodiment, the voltage signal output by the voltage follower circuit 220 The relationship between the second operational amplifier U2, the first digital potentiometer U5, and the sixth resistor R6 in the voltage follower circuit 220 can be expressed by the following formula: ; The voltage follower circuit 220 is used to adjust the input voltage signal according to the instructions transmitted on the I2C bus, such as the first control signal. Converted into the voltage signal required for subsequent circuitry. The voltage signal output by the voltage follower circuit 220 That is, the voltage signal output by the second operational amplifier U2. This is equal to the voltage signal input to the input terminal of the second operational amplifier U2. Voltage signal The adjustment can be achieved through the resistance value. This is achieved through adjustment, and the resistance value... It is the resistance value between the A and W terminals of the first digital potentiometer U5, which can be adjusted by the first control signal connected to the SCL and SDA terminals of the first digital potentiometer U5. The first control signal can be the instruction signal transmitted by the host computer 140 system through the I2C bus. This refers to the resistance between terminals A and B of the first digital potentiometer U5.

[0030] In some embodiments, reference Figure 5 As shown, the second subtraction circuit 230 may include a third operational amplifier U3, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, and a tenth resistor R10. One end of the seventh resistor R7 is connected to the output of the voltage follower circuit 220, and the other end of the seventh resistor R7 is connected to one end of the ninth resistor R9 and the non-inverting input of the third operational amplifier U3. One end of the eighth resistor R8 is connected to the output of the first subtraction circuit 210, and the other end of the eighth resistor R8 is connected to one end of the tenth resistor R10 and the inverting input of the third operational amplifier U3. The other end of the tenth resistor R10 is connected to analog ground AGND, and the other end of the ninth resistor R9 is connected to the output of the third operational amplifier U3.

[0031] In this embodiment, the second subtraction circuit 230 can convert the voltage signal... and Converted into the voltage signal required for subsequent circuitry. Furthermore, the voltage signal output by the second subtraction circuit 230 It can be achieved by connecting the voltage signal of the second subtraction circuit 230. and Adjustments are made, that is, the voltage signal output by the voltage follower circuit 220 is adjusted. and the voltage signal output by the first subtraction circuit 210 Adjustments will be made.

[0032] In some embodiments, the resistance values ​​of the seventh resistor R7, the eighth resistor R8, the ninth resistor R9, and the tenth resistor R10 are the same. In this embodiment, by configuring the seventh resistor R7, the eighth resistor R8, the ninth resistor R9, and the tenth resistor R10 with the same resistance value, that is, when R7=R8=R9=R10, the voltage signal... With voltage signal and The relationship between them can be simplified as follows: .

[0033] In some embodiments, reference Figure 6 As shown, the voltage regulation circuit 240 includes a fourth operational amplifier U4, a second digital potentiometer U6, and a twelfth resistor R12; wherein, Terminal A of the second digital potentiometer U6 is connected to terminal W of the second digital potentiometer U6 and the output terminal of the fourth operational amplifier U4. Terminal B of the second digital potentiometer U6 is connected to the inverting input terminal of the fourth operational amplifier U4 and one end of the twelfth resistor R12. Terminal AD0 of the second digital potentiometer U6 is connected to the digital power supply VDD. Terminal VDD of the second digital potentiometer U6 is connected to the digital power supply VDD. Terminal GND of the second digital potentiometer U6 is connected to digital ground. Terminals SDA and SCL of the second digital potentiometer U6 are configured to receive a second control signal transmitted via the I2C bus. The non-inverting input of the fourth operational amplifier U4 is connected to the output of the second subtraction circuit 230, and the other end of the twelfth resistor R12 is connected to analog ground AGND.

[0034] In this embodiment, the voltage regulation circuit 240 may include a fourth operational amplifier U4, a second digital potentiometer U6, and a twelfth resistor R12. The voltage signal output by the voltage regulation circuit 240... The voltage regulation circuit 240 is connected to the first input terminal. The relationship between the second control signal connected to the second input terminal of the voltage regulation circuit 240 and the second control signal can be seen in the following formula: ; in, This indicates the resistance between terminals B and W of the second digital potentiometer U6. The adjustment can be made by a second control signal connected to the SDA and SCL terminals of the second digital potentiometer U6. The second control signal can be a command signal transmitted by the host computer 140 system via the I2C bus.

[0035] In some embodiments, the current detection circuit 130 further includes an eleventh resistor R11; wherein one end of the eleventh resistor R11 is connected to the output terminal of the second subtraction operation circuit 230, and the other end of the eleventh resistor R11 is connected to the non-inverting input terminal of the fourth operational amplifier U4.

[0036] In this embodiment, by setting an eleventh resistor R11 at the non-inverting input terminal of the fourth operational amplifier U4, the input impedance of the fourth operational amplifier U4 can be increased, thereby further reducing the impact of leakage current on the output stability of the fourth operational amplifier U4.

[0037] In some embodiments, the current detection circuit 130 further includes a host computer 140, which is connected to the input terminal of the voltage follower circuit 220, the second input terminal of the voltage regulation circuit 240, and the output terminal of the voltage regulation circuit 240.

[0038] In this embodiment, the host computer 140 can send a first control signal to the input terminal of the voltage follower circuit 220, such as the port in the first digital potentiometer used to receive control signals. The host computer 140 can also send a second control signal to the second input terminal of the voltage regulation circuit 240, such as the port in the second digital potentiometer U6 used to receive control signals. The host computer 140 can also transmit the converted voltage signal that conforms to the receiving range of the host computer 140 to the host computer 140 for detection.

[0039] Those skilled in the art will understand that Figure 1The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the system to which the present application is applied. A specific laser system may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0040] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0041] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A current detection circuit, characterized in that, The circuit includes: a first subtraction circuit, a voltage follower circuit, a second subtraction circuit, and a voltage regulation circuit; The input terminal of the first subtraction circuit is configured to receive a current signal, and the output terminal of the first subtraction circuit is connected to the first input terminal of the second subtraction circuit. The input terminal of the voltage follower circuit is configured to receive a first control signal, and the output terminal of the voltage follower circuit is connected to the second input terminal of the second subtraction circuit. The output terminal of the voltage follower circuit is connected to the first input terminal of the voltage regulation circuit, the second input terminal of the voltage regulation circuit is configured to receive a second control signal, and the output terminal of the voltage regulation circuit is configured to output a voltage signal.

2. The circuit according to claim 1, characterized in that, The first subtraction circuit includes a first operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, and a fifth resistor; wherein, One end of the first resistor is connected to one end of the second resistor and is configured to be connected to the positive terminal of the current signal. The other end of the second resistor is connected to one end of the fourth resistor and the non-inverting input terminal of the first operational amplifier. The other end of the fourth resistor is connected to analog ground. The other end of the first resistor is connected to one end of the third resistor and is configured to be connected to the negative terminal of the current signal. The other end of the third resistor is connected to one end of the fifth resistor and the inverting input terminal of the first operational amplifier. The other end of the fifth resistor is connected to the output terminal of the first operational amplifier.

3. The circuit according to claim 2, characterized in that, The second resistor, the third resistor, the fourth resistor, and the fifth resistor have the same resistance value.

4. The circuit according to claim 1, characterized in that, The voltage follower circuit includes a second operational amplifier, a first digital potentiometer, and a sixth resistor; wherein... The A terminal of the first digital potentiometer is connected to the analog power supply, the B terminal of the first digital potentiometer is connected to one end of the sixth resistor, the AD0 terminal of the first digital potentiometer is connected to digital ground, the W terminal of the first digital potentiometer is connected to the non-inverting input terminal of the second operational amplifier, the VDD terminal of the first digital potentiometer is connected to the digital power supply, the GND terminal of the first digital potentiometer is connected to digital ground, and the SCL and SDA terminals of the first digital potentiometer are configured to receive the first control signal transmitted via the I2C bus. The inverting input of the second operational amplifier is connected to the output of the second operational amplifier and the non-inverting input of the second subtraction circuit, and the other end of the sixth resistor is connected to digital ground.

5. The circuit according to claim 1, characterized in that, The second subtraction circuit includes a third operational amplifier, a seventh resistor, an eighth resistor, a ninth resistor, and a tenth resistor; One end of the seventh resistor is connected to the output terminal of the voltage follower circuit, and the other end of the seventh resistor is connected to one end of the ninth resistor and the non-inverting input terminal of the third operational amplifier. One end of the eighth resistor is connected to the output terminal of the first subtraction circuit, and the other end of the eighth resistor is connected to one end of the tenth resistor and the inverting input terminal of the third operational amplifier. The other end of the tenth resistor is connected to analog ground, and the other end of the ninth resistor is connected to the output of the third operational amplifier.

6. The circuit according to claim 5, characterized in that, The seventh resistor, the eighth resistor, the ninth resistor, and the tenth resistor have the same resistance value.

7. The circuit according to claim 1, characterized in that, The voltage regulation circuit includes a fourth operational amplifier, a second digital potentiometer, and a twelfth resistor; wherein... The A terminal of the second digital potentiometer is connected to the W terminal of the second digital potentiometer and the output terminal of the fourth operational amplifier. The B terminal of the second digital potentiometer is connected to the inverting input terminal of the fourth operational amplifier and one end of the twelfth resistor. The ADO terminal of the second digital potentiometer is connected to the digital power supply. The VDD terminal of the second digital potentiometer is connected to the digital power supply. The GND terminal of the second digital potentiometer is connected to the digital ground. The SDA and SCL terminals of the second digital potentiometer are configured to receive the second control signal transmitted via the I2C bus. The non-inverting input of the fourth operational amplifier is connected to the output of the second subtraction circuit, and the other end of the twelfth resistor is connected to analog ground.

8. The circuit according to claim 7, characterized in that, The circuit also includes an eleventh resistor; wherein... One end of the eleventh resistor is connected to the output terminal of the second subtraction circuit, and the other end of the eleventh resistor is connected to the non-inverting input terminal of the fourth operational amplifier.

9. The circuit according to claim 1, characterized in that, The current detection circuit also includes a host computer, which is connected to the input terminal of the voltage follower circuit, the second input terminal of the voltage regulation circuit, and the output terminal of the voltage regulation circuit.

10. A laser system, the system comprising a cooling device, a current-type conductivity sensor, a host computer, and a current detection circuit according to any one of claims 1 to 8; wherein, The refrigeration equipment is connected to the current-type conductivity sensor, the current-type conductivity sensor is connected to the current detection circuit, and the current detection circuit is connected to the host computer.

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