A single arm bridge is different from a double arm bridge

1. The principle is different: there is only one bridge arm circuit inside the single bridge, and there is a double bridge.

There are two bridge arm circuits: the inner arm is used to measure the value of the resistance being measured, and the inner arm is used to eliminate the influence of lead resistance.

2. Different uses: single bridge is generally used to measure resistance above 10 ohms, and double bridge is generally used to measure resistance less than 10 ohms.

3. The number of buttons at the measuring end is different: two measuring ends on a single bridge and four measuring ends on a double bridge.

4. The measurement power supply is different: the general voltage of the single bridge is above 3V, and the current is small; The double bridge generally has a lower voltage and a larger current.

5. The internal structure is different: the three measuring bridge arms of a single bridge are generally independent structures.

The inner arm and outer arm of the double bridge need to be adjusted in tandem, and the resistance value is kept synchronous, and the structure is more complex than that of the single bridge.

6. In addition to the resistance of the bridge arm, the single bridge does not need another standard resistor; The double bridge requires the addition of standard resistors, some of which are internal and some are external.

7. Limited to the condition that the measurement current cannot be very large, the sensitivity of the double bridge is generally lower than that of the single bridge.

8. The double bridge generally needs to be connected by thicker wires, and the lead resistance is generally required to be no more than one-tenth of the measured resistance.

9. Additional: There is no obvious difference in the anti-interference ability of single bridge and double bridge, which is different from what kind of bridge.

It is related to the performance of the amplifier plate inside the bridge and the quality of the bridge.

1. Working principle: there is only one bridge arm circuit inside the single bridge, double bridge.

There are two arm loops, one for measuring the resistance value and one for eliminating the effect of the lead resistance.

2. Applicable conditions: single bridge is generally used to measure resistance above 10 ohms, and double bridge is generally used to measure resistance of 10 ohms and below.

3. Measuring end: The single bridge has two measuring ends, and the double bridge has four measuring ends. And the sensitivity of a single bridge is more sensitive than that of a double bridge.

4. Applicable measurement power supply: the general measurement voltage of a single bridge is above 3V; Twin bridges generally measure voltages below.

5. Circuit structure: The single-bridge measuring bridge arm is generally an independent structure.

No standard resistors are required; The inner arm and outer arm of the double bridge are adjusted by linkage, and the resistance value is synchronized, standard resistance needs to be added, and the connecting wire needs to be thick wire, and the structure is more complex than that of the single bridge.

Double-arm bridge <>

Single-arm bridge <>

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Original question: The sensitivity of the double-arm bridge is (d) times that of the single-arm bridge.

Double-arm bridges are generally referred to as Kelvin bridges. Kelvin (William Mthomson, 1st Baronkelvin, 1824-1907) was an Irish scientist. Kelvin bridge is a DC flat shirt balance double-arm bridge (referred to as double-arm bridge), which is a commonly used instrument for measuring low resistance (generally between 10 1) and has high measurement accuracy.

The similarities and differences between the double-arm bridge and the Wheatstone bridge are as follows:

Different applications: Wheatstone bridges are mainly used to measure median resistance (generally greater than 1 ohm and less than 1m ohm), while double-arm resistors are mainly used to measure low resistance (less than 1 ohm). The influencing factors are different:

A single-arm bridge is affected by the external loop resistance, while a double-arm bridge excludes the influence of the external loop resistance.

The equilibrium condition of the DC single-arm bridge is that the product of the resistance of the bridge relative to the arm is equal; Advantages of DC single-arm bridges: high sensitivity and high accuracy. The single-arm bridge is powered by a constant current source, so that the output of the bridge is not affected by temperature.

After the single-arm bridge detects the change of resistance, through the differential amplifier, the output signal is converted into the corresponding current through the conversion of voltage and current, and the current signal is compensated by the nonlinear correction circuit, that is, the DC4 20mA standard output signal with a linear relationship with the input signal is generated. Stress is applied to the semiconductor material, and in addition to the deformation, the resistivity of the material also changes. This phenomenon of changing the resistivity of a material due to stress is called the piezoresistive effect.

The single-arm bridge consists of 4 resistors, a working power supply, a galvanometer and a switch. When no current passes through the branch, the bridge reaches equilibrium.

A single-arm bridge is an instrument that can accurately measure resistance. Resistors R1, R2, R3, and R4 are called the four arms of the bridge, and G is a galvanometer to check whether there is current in the branch where it is located. When g passes through without current, the bridge is said to be balanced.

In equilibrium, the resistance of the four arms satisfies a simple relationship that can be used to measure the resistance.

The single-arm bridge is suitable for measuring the median resistance, and its principle circuit is shown in the figure. If the resistance is adjusted to an appropriate resistance value, no current can flow through the galvanometer G, that is, the potentials of the two points b and d are equal, which is called "bridge balance".

The bridge is a basic electromagnetism measuring instrument that uses the comparative method to measure physical quantities, and there are many types of bridges, if you want to measure the resistance of a larger resistance, a high-resistance bridge or a megohmmeter is generally used; To measure the resistance with a small resistance, a double-arm bridge is generally used, which has high accuracy and good stability.

Extended information: As a measurement circuit, a power supply is connected to one diagonal of the quadrilateral, and the other diagonal is connected to the zero instrument. Adjust the parameter values of some elements on the bridge arm so that the voltage at both ends of the finger zero instrument is zero, and the bridge reaches equilibrium. Using the bridge equilibrium equation z1z3=z2z4, the parameters of the measured component (e.g. resistance, inductance and capacitance) can be calculated from the values of the known components in the bridge arm.

Assuming that the four resistors are fixed, when S is closed, if it satisfies: "R3*R2=R1*R4", that is, the product of the diagonal resistances is equal, then UAD is equal to 0, that is, there is no voltage between ADs.

Using this principle, when one of the four quantities on both sides of the equation is an unknown quantity, if adjusting the values of the remaining three resistors makes the equation hold, then the unknown quantity can be obtained by using the formula. But in reality, as long as there is an adjustable variable resistor on each side of the equation, then one of the other two resistors is a fixed value, then the other one must be obtained.