RU132539U1 - BRIDGE PRESSURE TENSOR CONVERTER TYPE - Google Patents

Abstract

A bridge-type strain gauge pressure transducer containing a strain gauge bridge that is connected to a stable current source, characterized in that it employs two instrumental amplifiers, the first inputs of which are connected to the midpoints of the tensor bridge struts, and their second inputs are connected to the midpoints of thermostable resistive dividers so that a separate amplification of the change in the potentials of the output diagonal of the tensor bridge is provided, and the outputs of the instrumental amplifiers are connected to the inputs of the analog-digital computer the second one determines separately the pressure and temperature of the measured medium according to the equations; where Δφ and Δφ are the amplified values of the change in the potentials of the output diagonal; K are the sensitivity coefficients of the strain gauge according to pressure; K are the sensitivity coefficients of the strain gauge according to temperature.

Description

The utility model relates to measuring technique and can be used in measuring both pressure and other physical quantities, the conversion of which into an electrical signal is carried out using strain gauge bridges.

As you know, see, for example, an article by D. B. Martynov and V. M. Stubniknikov “Temperature correction of pressure strain gauges based on SPS.” Sensors and systems. No. 10 of 2002, strain gauges have large temperature errors. To correct the multiplicative component of the temperature error, tensor bridge power from a stable current source is used. However, the additive component of the temperature error increases. In order to reduce the additive error, the elements of balancing the initial output signal of the tensor bridge are included in the strain gage and adjusted to the level determined by the equation

и

- входные сопротивления тензомостаWhere

and

- input impedance of the strain gage

и

- уходы начального напряжения моста

and

- departure of the initial bridge voltage

The balancing elements are performed by thermostable resistors, which are not placed on a pressure sensitive membrane. This method of thermal correction is used in a bridge strain gauge MIDA-01P. This transducer contains a strain bridge, which is powered from a stable current source. The output diagonal of its strain bridge is connected to the input of the instrumental amplifier, the output of which carries information about the pressure. This pressure transducer is selected as a prototype for the proposed utility model.

The main disadvantage of this prototype is the limitation of the thermal correction efficiency by different thermal conductivities of the bridge strain gages and balancing resistors. Moreover, they are placed in different temperature conditions. Therefore, at a dynamically changing temperature, the condition of thermal correction of the additive error is violated. Because of this, a prototype cannot be applied. For example, for measuring pressure in shock waves.

The purpose of the proposed utility model is to increase the efficiency of thermal correction of the additive component of the temperature error and, as a result, the expansion of the scope of bridge pressure strain transducers.

This goal, in a strain gauge containing a strain gage, which is powered from a stable current source, and which contains a tool amplifier, is achieved by introducing a second tool amplifier and an analog-to-digital computer. The first inputs of the instrumental amplifiers should be connected to the midpoints of the respective struts of the strain gage, and their second inputs are connected to the midpoints of the corresponding thermostable resistive dividers. The outputs of both instrumental amplifiers are connected in this case to the independent two inputs of the calculator., Which determines the temperature and pressure on the transducer membrane in accordance with the equations

;

;

where Δφ ₁ and Δφ ₂ are the output voltages of the first and second instrumental amplifiers, respectively, which are determined by the amplified deviations of the potentials of the output diagonal of the tensor bridge.

- коэффициенты чувствительности этих напряжений к изменению давления.K _p and

- the coefficients of sensitivity of these stresses to pressure changes.

- коэффициенты чувствительности этих напряжений к изменению температуры.K _t and

- coefficients of sensitivity of these stresses to temperature changes.

The equations are obtained on the basis of the mathematical model of a strain-bridge converter in which the bridge is powered from a stable current source.

·P+

·t°Δφ ₁ = K _p · P + K _t · t °; Δφ ₂ =

P +

T °

By calibrating the transducer by pressure and temperature, all four of its sensitivity coefficients are determined. For certain values of these coefficients, the equations of the transducer matmodel have unambiguous solutions.

Figure 1 shows a diagram of a utility model. Marked on it

! - transducer strain bridge

2 stable current source

3 - thermostable resistor dividers

4 - instrumentation amplifiers

5 - analog-to-digital computer

The operation of the converter is that with the help of two instrumental amplifiers and two resistor dividers, the changes of both potentials of the output diagonal of the strain gauge bridge, powered from a stable current source, are measured separately. This makes it possible to describe the transducer by a system of two equations, and thereby using a computer to separate the temperature and pressure of the medium acting on the membrane of the strain transducer.

Common features of the prototype transducer and transducer - utility model are supplying a tensor bridge with stable current and the use of instrumental amplifiers for measuring voltages. Distinctive features are the use of two instrumental amplifiers for the purpose of separately measuring the potentials of the output diagonal of the tensor bridge and the use of a pressure and temperature calculator. Thanks to the distinguishing features, together with the known ones, it was possible to increase the efficiency of thermal correction of the converter in dynamic temperatures. In addition, it became possible to measure not only pressure but also temperature with one strain transducer. Thus, to expand the scope of bridge strain gauges.

Claims (1)

A bridge-type strain gauge pressure transducer containing a strain gauge bridge that is connected to a stable current source, characterized in that it employs two instrumental amplifiers, the first inputs of which are connected to the midpoints of the tensor bridge struts, and their second inputs are connected to the midpoints of thermostable resistive dividers so that a separate amplification of the change in the potentials of the output diagonal of the tensor bridge is provided, and the outputs of the instrumental amplifiers are connected to the inputs of the analog-digital computer the second determines separately the pressure and temperature of the measured medium according to the equations $$P=\frac{\Delta {\varphi }_{\mathrm{one}}+\frac{K_t}{K_t^{\text{'}\text{'}}}\cdot \Delta {\varphi }_2}{K_p\left(\mathrm{one}+\frac{K_p^{\text{'}\text{'}}}{K_p}\cdot \frac{K_t}{K_t^{\text{'}\text{'}}}\right)}$$

; $${\text{t}}^{\circ }=\left(\text{Δ}{\varphi }_{\text{2}}+\frac{{\text{K}}_{\text{p}}^{\text{''}}}{{\text{K}}_{\text{p}}}\cdot \frac{\text{Δ}{\varphi }_{\text{one}}+\frac{{\text{K}}_{\text{t}}}{{\text{K}}_{\text{t}}^{\text{''}}}\cdot \text{Δ}{\varphi }_{\text{2}}}{\text{one}+\frac{{\text{K}}_{\text{p}}^{\text{''}}}{{\text{K}}_{\text{p}}}\cdot \frac{{\text{K}}_{\text{t}}}{{\text{K}}_{\text{t}}^{\text{''}}}}\right)\cdot \frac{\text{one}}{{\text{K}}_{\text{t}}^{\text{''}}}$$

, where Δφ ₁ and Δφ ₂ are the amplified values of the change in the potentials of the output diagonal; K _p and $$K_p^{\text{'}\text{'}}$$

- pressure transducer sensitivity coefficients; K _t and $$K_t^{\text{'}\text{'}}$$

- sensitivity coefficients of the strain gauge temperature.

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