RU2534452C1 - Method of remote ambient temperature measurement - Google Patents

Abstract

FIELD: measuring instrumentation.

SUBSTANCE: light emitting device (LED or laser) is placed into environment for temperature measurement. Wavelength λ of light emitting device is measured, and Δλ difference between measured wavelength and known emission wavelength λ₀ of the same device at initial temperature T₀ is determined. Ambient temperature is calculated by the formula $$Tx=T0+\frac{hc\Delta \lambda }{B\lambda 0^2},$$

where h is Planck's constant, c is speed of light, B is constant of the material.

EFFECT: simplified method of ambient temperature measurement.

2 cl

Description

The invention relates to pyrotechnics and can be used for remote measurement of ambient temperature in various industries.

Known methods and devices for determining the temperature of the environment using contact thermocouples, thermal indicators, thermistors and circuits based on them. The use of thermocouples, thermistors, and temperature indicators is inefficient, in particular, the presence of electrical wires connecting the temperature sensor in the medium to the signal receiver is required.

Known methods for measuring temperature (Vlasov AB Electronics. - Murmansk: MSTU, 2007. - 153 p.), Based on the fact that the reverse current of the diodes changes with temperature. Therefore, knowing the functional dependence of the value of the reverse current (at a fixed blocking voltage) on the temperature of the semiconductor diode, we can estimate the temperature of the medium in which the semiconductor diode is placed.

The disadvantage of diode thermometers with measured reverse current is the strong nonlinear dependence of the measured current on temperature and its dependence on the magnitude of the voltage applied to the reverse-biased diode.

A known method of measuring temperature (Pat. RF No. 2089863, publ. 09/10/1997), which consists in the fact that a semiconductor diode placed in a medium with a controlled temperature, serves a constant voltage with different polarity, both opening and closing it pn- transition, set a specific value of the current through the transition, measure the forward voltage on the diode from the set current and determine the temperature T of the environment from the functional dependence.

The disadvantages of this method include:

1) the need to connect a voltage of different polarity to a semiconductor diode;

2) repeatedly reversing the polarity of the voltage applied to the diode to the opposite, in particular, measuring the reverse current through the pn junction at ambient temperature, further changing the polarity of the voltage applied to the diode, measuring the direct current through the pn junction, reducing the applied voltage until the direct reverse current;

3) the complexity of the measurement circuit, achieved by the fact that four diodes on a common substrate, a synchronous detector and a low-pass filter and other elements are introduced into the device;

4) the inability to remotely measure the temperature of the medium.

A known method of measuring temperature (Pat. RF No. 2410654, publ. 11/27/2011), in which the collection and processing of radiation, the selection of three spectral ranges and temperature estimation based on processing the values of wavelengths. This method of measuring temperature is the closest and adopted as a prototype.

The disadvantages of the method of measuring temperature based on the allocation of three spectral ranges include its complexity, including the complexity of mathematical processing.

The technical result, to which the claimed invention is directed, consists in simplifying the method.

To achieve the specified technical result, the claimed invention uses a light-emitting device, which is an LED or a laser, evaluate the radiation wavelength of the device and determine the change in wavelength and calculate the desired medium temperature.

Thus, remote temperature control is carried out by the pyrometric method using a light-emitting device - an LED, a laser, which acts as a new type of temperature sensor.

The invention consists in the following. It is known that when a direct bias voltage is applied to a light-emitting device in the bulk of the material, light radiation is generated due to the recombination of the main charge carriers in the pn junction region. The radiation wavelength λ is determined mainly by the magnitude of the band gap ΔE _s .

The band gap ΔE _s is related to the emitted wavelength λ as

$$\Delta E_s=hv=hc/\lambda ,\text{(one)}$$

where h is Planck's constant; v is the frequency; λ is the wavelength; c is the speed of light.

The value of ΔE _z depends on temperature: as the temperature decreases from T ₀ to T _{x the} band gap changes from ΔE _z0 to ΔE _zx (G. Gulyamov, H. Sharibaev. Effect of temperature on the band gap of a semiconductor // FIP (FIL) PSE, 2011, vol. 9, No. 1, vol. 9, No.1), moreover

$$B=\left(\Delta E_{sx}-\Delta E_{s0}\right)/\left(T_x-T_0\right);B=-\left(5...10\right)\cdot {10}^{-\mathrm{four}}\mathrm{uh}\mathrm{AT}/\mathrm{TO},\text{(2)}$$

where B is a coefficient depending on the type of semiconductor material, determined by known methods.

Therefore, with decreasing temperature, the wavelength λ of radiation decreases, and the radiation frequency increases.

Given the expressions (1) and (2), we can write:

$$B(T_x-T_0)=hc(\mathrm{one}/{\lambda }_x-\mathrm{one}/{\lambda }_0)=hc({\lambda }_0-{\lambda }_x)/{\lambda }_x{\lambda }_0=hc\Delta \lambda /[({\lambda }_0-\Delta \lambda ){\lambda }_0],\text{(3)}$$

where Δλ = (λ ₀ -λ _x ), while λ ₀ is the radiation wavelength at temperature T ₀ , λ _x is the radiation wavelength at temperature T _x .

Given the smallness of Δλ, expression (3) can be transformed:

$$T_x=T_0+hc\Delta \lambda /B{\lambda }_0^2.\text{(four)}$$

Expression (4) can be used to estimate the temperature of the medium in which the light-emitting diode is located.

The radiation wavelength λ ₀ and the change Δλ can be measured with a sufficient degree of accuracy by various known methods: by evaluating Newton's rings, using a diffraction grating, phase-shifting plates, using Fresnel biprism and others. With modern instruments, the change in the wavelength Δλ is estimated with high accuracy, reaching ± 1.0 ppm (± 0.001 nm at a wavelength of 1000 nm).

In this case, the light-emitting device acts as a temperature sensor of a new type, the physical parameters of which change with a change in the temperature of the medium.

To use a light-emitting device (LED, laser) as a temperature sensor, metrological tests of the calibration dependence λ = f (T) and an estimate of the value of the wavelength gradient Δλ / ΔT in the studied temperature range are preliminarily carried out.

The method is as follows.

Take a light-emitting device (LED or laser) and place it in the environment to measure its temperature. Observe the radiation of the light-emitting device using one of the above methods, determine the wavelength λ, evaluate Δλ, in comparison with λ ₀ at the initial temperature T ₀ and calculate the desired temperature T _{x of the} medium according to the formula: Tx = T ₀ + hcΔλ / Bλ ₀ ² . For example, taking into account that h is the Planck constant, h = 6.626 · 10 ^-34 Js, s is the speed of light; s = 3 · 10 ⁸ m / s and B = -10 · 10 ^-4 eV / K = 1.6 · 10 ^-22 J / K, λ ₀ = 550 nm = 550 · 10 ^-9 m at T ₀ = 300 K, Δλ = 40 nm = 20 · 10 ^-9 m, we have the desired temperature in the refrigerator:

T _x = 300-6.626 · 10 ^-34 · 3 · 10 ⁸ · 40 · 10 ^-9 / [1.6 · 10 ^-22 · (550 · 10 ^-9 ) ² ] = 300-164.3 = 135.7 K.

Thus, the change in the temperature of the medium is evaluated by the functional dependence of the wavelength of the radiation of the light-emitting device on the temperature λ = f (T).

Claims (2)

1. A method for remotely measuring the temperature of a medium based on measuring a wavelength of radiation from a light-emitting device placed in a test medium, characterized in that, as the medium temperature T _x changes _, the radiation wavelength λ _{x of the} light-emitting device is measured, the change in wavelength Δλ is calculated, and the temperature is estimated environment T _x according to the formula:

,
where T ₀ is the initial temperature of the medium; λ ₀ - radiation wavelength at temperature T ₀ ; h is Planck's constant; c is the speed of light; Δλ = (λ ₀ -λ _x ); λ _x - radiation wavelength at a temperature T _x ; B is the constant of the material. 2. The method according to claim 1, characterized in that an LED or a laser is used as the light-emitting device.