CN110554232A - RSSI current detection device for output pin of ROSA - Google Patents
RSSI current detection device for output pin of ROSA Download PDFInfo
- Publication number
- CN110554232A CN110554232A CN201910861889.5A CN201910861889A CN110554232A CN 110554232 A CN110554232 A CN 110554232A CN 201910861889 A CN201910861889 A CN 201910861889A CN 110554232 A CN110554232 A CN 110554232A
- Authority
- CN
- China
- Prior art keywords
- resistance
- multiplexer
- circuit
- mcu
- feedback
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
Abstract
the invention discloses a current detection device of RSSI (received signal strength indicator) for an output pin of a ROSA (receiver-transmitter-receiver), which adopts an I-V (input-voltage) amplification circuit to finish the acquisition of RSSI current, adds a multiplexer on the I-V operational amplification circuit to switch the gear of a feedback resistor so as to expand the input dynamic range, and effectively improves the test precision by compensating the on-resistance of a multiplexer. The current detection device for the RSSI of the output pin of the ROSA can be well used for the current detection technology of the RSSI of the output pin of the ROSA, has the advantages of strong noise resistance and high detection accuracy, and simultaneously meets the requirement of wide-range current measurement.
Description
Technical Field
The present invention relates to a current detection device for RSSI of an output pin of a ROSA.
Background
In the production test process of a ROSA (Receiver Optical Subassembly) product, external equipment is required to be used for carrying out current detection on RSSI (Received Signal Strength Indication) of an output pin of the ROSA, wherein the RSSI output range is 0-1 mA, and the measurement error in a dynamic range (94dB) of 20 nA-1 mA is required to be not more than 2%;
Usually, in order to realize the current measurement with a wide dynamic range, the external device adopts a logarithmic amplifier to nonlinearly amplify the RSSI current and then complete the sampling by the ADC of the MCU, but this method has a high requirement on the test environment, and needs to be connected to the ROSA terminal by an external shielded cable, which has poor noise immunity, and is difficult to control the circuit leakage current, and thus is difficult to satisfy the requirements of production and testing.
Therefore, it is desirable to design a current detection apparatus capable of accurately measuring the RSSI of the output pin of the ROSA.
Disclosure of Invention
The invention aims to overcome the defects that the existing current detection technology for the RSSI of the output pin of the ROSA is poor in noise resistance, not high in detection accuracy and difficult to meet the production test requirement, and provides a novel current detection device for the RSSI of the output pin of the ROSA.
The invention solves the technical problems by adopting the following technical scheme:
The invention provides a current detection device of RSSI (received signal strength indicator) for an output pin of a ROSA (receiver of radio over coax), which is characterized by comprising a relay switch, an I-V (input-output) operational amplifier circuit, a reverse and low-pass filter circuit, a feedback resistor gating control circuit and an MCU (microprogrammed control unit);
the relay switch is connected with an output pin of a ROSA and an input end of the I-V operational amplifier circuit, and is configured to be capable of accessing an RSSI current and gating to form an input current signal and then transmitting the input current signal to the input end of the I-V operational amplifier circuit;
The output end of the I-V operational amplifier circuit is connected to the MCU through the reversing and low-pass filter circuit, and the I-V operational amplifier circuit is configured to convert the input current signal into a voltage signal and amplify the voltage signal, obtain an analog voltage signal through the reversing and low-pass filter circuit and output the analog voltage signal to the MCU;
The feedback resistance gating control circuit is connected between the input end of the I-V operational amplifier circuit and the MCU, is configured to be connected with a negative voltage power supply voltage and a control signal output by the MCU, and is selectively connected to one of the plurality of feedback resistances according to the control signal;
The MCU is configured to be capable of converting the analog voltage signal into a current value through ADC conversion, and to provide the control signal to the feedback resistance gate control circuit.
preferably, the feedback resistance gating control circuit comprises a multiplexer and the plurality of feedback resistances, the plurality of feedback resistances are selectively connected between the multiplexer and the input end of the I-V operational amplifier circuit, the multiplexer is connected to the MCU through an inverting amplification circuit, and the inverting amplification circuit is configured to convert a positive voltage level signal output by the MCU into the control signal of negative voltage and input the control signal of negative voltage into the multiplexer.
Preferably, the relay switch has a pre-stage switch portion and a post-stage connection portion, the post-stage connection portion is connected with the multiplexer, the pre-stage switch portion is configured to be selectively connected to an output pin of the ROSA or a calibration branch, and the calibration branch is connected with a calibration voltage through a calibration resistor;
The multiplexer is provided with a conducting circuit part, two ends of the conducting circuit part are connected with an on-resistance testing device in parallel, and the on-resistance testing device is configured to be capable of measuring voltages at two ends of the conducting circuit part and calculating the on-resistance of the conducting circuit part according to a formula (1);
Ron＝Vout*(Rc+Ri)/Vcc(1)；
in formula (1), Ron represents a resistance value of the on-resistance, Vout represents a voltage value across the on-circuit part, Rc represents a resistance value of the calibration resistance, Ri represents an internal resistance value of the preceding stage switch part and the succeeding stage connection part, and Vcc represents a voltage value of the calibration voltage.
Preferably, the multiplexer is further configured to provide a compensation resistor for the plurality of feedback resistors according to the resistance value of the on-resistor.
preferably, the multiplexer includes a gate switch and a trigger mechanism, the feedback resistor includes a zero-ohm resistor therein, and the pre-stage switch portion of the relay switch is further configured to trigger the gate switch to access the zero-ohm resistor via the trigger mechanism when it is operated to a position connected to the calibration branch.
Preferably, the triggering mechanism includes a trip connection device that can selectively connect the gate switch to the zero-ohm resistor, the trip connection device having a fixed contact portion connected to the gate switch and a movable contact portion configured to be selectively connectable to one of the plurality of feedback resistors;
The trip connection device is configured to be capable of connecting the zero ohm resistor by the movable contact section in response to an operation of connecting the pre-stage switch section to the position of the calibration branch, and disconnecting the zero ohm resistor after connecting the zero ohm resistor for a preset trip connection time threshold.
preferably, the trip connection means is further configured to connect to the one of the plurality of feedback resistors having the largest resistance value immediately after the movable contact portion is disconnected from the zero-ohm resistor.
on the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.
The positive progress effects of the invention are as follows:
The current detection device for the RSSI of the output pin of the ROSA can be well used for the current detection technology of the RSSI of the output pin of the ROSA, has the advantages of strong noise resistance and high detection accuracy, and simultaneously meets the requirement of wide-range current measurement.
Drawings
Fig. 1 is a circuit diagram of a current detection apparatus for RSSI of an output pin of a ROSA according to a preferred embodiment of the present invention.
Fig. 2 is a circuit diagram of a feedback resistor gating control circuit portion in the current detection apparatus for RSSI of an output pin of a ROSA according to the preferred embodiment of the present invention.
Fig. 3 is a schematic diagram of measuring an on-resistance of a multiplexer in the current detection apparatus for RSSI of an output pin of a ROSA according to the preferred embodiment of the present invention.
Detailed Description
The following detailed description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings, is intended to be illustrative, and not restrictive, and any other similar items may be considered within the scope of the present invention.
in the following detailed description, directional terms, such as "left", "right", "upper", "lower", "front", "rear", and the like, are used with reference to the orientation as illustrated in the drawings. The components of various embodiments of the present invention can be positioned in a number of different orientations and the directional terminology is used for purposes of illustration and is in no way limiting.
Referring to fig. 1-2, the current detection apparatus for RSSI of an output pin of a ROSA according to the preferred embodiment of the present invention includes a relay switch, an I-V operational amplifier circuit, an inverting and low-pass filter circuit, a feedback resistance gate control circuit, and an MCU.
The relay switch is connected with an output pin of a ROSA and an input end of the I-V operational amplifier circuit, and is configured to be capable of accessing an RSSI current and gating to form an input current signal and then transmitting the input current signal to the input end of the I-V operational amplifier circuit.
the output end of the I-V operational amplifier circuit is connected to the MCU through the reversing and low-pass filter circuit, and the I-V operational amplifier circuit is configured to convert the input current signal into a voltage signal and amplify the voltage signal, obtain an analog voltage signal through the reversing and low-pass filter circuit and output the analog voltage signal to the MCU.
The feedback resistance gating control circuit is connected between the input end of the I-V operational amplifier circuit and the MCU, is configured to be connected with a negative voltage power supply voltage and a control signal output by the MCU, and is selectively connected to one of the plurality of feedback resistances according to the control signal. The MCU is configured to be capable of converting the analog voltage signal into a current value through ADC conversion, and to provide the control signal to the feedback resistance gate control circuit.
It should be understood that, optionally, the current detection device further includes a necessary driving circuit configured to be able to drive the action of the relay switch via MCU control, and the specific action and action sequence of the relay switch driven by the driving circuit will be exemplified in further detail in the following description of the preferred embodiments. More specifically, the MCU may be preset with a specific control instruction or the like for driving the relay switch.
According to some preferred embodiments of the present invention, the feedback resistor gating control circuit includes a multiplexer and the plurality of feedback resistors, the plurality of feedback resistors are selectively connected between the multiplexer and the input terminal of the I-V operational amplifier circuit, the multiplexer is connected to the MCU via an inverting amplifier circuit, and the inverting amplifier circuit is configured to convert a positive voltage level signal output by the MCU into the control signal of a negative voltage and input the control signal of a negative voltage to the multiplexer.
As shown in fig. 1, the ROSA detection current is output to the test board through the RSSI, and is gated by the relay switch to be input to the I-V amplification circuit to convert the RSSI current signal into a voltage signal and amplify the voltage signal, and then the voltage signal is sent to the MCU pin through the post-stage reverse and active low-pass filter circuit to be converted by the ADC to obtain the RSSI current value. In addition, in the I-V amplifying circuit, a multiplexer is used for switching a gear mode, so that the measurement of the input current with a wide dynamic range is realized. The MCU controls the multiplexer to select different feedback resistors, so that the current monitoring capability in a wide dynamic range can be realized.
Generally, a mode of switching gears of a relay adopted for realizing a wider input dynamic measurement range is not suitable for application in a production test environment because the switching speed of the relay is slower and the occupied space is larger. Compared with the prior art, the embodiment of the invention has the advantages that the RSSI current monitoring in a wide dynamic range is realized by adopting a mode of rapidly switching different feedback resistors by the multiplexer, and the method has obvious advantages.
According to some application examples of the invention, the multiplexer can be powered by connecting the GND pin of the multiplexer to the 2.5V power plane of the test board and connecting the VCC power pin of the multiplexer to the GND plane of the test board, so that distortion-free transmission of the I-V output negative voltage signal (relative to the GND plane) can be realized. Optionally, the multiplexer is powered by a negative voltage power supply mode (relative to the plane of the test board GND), and the control signal is also controlled by a negative voltage, specifically, a reverse amplification circuit can be used to convert a 0-3.3V control signal output by the MCU into a-2.5V-0V control signal.
According to some preferred embodiments of the present invention, the relay switch has a preceding stage switch portion and a succeeding stage connection portion, the succeeding stage connection portion being connected to the multiplexer, the preceding stage switch portion being configured to be selectively connectable to an output pin of the ROSA or a calibration branch, the calibration branch being connected to a calibration voltage via a calibration resistor;
the multiplexer is provided with a conducting circuit part, two ends of the conducting circuit part are connected with an on-resistance testing device in parallel, and the on-resistance testing device is configured to be capable of measuring voltages at two ends of the conducting circuit part and calculating the on-resistance of the conducting circuit part according to a formula (1);
Ron＝Vout*(Rc+Ri)/Vcc(1)；
in formula (1), Ron represents a resistance value of the on-resistance, Vout represents a voltage value across the on-circuit part, Rc represents a resistance value of the calibration resistance, Ri represents an internal resistance value of the preceding stage switch part and the succeeding stage connection part, and Vcc represents a voltage value of the calibration voltage.
further preferably, the multiplexer is further configured to provide a compensation resistor to the plurality of feedback resistors according to the resistance value of the on-resistor.
According to some preferred embodiments of the present invention, the triggering mechanism includes a trip connection device that can selectively connect the gate switch to the zero-ohm resistor, the trip connection device having a fixed contact portion and a movable contact portion, the fixed contact portion being connected to the gate switch, the movable contact portion being configured to be selectively connectable to one of the plurality of feedback resistors;
the trip connection device is configured to be capable of connecting the zero ohm resistor by the movable contact section in response to an operation of connecting the pre-stage switch section to the position of the calibration branch, and disconnecting the zero ohm resistor after connecting the zero ohm resistor for a preset trip connection time threshold.
Therefore, the method can help automatically ensure that before the current detection of the RSSI of the output pin of the ROSA each time, the accurate compensation resistor is conveniently and automatically calculated, no additional operation is needed, and the problem that the current detection of the RSSI is not accurate enough is solved. In addition, the tripping connection device with the fixed contact part and the movable contact part can be realized by an electromagnetic tripping switch device with a simple structure and small occupied space.
according to some further preferred embodiments of the present invention, the trip connection means is further configured to connect to the one of the plurality of feedback resistors having the largest resistance value immediately after the movable contact part is disconnected from the zero-ohm resistor. Thus, the current detection operation of the RSSI can be further simplified.
Specifically, the multiplexer may be a 74HC4851 model multiplexer.
The following description is made in connection with an application example of the above preferred embodiment according to the present invention. As shown in fig. 3, after the test board is powered on, the relay switch at the previous stage of the I-V op-amp circuit may be first powered on to conduct the NO contact and the COM terminal, and then enter the Ron calibration mode, and the Rc resistor is pulled up to the Vcc power supply to provide the standard current of 20mA (for example, Vcc is 5V, and Rc is 0.25K ohm), and the relay switch selects the low-on internal resistance relay, and sets the feedback resistor to R1 is 0 ohm.
The resistance value for Ron can be calculated using equation (1) above. In the case that the internal resistance of the relay switch is negligible, equation (1) can be simplified as follows: ron is Vout Rc/Vcc. After the measurement work of the on-resistance is completed through the process, the relay switch is turned off to enable the NC contact and the COM end to be conducted to enter an RSSI current measurement mode, and the Ron measurement result is compensated to the feedback resistance, so that the influence of the on-resistance Ron on the measurement precision can be reduced or even eliminated.
In addition, according to some application examples of the present invention, the positive voltage supply pin of the I-V op-amp may be connected to +2.5V, the negative voltage supply pin may be connected to-2.5V, and the feedback resistors R1-R8 satisfy R8> R7> R6> R5> R4> R3> R2> R1, and by default, the selection of conduction from the feedback resistor R8 path is allowed, when the ADC voltage is detected to exceed a set value (e.g., 2.4V), the feedback resistor path is switched to R7, if the ADC voltage still exceeds 2.4V, the feedback resistor path is switched to R6, and so on, when the voltage is detected to be less than 2.4V, the appropriate gear is achieved.
while specific embodiments of the invention have been described above, it will be appreciated by those skilled in the art that these are by way of example only, and that the scope of the invention is defined by the appended claims. Various changes and modifications to these embodiments may be made by those skilled in the art without departing from the spirit and scope of the invention, and these changes and modifications are within the scope of the invention.
Claims (8)
1. A current detection device for RSSI of an output pin of a ROSA is characterized in that the current detection device comprises a relay switch, an I-V operational amplifier circuit, a reverse and low-pass filter circuit, a feedback resistance gating control circuit and an MCU;
The relay switch is connected with an output pin of a ROSA and an input end of the I-V operational amplifier circuit, and is configured to be capable of accessing an RSSI current and gating to form an input current signal and then transmitting the input current signal to the input end of the I-V operational amplifier circuit;
The output end of the I-V operational amplifier circuit is connected to the MCU through the reversing and low-pass filter circuit, and the I-V operational amplifier circuit is configured to convert the input current signal into a voltage signal and amplify the voltage signal, obtain an analog voltage signal through the reversing and low-pass filter circuit and output the analog voltage signal to the MCU;
The feedback resistance gating control circuit is connected between the input end of the I-V operational amplifier circuit and the MCU, is configured to be connected with a negative voltage power supply voltage and a control signal output by the MCU, and is selectively connected to one of the plurality of feedback resistances according to the control signal;
The MCU is configured to be capable of converting the analog voltage signal into a current value through ADC conversion, and to provide the control signal to the feedback resistance gate control circuit.
2. The current sensing device of claim 1, wherein the feedback resistor gating control circuit comprises a multiplexer and the plurality of feedback resistors, the plurality of feedback resistors being selectively connected between the multiplexer and the input terminal of the I-V op-amp circuit, the multiplexer being connected to the MCU via an inverting amplifier circuit, the inverting amplifier circuit being configured to convert a positive voltage level signal output by the MCU into the control signal of negative voltage and to input the control signal of negative voltage to the multiplexer.
3. The current detection device according to claim 2, wherein the relay switch has a preceding stage switch section and a succeeding stage connection section, the succeeding stage connection section being connected to the multiplexer, the preceding stage switch section being configured to be selectively connectable to an output pin of the ROSA or a calibration branch, the calibration branch being connected to a calibration voltage via a calibration resistor;
The multiplexer is provided with a conducting circuit part, two ends of the conducting circuit part are connected with an on-resistance testing device in parallel, and the on-resistance testing device is configured to be capable of measuring voltages at two ends of the conducting circuit part and calculating the on-resistance of the conducting circuit part according to a formula (1);
Ron＝Vout*(Rc+Ri)/Vcc (1)；
In formula (1), Ron represents a resistance value of the on-resistance, Vout represents a voltage value across the on-circuit part, Rc represents a resistance value of the calibration resistance, Ri represents an internal resistance value of the preceding stage switch part and the succeeding stage connection part, and Vcc represents a voltage value of the calibration voltage.
4. the current sensing device of claim 3, wherein the multiplexer is further configured to provide a compensation resistance to the plurality of feedback resistors based on the resistance of the on-resistance.
5. The current sensing device of claim 3, wherein the multiplexer includes a gate switch and a trigger mechanism, the feedback resistor including a zero ohm resistor therein, the pre-stage switching portion of the relay switch further configured to trigger the gate switch to access the zero ohm resistor via the trigger mechanism when operated to a position connected to the calibration branch.
6. The current sensing device of claim 5, wherein the trigger mechanism includes a trip connection that selectively couples the gate switch into the zero ohm resistor, the trip connection having a fixed contact portion coupled to the gate switch and a movable contact portion configured to be selectively coupled to one of the plurality of feedback resistors;
the trip connection device is configured to be capable of connecting the zero ohm resistor by the movable contact section in response to an operation of connecting the pre-stage switch section to the position of the calibration branch, and disconnecting the zero ohm resistor after connecting the zero ohm resistor for a preset trip connection time threshold.
7. The current sensing device of claim 6, wherein the trip connection means is further configured to enable connection to a largest one of the plurality of feedback resistors immediately after the movable contact portion is disconnected from the zero ohm resistor.
8. The current sensing device of claim 2, wherein the multiplexer is a 74HC4851 model multiplexer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910861889.5A CN110554232A (en) | 2019-09-12 | 2019-09-12 | RSSI current detection device for output pin of ROSA |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910861889.5A CN110554232A (en) | 2019-09-12 | 2019-09-12 | RSSI current detection device for output pin of ROSA |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN110554232A true CN110554232A (en) | 2019-12-10 |
Family
ID=68739978
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201910861889.5A Withdrawn CN110554232A (en) | 2019-09-12 | 2019-09-12 | RSSI current detection device for output pin of ROSA |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN110554232A (en) |
Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4041845A1 (en) * | 1990-12-24 | 1992-06-25 | Halbleiterwerk Frankfurt Gmbh | Measuring circuitry for low currents esp. for automatic test system - has operational amplifier supplying analogue multiplexer connected to measuring input directly at inverting input and via relay at non-inverting input |
| CN101036324A (en) * | 2004-09-30 | 2007-09-12 | 英特尔公司 | Mechanism to select bandwidth in an optical receiver circuit |
| CN203365537U (en) * | 2013-07-15 | 2013-12-25 | 长城电器集团有限公司 | Autoreclose circuit breaker leakage current detection circuit |
| CN203554442U (en) * | 2013-10-22 | 2014-04-16 | 青岛海信宽带多媒体技术有限公司 | RSSI monitoring circuit |
| CN104300502A (en) * | 2014-09-26 | 2015-01-21 | 哈尔滨威帝电子股份有限公司 | Intelligent vehicle-mounted power device with current direction and short-circuit protection functions |
| CN106707213A (en) * | 2016-12-29 | 2017-05-24 | 武汉数字工程研究所（中国船舶重工集团公司第七0九研究所） | Digital integrated circuit standard sample chip |
| CN208334487U (en) * | 2018-07-19 | 2019-01-04 | 重庆力华科技有限责任公司 | A kind of vehicle power supply voltage falls detection circuit |
| CN109342805A (en) * | 2018-11-21 | 2019-02-15 | 陕西电器研究所 | A kind of high-precision micro-ampere current detection circuit |
-
2019
- 2019-09-12 CN CN201910861889.5A patent/CN110554232A/en not_active Withdrawn
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4041845A1 (en) * | 1990-12-24 | 1992-06-25 | Halbleiterwerk Frankfurt Gmbh | Measuring circuitry for low currents esp. for automatic test system - has operational amplifier supplying analogue multiplexer connected to measuring input directly at inverting input and via relay at non-inverting input |
| CN101036324A (en) * | 2004-09-30 | 2007-09-12 | 英特尔公司 | Mechanism to select bandwidth in an optical receiver circuit |
| CN203365537U (en) * | 2013-07-15 | 2013-12-25 | 长城电器集团有限公司 | Autoreclose circuit breaker leakage current detection circuit |
| CN203554442U (en) * | 2013-10-22 | 2014-04-16 | 青岛海信宽带多媒体技术有限公司 | RSSI monitoring circuit |
| CN104300502A (en) * | 2014-09-26 | 2015-01-21 | 哈尔滨威帝电子股份有限公司 | Intelligent vehicle-mounted power device with current direction and short-circuit protection functions |
| CN106707213A (en) * | 2016-12-29 | 2017-05-24 | 武汉数字工程研究所（中国船舶重工集团公司第七0九研究所） | Digital integrated circuit standard sample chip |
| CN208334487U (en) * | 2018-07-19 | 2019-01-04 | 重庆力华科技有限责任公司 | A kind of vehicle power supply voltage falls detection circuit |
| CN109342805A (en) * | 2018-11-21 | 2019-02-15 | 陕西电器研究所 | A kind of high-precision micro-ampere current detection circuit |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN108172152B (en) | Current detection device and detection method of display panel | |
| US20130027015A1 (en) | Multi input circuit | |
| CN112198419A (en) | Automatic test system for PCB | |
| CN111880052A (en) | Hand-held type partial discharge detection device based on bluetooth interconnection terminal cluster | |
| CN110554232A (en) | RSSI current detection device for output pin of ROSA | |
| US8786296B2 (en) | Resistance-measuring circuit and electronic device using the same | |
| CN206818800U (en) | A kind of resistance measuring instrument | |
| CN102004686B (en) | Current measuring device and computer system thereof | |
| CN218767097U (en) | Current detection device and electrical equipment | |
| CN210514461U (en) | Hand-held transformer direct-current resistance tester | |
| CN111123073B (en) | Quick self-checking device of hardware board card | |
| CN113504447A (en) | Semiconductor device parameter testing device | |
| CN202502157U (en) | Apparatus for measuring resistance-type parameter and equipment voltage | |
| CN107015177B (en) | Automatic range switching circuit of declination inclinometer | |
| CN113985109B (en) | Weak current measurement device and system | |
| CN117330805B (en) | Automatic gear shifting circuit for current detection and current detection device | |
| CN113064524A (en) | Touch detection system and method and display module | |
| CN112269340A (en) | Multi-signal type high-precision acquisition card | |
| CN106093822B (en) | Automatic zero calibration circuit for differential voltage probe | |
| CN217954556U (en) | Low current measurement module for eliminating bias voltage error through commutation | |
| CN112180173A (en) | Measuring device | |
| CN111903211B (en) | Remote temperature measuring device | |
| JPS59212997A (en) | Multipoint input switch | |
| CN210922683U (en) | Batch detection circuit based on temperature and humidity sensor, PCB and device thereof | |
| CN114460875B (en) | Power supply circuit and camera testing device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| WW01 | Invention patent application withdrawn after publication |
Application publication date: 20191210 |
|
| WW01 | Invention patent application withdrawn after publication |