RU2682080C1 - Method for measuring temperature, pressure and density section in liquid - Google Patents

Abstract

FIELD: manufacturing technology.SUBSTANCE: invention is intended for use in oceanology and can be used in other areas. Essence of the invention lies in the fact that distributed thermal section gauges are used, each containing n modulated by line sensitivity for the functions {<p, (z)},of conductors. Three thermal section gauges with different temperature (α) and strain-gauge (β) sensitivity. They are put in a common soft shell and set in the medium along the measured section. Resistance of the conductorsis measured and the temperature section θ{z), pressure P(z) and density ρ(z) is determined by the formulas:,,, where z is the spatial coordinate along the profile (in particular, depth);, b– decomposition coefficients θ(z) and P(z) by the basis of orthogonal functions {ϕ(z)},,and the coefficientsand bare determined from the solution of n systems of equations of the type of αa+βb+αβc=R(i, j),, wherefor j=0;for;R– integrated measured resistance of the 0th conductor (unmodulated) of the i-th section gauge; R– integrated measured resistance of j-th conductor, modulated by the function ϕ(z) with amplitude rrelated to the constant component r; R– equivalent conductor resistance of the i-th profiler with constant linear resistance runder initial conditions; dP(z)/dz is the derivative with respect to the pressure section at the point z; g(ϕ, z) – acceleration of free fall depending on the geographical latitude of the place ϕ and the depth of the point z on the section.EFFECT: simultaneous measurement of temperature, pressure and density sections with increased accuracy.1 cl

Description

The invention relates to measuring equipment, is intended for use in oceanology and can be used in other fields. One of the main goals of expeditionary oceanological research is to obtain vertical profiles of temperature and density in coordinates of temperature-depth and density-depth, which are necessary for use in modern thermodynamic models [Guide to hydrological work in oceans and seas. L .: Hydrometeoizdat. 1977. 725 p.].

The density of sea water in modern mass measurements is not directly measured in the medium, but is calculated by the equation of state from the combined measurements of electrical conductivity, temperature and pressure, or the speed of sound, temperature and pressure. The ocean equation of state associates these values with an error of thousandths of a percent (last update TEOS-10) [IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. (Available from http: www.TEOS-10.org)]. However, for coastal waters and seas, it has amendments that are periodically updated and will be updated in the future. It is desirable to exclude the use of the equation of state of sea water from the method for determining the density profile.

The method of obtaining CTD (electrical conductivity, temperature, pressure) profiles by sounding from the ship at oceanological stations also contains a methodological error of temporal variability (up to several percent for several hours of sounding), which is ignored in the adopted measurement technology.

The method for measuring discrete instantaneous profiles of hydrophysical quantities using garlands of point meters located at several horizons on the suspensions of buoy stations contains a significant sampling error, since there are not many meters at the horizons.

Known meters instantaneous temperature profile, thermal profiles [A.S. 808872 USSR, G01K 7/00. Device for measuring temperature. V.A. Gaisky. Publ. 02/28/1981. Bull. No. 8], using distributed temperature sensors, the linear thermal sensitivity of which is modulated by functions from the orthogonal basis. Since the temperature sensors are sensitive to pressure, their protection against pressure is required to eliminate errors from the strain effect. This leads to an increase in thermal inertia and an increase in dynamic error.

Known gauges for the profile of elastic deformations using distributed strain gauges with modulation of linear strain sensitivity also according to functions from the orthogonal basis [A.S. 937998 USSR, G01B 7/18. Device for measuring elastic deformation of structures. V.A. Gaysky, A.T. Gopko, A.K. Erokhin, I.Yu. Nemesh. Publ. 06/26/1982. Bull. No. 23]. However, such distributed strain gauges have a sensitivity to temperature and it is necessary to exclude errors from the influence of temperature.

The aim of the invention is to provide simultaneous measurement of instantaneous temperature, pressure and density profiles with increasing accuracy by eliminating the temperature measurement error from the strain effect and reducing dynamic error by reducing the thermal inertia and eliminating the error from the influence of temperature when measuring pressure.

A prototype of the proposed method was not found.

и тензо

чувствительности и с погонными функциями чувствительности к температуре и давлению каждого из n проводников, которые промодулированы по функциям из ортогонального базиса {ϕ_j(z)},

, помещают их в общую мягкую оболочку и устанавливают в среде вдоль траектории измеряемых профилей θ(z) и P(z), измеряют интегральные сопротивления проводников

и определяют профиль температуры по формулеThis goal is achieved by using three distributed profilers of conductors with different temperature coefficients

and tenzo

sensitivity and with linear functions of sensitivity to temperature and pressure of each of n conductors, which are modulated by functions from the orthogonal basis {ϕ _j (z)},

place them in a common soft shell and install them in the medium along the trajectory of the measured profiles θ (z) and P (z), measure the integral resistances of the conductors

and determine the temperature profile by the formula

,

,

,pressure profile according to the formula

,

The density profile according to the formula

,

,

; b_j - коэффициент разложения профиля давления P(z) по базису ортогональных функций {ϕ_j(z)},

, причем коэффициенты a_j и b_j определяются из решения n систем уравнений

видаwhere z is the spatial coordinate along the profile (in particular, depth); a _j is the coefficient of expansion of the temperature profile θ (z) along the basis of orthogonal functions {ϕ _j (z)},

; b _j is the expansion coefficient of the pressure profile P (z) along the basis of orthogonal functions {ϕ _j (z)},

and the coefficients a _j and b _{j are} determined from the solution of n systems of equations

kind of

α _i a _j + β _i b _j + α _i β _i c _j = R (i, j),

для j=0;

для

;Where

for j = 0;

for

;

R _i0 is the integral measured resistance of the 0th conductor (unmodulated) of the i-th profiler; R _ij is the integral measured resistance of the jth conductor, modulated functions ϕ _j (z) with amplitude r _im against the background of the constant component r _im ; R _im is the equivalent resistance of the conductor of the i-th profiler with a constant linear resistance r _im under initial conditions; dP (z) / dz is the derivative with respect to the pressure profile at the point z; g (ϕ, z) is the acceleration of gravity depending on the geographical latitude of the place ϕ and the depth of the point z on the profile.

Consider the rationale for the proposed method. We believe that for a resistor sensor with known coefficients of temperature sensitivity θ for resistance α and compressibility β for pressure P, the equation for resistance

where R ₀₀ is the known initial resistance of the sensor at the initial (zero 0 ° C) temperature and atmospheric (zero P = 0) pressure.

The sensor distributed along z will perceive the profiles θ (z) and P (z) depending on the modulation of the linear sensitivity to θ and P. To restore θ (z) and P (z), it is convenient to use the expansion of the profiles θ (z), P (z ) and θ (z) P (z) with respect to the functions ϕ _j (z) from the orthogonal basis {ϕ _j (z)},

To determine each of the coefficients a _j , b _j and c _j , a separate wire sensor with linear sensitivity modulated according to R ₀₀ according to the function ϕ _j (z) is used.

The function ϕ ₀ (z) = 1, i.e. distributed wire sensor to determine a ₀ , b ₀ and c ₀ does not have modulation and has linear resistance

Then we write for resistances

and 0th conductor

where L is the length of the conductor.

Expand the expression (8)

Consider the terms of expression (9)

From the expression (9), substituting (10-13), we obtain

.To determine the unknowns a ₀ , b ₀ and c ₀ , three distributed conductors with different α _i , β _i

.

For three distributed conductors, we obtain three equations of the form (14), which we represent as a system of linear algebraic equations with three unknowns

The determinant of the system has the form

And the system has a solution regarding the unknowns a ₀ and b ₀ , unknown c ₀ it is not necessary to find.

, являющимися знакопеременными, примемWhen modulating R _{i0 with} respect to the functions ϕ _j (z) for

which are alternating, we accept

and get

Expand expression (18)

Consider the terms of expression (19)

;

;

;

;

;

;

;

;

;

;

;

;

.

.

Rewrite Expression (19)

Given (15),

we obtain from (21)

.where R _ij is the measured resistance of the j-th conductor of the i-th profiler, modulated by the function ϕ _j (z); R _i0 is the measured resistance of the 0th conductor of the i-th profiler, modulated by the function ϕ _j (z) = r _im ; R _im - resistance of the conductor with an average modulation level r _im j-x conductors

.

. Поскольку

, т.е. 2⋅(n-1) неизвестных определяются из (n-1) систем уравнений вида (23), определитель (16) всех систем один и тот же.Further, the unknowns a _j and b _{j are} determined from the solution of the system of three equations (23) for

. Insofar as

, i.e. 2⋅ (n-1) unknowns are determined from (n-1) systems of equations of the form (23), the determinant (16) of all systems is the same.

, θ(z) и P(z) по ортогональным функциям {ϕ_j(z)} определены и можно использовать формулы (2) и (3). При использовании способа предполагается, что коэффициенты α_i и β_i известны из справочных данных для конкретных материалов проводников. Однако эти значения могут быть неточными, поэтому целесообразно их определить при градуировке. Для этого каждый распределенный профилемер надо поместить в три различных состояния известных температуры и давления, для формирования системы уравнений вида, например,Thus, all the expansion coefficients a _j and b _j ,

, θ (z) and P (z) with respect to the orthogonal functions {ϕ _j (z)} are defined and formulas (2) and (3) can be used. When using the method, it is assumed that the coefficients α _i and β _{i are} known from the reference data for specific materials of conductors. However, these values may be inaccurate, so it is advisable to determine them during calibration. To do this, each distributed profiler must be placed in three different states of known temperature and pressure, to form a system of equations of the form, for example,

,

,

,

,

и

.where R _i01 , R _i02 , R _i03 - resistance of the conductor of the 0th unit at different

and

.

The solution of three systems of three equations, each of the form (24), with a common determinant

gives values α ₁ , α ₂ , α ₃ and β ₁ , β ₂ , β ₃ .

To determine the density profile ρ (z), we use the hydrostatic equation [Zaburdaev V.I., Gaysky V.A. Practical formulas for the relationship of pressure and depth in the Black Sea. Marine hydrophysical journal. 2002. No.6. S. 16-17; Ocean dynamics. Edited by Yu.P. Doronin. L .: Hydrometeoizdat. 1980. 304 p.].

where g (ϕ, z) is the acceleration of gravity, depending on the geographical latitude of the place ϕ and depth z

Thus, we have simultaneously all three instantaneous profiles: temperature θ (z), pressure P (z) and density ρ (z).

Claims (10)

A method for measuring temperature, pressure and density profiles in a liquid using distributed profilers containing n modulated by linear sensitivity for functions from the orthogonal basis

conductors, characterized in that they use three distributed profilers of conductors with different temperature (α _i ) and tenso (β _i ) sensitivity

they are placed in a common soft shell and installed in the medium along the trajectory of the measured profiles, the integrated resistances of the conductors are measured

and determine the temperature profile by the formula

pressure profile according to the formula

density profile according to the formula

where z is the spatial coordinate along the profile (in particular, depth); a _j , b _{j are the} expansion coefficients of the temperature profiles θ (z) and pressure P (z) in terms of the basis of orthogonal functions

moreover, the coefficients a _j and b _{j are} determined from the solution of n systems of equations

kind of

Where

for j = 0;

for

R _i0 is the integral measured resistance of the 0th conductor (unmodulated) of the i-th profiler; R _ij is the integral measured resistance of the jth conductor modulated by the function ϕ _j (z) with amplitude r _im against the background of the constant component r _im ; R _im is the equivalent resistance of the conductor of the i-th profiler with a constant linear resistance r _im under initial conditions; dP (z) / dz is the derivative with respect to the pressure profile at the point z; g (ϕ, z) is the acceleration of gravity depending on the geographical latitude of the place ϕ and the depth of the point z on the profile.