CN109767887B - Method for combining given output resistance values in series-parallel connection - Google Patents

Abstract

The invention discloses a method for combining a given output resistance value in series and parallel, and aims to provide a method for quickly setting, high precision, and accurately combining a given output resistance value in series and parallel. The present invention is realized through the following technical solution: with an interval value of 100Ω, four 200Ω and one 100Ω resistor units are used, and are connected in series to form a hundred-digit resistor combination with an arithmetic sequence resistance value of 0Ω to 900Ω that is connected to the circuit. ; Use the interval value as 10Ω and connect in series as above to form a ten-digit resistor combination with a circuit range of 0Ω ~ 90Ω; use an interval value of 1Ω and follow the above method to form a single-digit resistor combination with an access circuit range of 0Ω ~ 9Ω. body; with an interval value of 0.1Ω, form a tenth resistor combination with a range of 0Ω to 0.9Ω connected to the circuit in the above manner; thus the maximum value is 900+90+9+0.9=999.9Ω, and the minimum resolution is A resistance of 0.1Ω is given.

Description

Method of series and parallel combination of given output resistance values

Technical field

The present invention is mainly used to provide a method for providing a series-parallel combination of a given output resistance value in a testing environment for resistance signals.

Background technique

Resistors, capacitors and inductors are the most commonly used devices and types in electronic circuits. Resistors are divided into fixed resistors and variable resistors. An adjustable resistor is a kind of resistor, which can play the role of a resistor in electronic circuits. It is different from ordinary resistors in that its resistance value can continuously change within a certain range. In some applications that require the resistance value to change infrequently, In case of changes, an adjustable resistor can be used. Due to the structure and use of adjustable resistors, the failure rate is significantly higher than that of ordinary resistors. There are many types of adjustable resistors with different structures and different definitions. For wire-wound adjustable resistors, the resistor wire is wound around a frame to make a circular or spiral-shaped resistor. For thin-film or thick-film adjustable resistors, a resistive film is formed on a common substrate. The shape is mostly horseshoe-shaped or round. Arc or long strip. For synthetic solid core adjustable resistors, a horseshoe-shaped or long strip-shaped resistor rail is compression molded on the base. The resistor body of the contact-type adjustable resistor, on which the movable contact contacts and slides, slides along the resistor body, and draws out the input voltage, is called a brush or a contact-type inlet brush. A variable resistor is an electromechanical component that relies on a slider to slide on a resistor body to change the resistance of the resistor. Variable resistors can be divided into rheostats and potentiometers according to their uses. Rheostats are often called adjustable resistors. Their characteristic is that the resistance value can be changed by changing the position of the slider. The potentiometer is a voltage dividing device that relies on the slider to slide on the resistor to obtain an output voltage that is related to the displacement of the slider. A potentiometer can also be used as a rheostat by connecting the center tap to either of the other two legs to create a rheostat. The resistor must be measured when in use to see if its resistance matches the nominal value. A potentiometer is actually a variable resistor and can be made from any of the materials mentioned above. Potentiometers usually consist of two fixed outputs and a sliding tap. According to the structure, potentiometers can be divided into single-turn, multi-turn; single-link, double-link; with switch; locking and non-locking potentiometers. According to the adjustment method, it can be divided into rotary potentiometer and straight sliding potentiometer. In the rotary potentiometer, according to the relationship between the resistance value and the rotation angle of the potentiometer, it can be divided into linear type, exponential type, and logarithmic type. When the variable resistor changes the resistance value, due to improper distribution of the adjustable resistor resistance, improper coordination of the rotation system, and the existence of contact resistance in the adjustable resistor, the output end will not have useful signals except when the moving contact moves on the surface of the resistor body. , is also accompanied by contact noise, resolution noise and short-circuit noise that fluctuate with the signal. Resolution noise is caused by the stepwise change of resistance, while short-circuit noise is caused when the moving contact moves on the winding. Occurs when adjacent turns are shorted. For wirewound adjustable resistors and linear adjustable resistors, the resolution is expressed as the percentage of the change in resistance caused by the moving contact moving one turn on the winding to the total resistance. For adjustable resistors with functional characteristics, resolution is a variable because the resistance of each turn of the winding is different. At this time, the resolution of the adjustable resistor refers to the average resolution of the section with the largest slope on the function characteristic curve. Commonly used variable resistors include sliding rheostat, resistance box, etc. The sliding rheostat is a variable resistor composed of a resistor and a rotating or sliding system for voltage division. Usually, the resistance wire is wound into a coil, and the length of the resistance wire connected to the circuit is changed by sliding the slider, thereby changing the resistance value. The sliding rheostat can change the resistance connected to the circuit and play the role of continuously changing the current, but it cannot accurately know the resistance value connected to the circuit. If you need to know the resistance of a resistor connected to a circuit, you will use a resistor box. The resistance box is a combination of several fixed-value precision resistors, which are installed in the same box. The box-type resistor changes its resistance value through a conversion device. It is a rheostat that can adjust the resistance size and display the resistance value. This device usually adopts a decade-disc (knob-type) structure, and can also adopt a plug-type and end-button structure as needed. It is compared with the sliding rheostat. The sliding rheostat cannot express the resistance value connected to the circuit, but it can continuously change the resistance connected to the circuit. The resistance box can indicate the resistance value connected to the circuit, but the resistance change is discontinuous and not as accurate as the value change of the sliding rheostat.

In sensor manufacturing and application, changes in measured non-electric quantities (such as displacement, force, acceleration, torque, pressure, etc.) are converted into resistive sensors that change resistance, capacitive sensors that change capacitance, and inductive sensors that change inductance. The idea is to convert the physical quantities that need to be collected into corresponding resistance, capacitance and inductance, and the outputs are corresponding changes in resistance value, capacitance value and inductance value respectively. The required resistance value of the analog resistance signal of the resistive sensor is generally 0~999.9Ω, and the resolution is 0.1Ω. In its system joint test, such as the joint test of a resistive sensor and the system, the corresponding resistor can be used to simulate the change of the resistive sensor. At the same time, the change of the resistor or resistance value is known at the time of setting, and can Analog resistive sensor sets the resistance value of any resistance within the range.

Contents of the invention

The object of the present invention is to provide a method for setting a series-parallel combination of a given output resistance value that is easy to implement, low in cost, fast, high-precision and accurate.

The present invention is achieved through the following measures: a method of combining a given output resistance value in series and parallel, which has the following technical characteristics: at least four 200Ω and one 100Ω resistance units are used at an interval of 100Ω to form an access circuit in series A hundred-digit resistor combination with an arithmetic series resistance ranging from 0Ω to 900Ω; with an interval of 10Ω, at least four 20Ω and one 10Ω resistor units are connected in series to form an access circuit with an arithmetic range of 0Ω to 90Ω. A tens-digit resistor combination with a numerical resistance value; with an interval of 1Ω, at least four 2Ω and 1 resistor units are connected in series to form a single-digit resistor combination with an arithmetic serial resistance value that is connected to the circuit with a range of 0Ω to 9Ω; The interval value is 0.1Ω, and at least four 0.2Ω and one 0.1Ω resistor units are connected in series to form a tenth resistor combination with an arithmetic sequence resistance of 0Ω to 0.9Ω connected to the circuit; thus forming the hundreds and tens digits. , the maximum value of the combination of units and tenths resistance is added, the maximum value is 900+90+9+0.9=999.9Ω, and the minimum resolution is 0.1Ω resistance given device, and each two adjacent series resistors There are double-pole double-connected switches connected in parallel on the series lines at intervals to switch on the relay, so as to realize the short-circuit parallel resistance R contact closure and the contact resistance is reduced by half, corresponding to the selected output of 1 to 9, each time the resistance value is output by The variable resistor microcontroller system counts the number of relay short contacts on the resistance output loop, and the combined output resistance value will be subtracted from the cumulative total resistance value of the relay closed contacts.

Compared with the prior art, the present invention has the following beneficial effects.

Simple to implement. The invention uses a series structure of a hundred-digit series resistor group, a tens-digit series resistor group, a units-digit series resistor group, and a ten-digit series resistor group to form an output resistor, and uses the separation method of hundreds, tens, units, and ten-digits for combination. The required resistance is achieved through the series combination of resistors, the relay contacts are used to short-circuit the excess resistance to achieve the target resistance, and the relay contact contact resistance at the short-circuited resistor is halved through the parallel connection of the relay double poles. At each position of the series resistor group, To obtain the target resistance value, each group can obtain any resistance value from 0 to 999.99Ω with fewer series-connected resistor groups, which is simple to implement. A lot of resources can be saved under the same accuracy conditions. At the same time, the resistance value can be adjusted intelligently through an external digital control device. The resistance value adjustment is more efficient and can avoid damaging the circuit.

low cost. The present invention uses a combination of resistors to complete the variable resistor, which has advantages in high precision and low cost. The resistors with the above resistance value deviations are all off-the-shelf products and do not need to be customized separately. You only need to use the off-shelf resistor XJ3 type precision wire-wound resistor provided by the resistor manufacturer. Installation and adjustment are simple and convenient. Each series resistor group is installed alternately according to positive deviation and negative deviation, which can obtain better accurate value output. Only simple secondary selection is required, and the workload is small.

Given promptly. When the present invention outputs any resistance value from 0 to 999.99Ω, the relay contacts in the hundreds, tens, units and tenths digits are short-circuited according to the combination needs to achieve the output of the target resistance. Each resistance unit combination corresponds to 1 to 9. The selected outputs each have corresponding closed combinations of fixed relay contacts. Each output of the resistance value can count how many relays are in the closed state on the resistance output circuit. The final resistance combination output resistance value minus the relay closed contacts The cumulative total resistance value is easy to implement, responds quickly, has good resistance stability, small resistance temperature coefficient and static noise. It is controlled by a single-chip microcomputer, which is connected to the upper computer through the serial RS485 bus. The upper computer gives the target resistance value, and the resistance output reaches stability within 0.3s. Each resistor combination is positive and negative matched. Install alternately according to the positive and negative deviations of the resistance value to obtain a better accurate resistance value output. Its full-scale precision and accuracy are still considered to be ±0.025%, and the full-scale precision and accuracy are still better than 0.25Ω. This requires secondary screening and matching, and the workload is relatively small.

High precision. The present invention achieves the required resistance through the series combination of resistors. The maximum value of each series-connected resistor group is added to form a maximum value of 999.9Ω, and the minimum resolution is 0.1Ω to form a resistance given device. Multiple combinations are used in different combinations. The resistor is connected in parallel to improve accuracy; and each group of four series resistors is connected in parallel with a relay using double poles on the series line. The double poles of the relay are connected in parallel to reduce the contact resistance of the relay contact at the short-circuited resistor R by half. Each resistor unit corresponds to the closing of a fixed relay contact, and corresponds to the selected output of 1 to 9 to reduce the contact resistance. This series-parallel switching circuit uses a double-pole relay contact connected across the resistor. It can halve the contact resistance of the relay contact at the short-circuit resistance, and the resistance at the short-circuit resistance is ≤0.015Ω. It is very flexible and can improve the output accuracy of the full-scale resistance value with high accuracy. In the range of 0~999.9Ω, the resolution is 0.1Ω. If the combination of hundreds and tens digits obtains a resistance value output of 990Ω, the relay will be fully disconnected. The resistance deviation at this time is the maximum deviation of the combination of hundreds and tens. That is, 10×(±0.002%)=±0.02%. Based on the above, when a resistance value output of 999.9Ω is obtained, the maximum resistance deviation at this time is: 990×(±0.02%)+(±0.02Ω)=(±0.198)+(±0.02)=±0.218Ω. The resistance value range is 0~999.9Ω, the resolution is 0.1Ω, and its full-scale precision and accuracy are better than 0.25Ω, that is, the full-scale precision and accuracy are ±0.025%. Each resistor unit in the hundreds and tens digits of the series resistor group is connected in parallel with 5 resistors of the same specifications and resistance deviation. The resistance deviation of each resistor is ±0.01%, then the resistance value of each resistor unit The maximum deviation is reduced to ±0.01%/5=±0.002%; under the control of an external digital control device, the output resistance value is corrected according to the number of short contacts, so that the resistance of the basic unit of the resistor can be zero or fixed. The resistance value, and when the resistance value of the resistance unit is a fixed resistance value, the fixed resistance value of the resistance unit is different, and the positive and negative matching of the resistor arrangement improves the accuracy and achieves low cost and high accuracy. In this way, in the electronic circuit of intelligent equipment, 2N arbitrary resistance values within a certain range can be conveniently provided through an external digital control device, which facilitates digital control of resistor values in circuit board group applications and facilitates the use of variable resistors when variable resistors are required. Automation is achieved in applications, and at the same time, high-precision adjustable resistors can be designed.

The output of the variable resistor is accurate. The present invention can correct the given resistance value by calculating the number of relay short contacts and using the software of the microcontroller to look up the table corresponding to the number of relay contacts. When this device outputs any resistance value from 0 to 999.99Ω, the relay contacts in the hundreds, tens, ones, and tenths digits are short-circuited according to the combination needs to achieve the output of the target resistance. Each resistance unit combination corresponds to 1 The selection outputs of ~9 each have corresponding closed combinations of fixed relay contacts. Each output of the resistance value can count how many relays are in the closed state on the resistance output loop. The final combined output resistance value of the resistance will be minus the relay. The cumulative total resistance value of the closed contacts, which can further reduce the short-circuit contact resistance. In addition, the relay contact contact resistance at the short-circuit resistor is halved by connecting the relay double poles in parallel. In each bit of the resistor combination, in order to obtain the target resistance value, which is less than or equal to a certain power of the corresponding bit of 9 times 10, a relay contact needs to be used to short-circuit the excess resistance value. Use relay contacts to short-circuit excess resistance to achieve the target resistance, such as a single-digit resistance combination. Use a relay contact short-circuit combination of one-digit resistance combinations to achieve 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9. Select output. At the same time, the resistance at the short-circuit point of the segment is optimized. By using two sets of relay contacts in parallel, the contact resistance is halved. The maximum resistance value of a single contact of the relay is 0.03Ω. After using two sets of relay contacts in parallel, the resistance at the short-circuit point is ≤0.015Ω, which can reduce the short-circuit contact resistance to improve the output accuracy of the final resistance value.

The resistance units R1~R5 of the hundreds-digit series resistor group are installed alternately according to the positive and negative deviations of the resistance values to obtain a more accurate resistance value output; the tens-digit series resistor group R6~R10 and the units-digit series resistor group R11~ R15, tenth place series resistor group R16~R20, each resistance unit is installed alternately with the positive and negative deviation of the resistance value of the R1~R5 resistance unit to obtain a better accurate resistance value output.

Each resistor combination has a positive and negative resistor arrangement, and is installed alternately according to the positive and negative deviations of the resistance value to obtain a more accurate resistance value output. Its full-scale precision and accuracy are still considered to be ±0.025%, and the full-scale accuracy and Accuracy better than 0.25Ω remains unchanged. In this way, the actual accuracy of the resistance value on the entire line has been improved, which requires secondary screening and matching, and the workload is relatively small. Furthermore, the accuracy of the resistor can be improved by connecting multiple resistors in parallel. The given resistance is a combination of resistors in the hundreds, tens, ones and tenths places. Each resistance unit in the ones and tenths places of the resistance combination is made up of 5 resistors of the same specification and resistance value deviation, which are connected in parallel. The resistance value deviation of each resistor is ±0.01Ω, then the maximum deviation of the resistance value of each resistor unit is reduced to ±0.01Ω/5 = ±0.002Ω; if the combination of units and tenths digits obtains a resistance value output of 9.9Ω, the relay Fully disconnected, the resistance deviation at this time is the maximum deviation of the units and tenths combination, that is, 10 × (±0.002Ω) = ± 0.02Ω. Each resistor unit in the hundreds and tens digits of the resistor combination is connected in parallel with 5 resistors of the same specifications and resistance deviation. The resistance deviation of each resistor is ±0.01%, then the resistance value of each resistor unit is the maximum The deviation is reduced to ±0.01%/5=±0.002%; if the combination of hundreds and tens digits obtains a resistance value output of 990Ω, the relay is fully disconnected, and the resistance deviation at this time is the maximum deviation of the combination of hundreds and tens. That is, 10×(±0.002%)=±0.02%. Based on the above, when a resistance value output of 999.9Ω is obtained, the maximum resistance deviation at this time is: 990×(±0.02%)+(±0.02Ω)=(±0.198)+(±0.02)=±0.218Ω. The resistance value range is 0~999.9Ω, the resolution is 0.1Ω, and its full-scale precision and accuracy are better than 0.25Ω, that is, the full-scale precision and accuracy are ±0.025%. This allows for higher priced resistors to be obtained with lower cost resistors.

Strong anti-interference ability. The data transmission of the present invention adopts RS485 to communicate with the host computer. One asynchronous, full-duplex serial port of the microcontroller is electrically connected to the RS485 bus of the host computer. The host computer addresses the resistor given device through the RS485 bus, and the required power is achieved through the series combination of resistors, which has strong anti-interference ability. The required resistance value of the analog resistance signal of the resistive sensor is generally 0 to 999.9Ω, and the resolution is 0.1Ω. Its full-scale precision and accuracy are better than 0.25Ω, that is, the full-scale precision and accuracy are ±0.025%.

Description of the drawings

Figure 1 is a schematic diagram of the circuit principle of resistor combination in the method of series-parallel combination of a given output resistance value according to the present invention.

FIG. 2 is a circuit schematic diagram of an optional embodiment of the typical correspondence between resistance values in FIG. 1.

Figure 3 is the microcontroller communication, control and drive circuit diagram of the resistor card.

Figure 4 is a schematic diagram of the circuit principle of the variable resistor microcontroller system.

Figure 5 is a schematic diagram of a hundred-digit resistor combination forming an arithmetic resistance sequence with a difference of 100Ω and a range of 0Ω to 900Ω.

The present invention will be further described below with reference to the accompanying drawings and examples, but the present invention is not limited to the scope of the described embodiments.

Detailed ways

See Figure 1. According to the present invention, at least four 200Ω and one 100Ω resistor units are used at an interval of 100Ω, and are connected in series to form a hundred-digit resistor combination with an arithmetic sequence resistance of 0Ω to 900Ω in the range of the access circuit; with the interval value being 10Ω, at least 4 20Ω and 1 10Ω resistor units, connected in series to form a ten-digit resistor combination with an arithmetic sequence resistance value of 0Ω to 90Ω in the circuit range; with an interval value of 1Ω, at least 4 2Ω and 1 The resistor units are connected in series to form a single-digit resistor combination with an arithmetic resistance series with an access circuit range of 0Ω to 9Ω; with an interval value of 0.1Ω, at least four 0.2Ω and one 0.1Ω resistor units are connected in series to form an access circuit. The circuit range is a tenth place resistor combination with an arithmetic sequence resistance of 0Ω to 0.9Ω; thus forming the maximum value of the hundreds, tens, units and tenth place resistor combinations, the maximum value is 900+90+9+0.9 =999.9Ω, and the minimum resolution is 0.1Ω resistance given device, and between each two adjacent series resistors, there is a double-pole double switch connected in parallel at intervals on the series line to switch on the relay to achieve short circuit The contact resistance of the parallel resistor R is reduced by half when the contact is closed, corresponding to the selected output of 1 to 9. Each time the resistance value is output, the variable resistor microcontroller system counts the number of relay short contacts on the resistance output loop, and the combined output resistance value will be reduced. Get the cumulative total resistance value of the relay closed contacts. The series structure of the hundreds-digit series resistor group, tens-digit series resistor group, units-digit series resistor group, and ten-digit series resistor group forms the output resistance. The hundreds-digit series resistor group is composed of four 200Ω and one 100Ω R1 ~ R5 resistor units in series to form a series resistor group of 0Ω ~ 900Ω (the interval value is 100Ω) to form the basic structure of the resistance value output of the resistor card; the tens-digit series resistor The group is composed of four 20Ω and one 10Ω R6~R10 resistor units connected in series to form a 0Ω~90Ω (interval value is 10Ω) R11~R15 series resistor group to form the basic structure of the resistance value output of the resistor card; the units group series resistor is The basic structure of the resistance value output of the resistor card is composed of four 2Ω and one 1Ω resistance units connected in series to form a series resistance group of 0Ω to 9Ω (the interval value is 1Ω); the tenth group series resistance is composed of four 0.2Ω and one The 0.1Ω R16~R20 resistor units are connected in series to form a series resistance group of 0Ω~0.9Ω (interval value is 0.1Ω), forming the basic structure of the resistance value output of the resistor card. Then add the maximum value of the series resistor group resistance values of the hundreds, tens, units and tenths digits to 900+90+9+0.9=999.9, which can form a maximum value of 999.9Ω, and the minimum resolution is A resistance of 0.1Ω is given to the device.

The combination of each digit of hundreds, tens, units and tenths is the same, such as the combination of hundreds digit resistor. The hundred's resistor combination is composed of four 200Ω and one 100Ω resistor units connected in series to form a resistor combination of 0Ω to 900Ω (the interval value is 100Ω); disconnect the relay contact on the 100Ω resistor unit on the hundred's digit, and the 100Ω The resistor unit is connected to the series structure to form the output resistance. If the relay contact on the 100Ω resistor unit is closed, the 100Ω resistor unit is equivalent to a short circuit of 0Ω, and its 100Ω is not connected to the series structure to form the output resistance. Disconnect or connect the relay contacts on the line formed by the other four 200Ω on the hundreds position, which can connect or disconnect the corresponding 200Ω resistance unit from the series structure to form an output resistance; By combining the points of disconnection or connection, a resistance combination of 0Ω to 900Ω (interval value is 100Ω) can be obtained, or an arithmetic sequence resistance value with a difference of 100Ω and a range of 0Ω to 900Ω can be obtained.

When the relay contacts K31B, K31C, K32B, K32C, K21B, K21C, K22B, K22C, K11B, K11C, K12B, K12C, K01B, K01C, K02B, K02C are connected across resistors R5, R10, R15, and R20 When turned on, the theoretical value of the resistance output at both ends of RHi and RLo is the minimum value of 0Ω.

When all contacts of the relay connected across the resistor are disconnected, the resistance value output at both ends of RHi and RLo is the maximum value of 999.9Ω.

When the contacts of the relay connected across the resistor are selectively disconnected or connected as needed, the resistance value output at both ends of RHi and RLo is a certain resistance value between 0 and 999.9Ω, and the minimum change in resistance The amount is 0.1Ω.

The contacts of the relay connected across the resistor are connected with double poles, which can reduce the contact resistance of the relay contact at the short-circuited resistor by half. The resistance at the short-circuited contact is ≤0.015Ω to improve the output of the final resistance value. Accuracy.

The resistors with the above resistance value deviations are all shelf products, and only qualified products from resistor manufacturers must be used.

In order to obtain the target resistance value, the relay contacts need to be used to short-circuit the excess resistance value. At each bit of the series resistance group, that is, a certain power of the corresponding bit that is less than or equal to 9 times 10, the relay contacts are used to short-circuit the excess resistance value. The resistor realizes the target resistance, such as a single-digit series resistor group, and the relay contact short-circuit combination of the units-digit series resistor group achieves 1Ω or 2Ω or 3Ω or 4Ω or 5Ω or 6Ω or 7Ω or 8Ω or 9Ω to select the output. At the same time, the resistance at the short-circuit point of the segment is optimized. By using two groups of relay contacts in parallel, the contact resistance is halved. The maximum resistance value of a relay single contact is 0.03Ω. After using two groups of relay contacts in parallel, the contact short-circuit point Resistance ≤0.015Ω to improve the output accuracy of the final resistance value.

The given resistance is combined by the resistance of the hundreds-digit series resistor group, the tens-digit series resistor group, the units-digit series resistor group, and the tenth-digit series resistor group. Each resistance unit of the units-digit series resistor group and the tenth-digit series resistor group is Using 5 resistors of the same specification and resistance deviation in parallel, the resistance deviation of each resistor is ±0.01Ω, then the maximum resistance deviation of each resistor unit is reduced to ±0.01Ω/5 = ±0.002Ω; If a series-connected resistance group combination of units and tenths place obtains a resistance value output of 9.9Ω and the relay is fully turned off, the resistance deviation at this time is the maximum deviation of the units and tenths combination, that is, 10 × (± 0.002Ω) = ± 0.02Ω.

This variable resistor is controlled by a microcontroller system. The microcontroller calculates the number of relay short contacts through software and corrects the given resistance value. When outputting any resistance value from 0 to 999.9Ω, the hundreds digit relay group, tens digit relay group, units digit relay group, and tenth digit relay contacts are short-circuited according to the combination needs to achieve the output of the target resistance, and each resistance unit combination corresponds to The selection output of weight bits 1~9, the hundreds place relay group outputs (1~9)×10 ² Ω resistance, the tens place relay group outputs (1~9)×10 ¹ Ω resistance, the units place relay group outputs ( The resistance is 1～9)×10 ⁰ Ω, and the tenth place relay group outputs the resistance (1～9)×10 ^-1 Ω. There are corresponding closed combinations of fixed relay contacts. The output of each resistance value can count how many relays are in the closed state on the resistance output circuit. The final combined output resistance value of the resistance will be subtracted from the cumulative total of the relay closed contacts. resistance.

See Figure 2. In order to improve accuracy, in an optional embodiment, the typical correspondence relationship between the resistance values of each resistor unit through multiple resistors connected in parallel corresponds to R1 in Figure 1. The difference is that the 200Ω resistance of R1 is obtained by connecting five 1000Ω resistors in parallel; Similarly, other resistors are constructed in this way. Resistor units R1~R10 all use RJ711 high-precision alloy foil resistors. The combined resistance value of each resistor unit R1~R4 is 200Ω. Each resistor unit R1~R4 consists of 5 resistance units with a resistance of 1000Ω. The allowable resistance deviation is ±0.01 % resistors are connected in parallel; the combined resistance of the R5 resistor unit is 100Ω, which is obtained by connecting 5 resistors in parallel with a resistance of 500Ω and a tolerance of ±0.01%. The combined resistance of each resistor unit R6~R9 is 20Ω. Each resistor unit R6~R9 is obtained by connecting five resistors in parallel with a resistance of 100Ω and an allowable resistance deviation of ±0.01%. The combined resistance of the resistor unit R10 is 10Ω. , obtained by connecting five resistors in parallel with a resistance of 50Ω and a tolerance of ±0.01%.

R11~R20 all use RXJ3 type precision wire-wound resistors. The combined resistance of each resistor unit of R11~R14 is 2Ω. Each resistor unit of R11~R14 is composed of 5 resistors with a resistance of 10Ω and a tolerance of ±0.01Ω. Resistors are obtained by connecting them in parallel; the combined resistance of the R15 resistor unit is 1Ω, which is obtained by connecting five resistors with a resistance of 5Ω in parallel and a tolerance of ±0.01Ω. The combined resistance of each resistor unit R16~R19 is 0.2Ω. Each resistor unit R16~R19 is obtained by connecting five resistors in parallel with a resistance of 1Ω and an allowable resistance deviation of ±0.01Ω. The combined resistance of the R20 resistor unit is 0.1Ω, obtained by connecting five resistors in parallel with a resistance of 0.5Ω and a tolerance of ±0.01Ω.

See Figure 3. The single-chip computer controls the given resistance output of the variable resistor. Among them, the single-chip computer D1 can use a single-chip computer with model C8051F310. The low-power transceiver D2 can use a low-power transceiver with model MAX485ESA. The triggers D3, D5, D7 and D9 can use the flip-flop model 74HC273, and the drivers D4, D6, D8, and D10 can use the driver model MC1413P (BP). One asynchronous, full-duplex serial port UART0 of the microcontroller outputs an RS485 signal. Through the control lines P0.4 and P0.5 ports of the microcontroller D1 and the signal direction control terminal P1.7, the RS485 signal is output through the low-power transceiver D2. The low-power The transceiver D2 is connected to the host computer through the parallel resistor R21 at the output end, and sends the RS485 signal to the host computer. The microcontroller D1 receives the target resistance value input command from the host computer through the low-power transceiver D2. The control lines P1.2, P1.3, P1.4, and P1.5 of the microcontroller D1 are connected to the clock terminals CLK of the flip-flops D3, D5, D7, and D9 respectively. The parallel port lines P2 of the microcontroller are P2.0 and P2 respectively. 1. P2.2, P2.3, P2.4, P2.5, P2.6, P2.7 are connected to the 8-bit input terminals of flip-flops D3, D5, D7, and D9 at the same time. The flip-flops D3, D5, The 5-bit output lines of D7 and D9 are connected to the 5-bit input terminals of the driver D4, D6, D8, and D10 respectively. When the respective 5-bit output terminals of the driver D4, D6, D8, and D10 appear low level, the relay connected to the low level will form a circuit loop to energize the relay, and the relay will act. If the relay acts, it corresponds to the normally open state of the relay. The contacts will be closed, and the action of the relay will connect its contacts, ensuring that the resistance unit controlled by the relay contacts in Figure 1 is connected to or exits the output resistance loop. If pin 1 of D4 is high level, then pin 16 of D4 is reversely low level. The low level is connected to the negative terminal of the K31A relay. The positive terminal of the relay itself carries +12V positive electricity. At this time, the relay When the relay is electrically activated, the normally open contacts K31B and K31C on the relay are closed, the resistor R5 related to K31B and K31C is short-circuited, and the 100Ω resistance value of R5 is not connected to the entire resistance loop. Whether other resistance values on the line loop are connected to the entire resistance loop also depends on whether the normally open contacts adjacent to them are connected or disconnected.

The hundred relay group is controlled by K31A, K32A, K33A, K34A and K35A relays. The K31A relay controls the on or off of the K31B and K31C contacts. Similarly, the K32A relay controls the on or off of the K32B and K32C contacts. The K33A relay controls the on or off of the K33B and K31C contacts. The K33C contact is on or off, the K34A relay controls the K34B and K34C contacts on or off, and the K35A relay controls the K35B and K35C contacts on or off.

The ten-digit relay group is controlled by K21A, K22A, K23A, K24A, and K25A relays. The K21A relay controls the on or off of the K21B and K21C contacts. Similarly, the K22A relay controls the on or off of the K22B and K22C contacts. The K23A relay controls the K23B, K23B, and K22C contacts. The K23C contact is on or off, the K24A relay controls the K24B and K24C contacts on or off, and the K25A relay controls the K25B and K25C contacts on or off.

The units relay group is controlled by K11A, K12A, K13A, K14A and K15A relays. The K11A relay controls the on or off of the K11B and K11C contacts. Similarly, the K12A relay controls the on or off of the K12B and K12C contacts. The K13A relay controls the on or off of the K13B and K11C contacts. The K13C contact is on or off, the K14A relay controls the K14B and K14C contacts on or off, and the K15A relay controls the K15B and K15C contacts on or off.

The tenth place relay group is controlled by K01A, K02A, K03A, K04A and K05A relays. The K01A relay controls the on or off of the K01B and K01C contacts. Similarly, the K02A relay controls the on or off of the K02B and K02C contacts. The K03A relay controls the on or off of the K03B and K01C contacts. The K03C contact is on or off, the K04A relay controls the K04B and K04C contacts on or off, and the K05A relay controls the K05B and K05C contacts on or off.

When the variable resistor microcontroller system controls the work, when the microcontroller D1 receives the target resistance value input command of the host computer through the low-power transceiver D2, after the operation of the microcontroller, it forms control commands of hundreds, tens, everyone, and tenths respectively. , the control instructions for the hundreds, tens, everyone, and tenth digits enter flip-flops D3, D5, D7, and D9 respectively. The data of flip-flops D3, D5, D7, and D9 pass through the drivers D4, D6, D8, and D10 to make the relay corresponding The contacts are closed respectively to obtain the required resistance value output. The entire reception, processing and output time is completed within 0.3s, in which the motion stabilization of the relay is completed within 0.1s.

See Figure 4. The microcontroller control circuit receives the specific resistance value output control instructions from the host computer and decomposes them into control instructions corresponding to the hundreds, tens, individual and tenths resistance values. The instructions are converted into data and sent to D3, D5, D7, and D9 latches. The data of the D3, D5, D7, and D9 latches pass through the D4, D6, D8, and D10 drivers to determine the corresponding relays K31A, K32A, K33A, K34A, K35A, K21A, K22A, K23A, K24A, K25A, K11A , K12A, K13A, K14A, K15A, K01A, K02A, K03A, K04A, K05A are energized. The relay forming the circuit loop is energized to close the corresponding normally open contact. The closing or opening of the normally open contact of this series determines determines the final output resistance value.

See Figure 5. The schematic diagram of an arithmetic resistance series with a difference of 100Ω and a range of 0Ω to 900Ω. This picture serves as a representative, as do tens-digit resistor combinations, units-digit resistor combinations, and tenth-digit resistor combinations.

In the figure, the key relay contacts for each set of resistance output are:

The normally open contacts of K31B, K31C, K32B, and K32C are closed, and the output resistance is 0Ω;

The normally open contacts of K31B and K31C are open, the normally open contacts of K32B and K32C are closed, and the output resistance is 100Ω;

The normally open contacts of K31B, K31C, K33B and K33C are closed, the normally open contacts of K32B and K32C are open, and the output resistance is 200Ω;

The normally open contacts of K31B, K31C, K32B and K32C are open, the normally open contacts of K33B and K33C are closed, and the output resistance is 300Ω;

The normally open contacts of K31B, K31C, K34B and K34C are closed, the normally open contacts of K32B, K32C, K33B and K33C are open, and the output resistance is 400Ω;

The normally open contacts of K31B, K31C, K32B, K32C, K33B and K33C are open, the normally open contacts of K34B and K34C are closed, and the output resistance is 500Ω;

The normally open contacts of K31B, K31C, K35B, and K35C are closed, and the normally open contacts of K32B, K32C, K33B, K33C, K34B, and K34C are open, and the output resistance is 600Ω;

The normally open contacts of K31B, K31C, K32B, K32C, K33B, K33C, K34B, and K34C are open, and the normally open contacts of K35B and K35C are closed, and the output resistance is 700Ω;

The normally open contacts of K31B and K31C are closed, the normally open contacts of K32B, K32C, K33B, K33C, K34B, K34C, K35B and K35C are open, and the output resistance is 800Ω;

K31B, K31C, K32B, K32C, K33B, K33C, K34B, K34C, K35B, K35C normally open contacts are disconnected, and the output resistance is 900Ω.

The present invention is not limited to the above-mentioned embodiments. Anyone can produce various other forms of products under the inspiration of the present invention, but no matter any changes are made in its shape or structure, it does not deviate from the above-mentioned technical ideas of the present invention. Below, various substitutions and changes can be made based on the common technical knowledge and common methods in the art, and they should all be included in the protection scope of the present invention.

Claims (7)

1. A method of combining a given output resistance value in series and parallel, which is characterized in that: the given resistance is combined by resistors in hundreds, tens, units and tenths, and each of the ones and tenths of the resistance combination is The resistor units are all made of 5 resistors of the same specification and resistance value deviation connected in parallel. The resistance value deviation of each resistor is ± 0.01Ω; at least 4 200Ω and 1 100Ω resistor units are used at intervals of 100Ω. Connect in series to form a hundred-digit resistor combination with an arithmetic sequence resistance of 0Ω to 900Ω; with an interval of 10Ω, at least four 20Ω and one 10Ω resistor units are connected in series to form an access circuit with a range of 0Ω to 900Ω. A ten-digit resistor combination with an arithmetic series resistance of 90Ω; with an interval of 1Ω, at least four resistor units of 2Ω and 1 are connected in series to form a single-digit resistor with an arithmetic series resistance value of 0Ω to 9Ω that is connected to the circuit. Combination; with an interval of 0.1Ω, at least four 0.2Ω and one 0.1Ω resistor units are connected in series to form a tenth resistor combination with an arithmetic sequence resistance of 0Ω to 0.9Ω connected to the circuit; forming a hundred's digit , the maximum value of the tens, units and tenth place resistor combinations is added, the maximum value is 900+90+9+0.9=999.9Ω, and the minimum resolution is 0.1Ω resistor given device, and each adjacent two Between the series resistors, there are double-pole double switches connected in parallel on the series lines to switch on the relay, so as to realize the short-circuiting of the parallel resistor R contact and closing the contact resistance by half, corresponding to the selected output of 1 to 9, each time the resistance value The output of the variable resistor microcontroller system counts the number of relay short contacts on the resistance output loop, and the combined output resistance value will subtract the cumulative total resistance value of the relay closed contacts; the variable resistor is controlled by the microcontroller system, and the microcontroller calculates it through software The number of relay short contacts is used to correct the given resistance value; when outputting any resistance value from 0 to 999.9Ω, the hundreds digit relay group, tens digit relay group, units digit relay group, and tenth digit relay contacts are short-circuited according to the combination needs. When the resistance reaches the target resistance output, each resistor unit combination corresponds to the selection output of 1 to 9 weight bits, the hundreds digit relay group outputs (1 to 9) × 10 2 Ω resistance, and the tens digit relay group outputs (1 to 9) ×10 1 Ω resistance, the units relay group outputs (1～9)×10 0 Ω resistance, and the tenth place relay group outputs (1～9) For the closed combination of points, the output of each resistance value counts how many relays on the resistance output loop are in the closed state. The final combined output resistance value of the resistance will be subtracted from the cumulative total resistance value of the relay closed contacts; The microcontroller controls the given resistance output of the variable resistor. One asynchronous, full-duplex serial port UART0 of the microcontroller outputs an RS485 signal through the control line P0.4 and P0.5 port of the microcontroller D1 and the signal direction control terminal P1.7. The RS485 signal is output through the low-power transceiver D2. The low-power transceiver D2 is connected to the host computer through the parallel resistor R21 at the output end and sends the RS485 signal to the host computer; The microcontroller D1 receives the target resistance value input command from the host computer through the low-power transceiver D2. When the driver's respective 5-bit output terminal appears low level, the relay connected to the low level will form a circuit loop to energize the relay. If the relay acts, the normally open contact of the corresponding relay will close. The relay action will connect its contacts, and the relay contacts control the resistance unit to enter or exit the output resistance loop. 2. The method of combining series and parallel combinations of given output resistance values as claimed in claim 1, characterized in that: the hundred-digit resistance combination is a resistance combination of 0Ω~900Ω composed of four 200Ω and one 100Ω resistance units connected in series; When the relay contact on the 100Ω resistor unit on the hundreds digit is disconnected, the 100Ω resistor unit is connected to the series structure to form an output resistance. 3. The method for combining a given output resistance value in series and parallel as claimed in claim 2, characterized in that: if the relay contact on the 100Ω resistance unit is closed, then the 100Ω resistance unit is equivalent to a short circuit of 0Ω, then Its 100Ω is not connected to the series structure to form an output resistance. 4. The method for combining a given output resistance value in series and parallel as claimed in claim 3, characterized in that: disconnecting or connecting the relay contacts on the line formed by four 200Ω on the hundreds digit, and connecting the corresponding The 200Ω resistance unit is connected or disconnected from the series structure to form an output resistance; the disconnection or connection of multiple sets of relay contacts on it is combined to obtain a resistance combination of 0Ω to 900Ω, or a combination called a difference of 100Ω and a range of Arithmetic sequence resistance value from 0Ω to 900Ω. 5. The method for combining series and parallel combinations of given output resistance values as claimed in claim 1, characterized in that: when the contacts K31B, K31C, K32B, K32C, When K21B, K21C, K22B, K22C, K11B, K11C, K12B, K12C, K01B, K01C, K02B, K02C are connected, the theoretical value of the resistance value output at both ends of RHi and RLo is the minimum value 0Ω; when connected across the resistor When all relay contacts are disconnected, the resistance value output at both ends of RHi and RLo is the maximum value of 999.9Ω. 6. The method of combining a given output resistance value in series and parallel as claimed in claim 1, characterized in that: when the single-chip computer D1 receives the target resistance value input instruction of the host computer through the low-power transceiver D2, after the operation of the single-chip computer, respectively The control instructions for hundreds, tens, everyone, and tenths are formed, and the control instructions for the hundreds, tens, everyone, and tenths are entered into the flip-flops D3, D5, D7, and D9 respectively, and the flip-flops D3, D5, and D7 , D9 data, through the driver D4, D6, D8, D10, the corresponding contacts of the relay are closed respectively, and the required resistance value output is obtained. 7. The method for combining a given output resistance value in series and parallel connection as claimed in claim 1, characterized in that: the single-chip microcomputer control circuit receives the specific resistance value output control instructions of the host computer and decomposes them into hundreds, tens, everyone, and tens. The control command corresponding to the bit resistance value is converted into data and sent to the D3, D5, D7, and D9 latches. The data of the D3, D5, D7, and D9 latches pass through the D4, D6, D8, and D10 drivers to determine the corresponding Whether the relays K31A, K32A, K33A, K34A, K35A, K21A, K22A, K23A, K24A, K25A, K11A, K12A, K13A, K14A, K15A, K01A, K02A, K03A, K04A, K05A are energized, they will form a circuit loop. The relay closes its corresponding normally open contact. The closing or opening of the series of normally open contacts determines the final output resistance value.