SU1377625A1 - Method of determining parameters of heat inertia of thermal resistance converter - Google Patents

Abstract

This invention relates to thermometry. The purpose of the invention is to improve the accuracy of determining the thermal inertia index by reducing the effect of high frequency interference. In the device implementing the method, the thermal converter is overheated by an electric current of a predetermined value, which is achieved by inserting an additional resistor 3 in the bridge arm and turning on the heating current until the bridge balance is reached. The next stage includes heating current and an additional resistor 3. The bridge imbalance voltage is removed from the output of the bridge circuit, which is fed to the input of the integrator 8 and has the polarity required to discharge the integrator 8. It is possible to state that the interval required to zero the integrator 8 is equal to the thermal inertia index of the thermal converter. 2 Il. WITH/)

Description

ipue one

The invention relates to a measurement technique, mainly to thermometry, where the measurement of the thermal inertia (thermometer) index of thermometers is of both self-interest (in temperature measurements under non-stationary conditions) and applied, which is associated with an estimate of the values PTI (heat capacity5 heat transfer coefficient).

 of the invention, an increase in the accuracy of determining the thermal inertia indicator due to 5 less influences of high-frequency interference.

Fig. 1 shows a diagram of a device 5 that implements the proposed method for determining PTI | 2, time diagrams of the device operation.

The device (Fig. 1) contains a power source 1 connected to a bridge circuit 5 incorporating a resistor thermoconverter 2 an additional resistor 3s switch 4, a switching resistor 3; and resistors Sj 6 and 7. Measuring the diagonal of the bridge is connected to the integrator 8, the output of which through the comparator 9 is connected to the timer 10,

The method for determining PTI is as follows.

At the first stage, by manually balancing the bridge circuit using a resistor 5, the resistance of the thermal converter 2 is compensated at an ambient temperature TO

At the second stage, the thermal converter 2 is overheated by an electric current for a predetermined amount uR by switching the bridge arm in series with the thermal converter 2 of the additional resistor 3 and switching on the heating current until the bridge balance is reached. At the same time, the resistance of the thermal converter UR (with a negative TKS thermal converter).

At the third stage, the heating current and the additional resistor 3 are switched on. The process of ostigoani thermoelectric converter to the previous value occurs.

R,

by exponential

; t T

his resistance to law

R (t) R ,, -UR e where T is the index of thermal inertia of the thermal converter

The voltage of the bridge imbalance is removed from the output of the bridge circuit, which also changes exponentially

and

 I.

Ur e

Out the bridge

value of measuring current:

U R .- the thermal transducer overheating value set by the resistance of the resistor 3. At this stage, the integrator 8 integrates the transient process of free cooling of the TP to the previous value of R (Fig. 2d). By the end of the integration, the voltage value at the integrator output is i

and

EXIT, INT

dt

 Ie.iuR

where Vy is the time integrator constant.

After the resistance of the thermocouple is reached, the value of R includes an additional resistor 3. At the same time, the voltage unbalance, equal to I uR, is fed to the input of the integrator and has the polarity required to discharge the integrator. Based on the law of conservation of charge, it can be argued that the time interval required for zeroing the integrator is noKasaTejBo of the thermal inertia of the thermal converter (Fig. 2c, d).

1a

uRto

 G „

loARC

In the description of the method and timing diagrams, it was assumed that the thermal coefficient of resistance of the thermal converter is negative. With a positive TCS TP, it is enough to invert the operation diagram of the key 4, which commits additional resistor 3, or transfer the additional resistor with the key, which commutes, to the adjacent arm of the bridge circuit.

Claims (1)

Invention Formula The method for determining the thermal inertia index of a resistance thermocoupler, according to which The resistors are balanced in a bridge circuit with a thermal converter and a switched additional resistor at ambient temperature and an additional resistor switched off, rebalanced by heating the thermal converter when the additional resistor is switched on, and the heating of the thermal converter is turned off, so that the accuracy of determining the thermal inertia index by reducing the influence of interference, integrate the output signal of the bridge circuit during the cooling process when the additional resistor is turned off, then integrate with a reverse sign, the voltage proportional to the specified resistance value, which is overheated, until zero conditions are reached, the integration time is measured with the opposite sign, the value of which is equal to the thermal inertia of the thermal converter. S & WA. 2