SU1446494A1 - Method and apparatus for determining the index of thermal inertia of thermal frequency converters - Google Patents

Abstract

The invention relates to heat engineering measurements and makes it possible to improve the accuracy of determining the thermal inertia index of thermal converters with a frequency output signal by eliminating the method error due to a non-zero final value of the thermal converter frequency. The number of output pulses of the thermocouple is calculated in three equal successive time intervals with the subsequent calculation of the thermal inertia index using the calculation formula. A device that implements the method contains a generator of 2 clock pulses, a pulse shaper 1, logic circuits 4, 5 and 6, logarithmized reversing counters 7, 8, a distributor of 3 pulses., Subtracting 10 and dividing device 11, time crp converter 9 and block 12 digital display. 2 sec. f-ly, 1 ill. ((L

Description

QD

1-14

The invention relates to the field of heat engineering measurements and is intended to determine the thermal inertia index of frequency thermocouplers, for example, piezoquartz temperature converters, both in laboratory and in factory conditions.

The aim of the invention is to improve the accuracy of determining the index of thermal inertia of frequency thermocouples by eliminating the methodological error due to

non-zero steady-state value of the output frequency of the thermal converter. ,

The drawing shows a functional block diagram of a device that implements the proposed method.

The device contains a shaper 1 pulses, a generator of 2 clock pulses, a distributor of 3 pulses, three logical elements AND 4-6, two logarithmically reversible counters, 7 and 8, time - code converter 9, subtractive device 10, dividing device 11 and block 12

digital display.

The output of the imaging unit 1 is connected to the first inputs of three logical elements 4-6, the outputs of which are connected to the addition and subtraction inputs of the log reversing counters 7 and 8, and the outputs of the latter through the zazychayuschaya device 10 are connected to the vocal input of the separating device .11. generator 2. tact pulses connected to the input of the distributor 3 pulses, the first output of which is connected to the second input of the first logic element 4, the second output to the second input of the second logic element 5, the third output to the second input t etego AND gate 6 and to the input time code converter 9, and the fourth output - to the input of oscillator 2 Stop clock. The output time of the code converter 9 is connected to the second input of the dividing device 1 1, the output of which is connected to the digital 12 digital search and locator.

The method is carried out as follows.

The output of the frequency converter under investigation, the value of the heat index value of which is to be determined, is connected to the input

driver 1. drives and inlet. Start of generator 2 "A thermal pulse is applied to the thermal converter. During the period of regular thermal conditions, the output frequency F (c) of the thermal converter varies exponentially in time.

F. +

(F “F,) exp (- |) LR exp (-), (1)

g

0

five

0

five

 . 0

five

0

five

where the initial and final frequency of the temperature converter, respectively; F FH - F;

 C is an indicator of thermal inertia of a thermocouple; t - current wren.

The pulse shaper 1 converts the output frequency of the thermoconverter to rectangular W pulses, which, through logic gates AND 4-6, play the role of keys, controlled by signals from the corresponding Epix distribution outputs (Pulse 3, arrive in a certain sequence at the addition inputs and subtraction - logarithmic reversible counters 7 and 8.

A clock pulse generator 2 is triggered on the input. The trigger is triggered by a signal at the start of a regular thermal mode. The output pulses of the generator 2, received at the distributor 3, which is, for example, a ring register made on the trigger-line, appear alternately on the first, second, third and fourth outputs and arrive at the second inputs of logic gates And 4-6.

The duration ;; it of pulses at the outputs, of the distributor 3 is determined by the period of the clock, frequency of the generator 2. The fourth pulse of the distributor 3, the last one, arrives at the input of the Stop of the generator 2, turns it off and stops the device.

The input of the addition of the logarithmic reversible counter 7 through the logic element 4 during the action of the first pulse from the output of the distribution, body 3 with the duration d t receives N shuhls at

N 1 S F (t) dt + dFH tl 0

- exp (- -): j

(2)

During the second time interval, equal in duration to the first one, to the subtracting input of counter 7 via a logical

element

2dt5 enters N j pulses

N,

  F (t) clt + aFD 1 a-i

, 4t, -,, 4t V exp (-) Jexp (- -)

(3)

Since the counter 7 is made logarithmic, a code combination will be formed at its output proportional to the value ln (N - N). Similarly, the input of the addition of the logarithmic reversible counter 8 through the logic element 5 receives N pulses, and its subtracting input through the logic element 6 - N3 pulses

zl t

N3 J F (t) dc F,

t +

g & 1

I LT / 2ilt4 expC- -) J exp (- ---)

v .With

JF 0 t 1 - 25 (4)

at the output of counter 8, by the end of the third cycle, a code combination proportional to the value of In ().

Simultaneously, from the third output of the distributor 3, a pulse of duration ds arrives at the input of the time of the code converter 9 and is converted into a code combination received at the input of the dividing device 11. The second combination of the dividing device 11 is supplied with the difference of the code combinations

(3)

ln (N., - N.J) - ln (N g Nj)

, N, - N2

 inr, N 1 - N3

from the output of the subtractor 10.

The differences N., - N J and N 2 - N J do not contain a fixed final frequency value, since it is eliminated during the pulse subtraction process. The ratio of these differences in the number of pulses is

N 1 - N-z, m ,,,

,

The desired value of the thermal inertia index of the controlled thermocouple is calculated by the formula

t

Ni-N2

(7)

ten

15

20

25

thirty

The output signal of the dividing device 11 is the measurement result expressed by the relation (7) displayed by the digital display unit 12.

Claims (2)

1. The method of determining the thermal inertia index of frequency thermocouples, which consists in counting the output pulses of a thermocouple at the stage of regular thermal conditions in two equal time intervals following that, in order to improve accuracy, the number of output pulses of the thermocouple in the third is additionally calculated the time interval immediately following the second time interval and equal to it in duration, and the value of the thermal inertia indicator Former 1 is calculated by the formula L with 1n five 0 five 0 five where ds is the duration of each of three time intervals; Ni, N.i and N - the number of output pulses thermal converters counted in the first, second and third time intervals, respectively. 2. A device for determining thermal inertia indicators of frequency thermocouples, comprising a clock pulse generator, a pulse shaper, the output of which is connected to the first inputs of two logical elements AND, the outputs of which are connected to the addition and subtraction inputs of a logarithmically reversible counter, and a digital display unit that differs By the fact that, in order to increase the accuracy, a clock distributor, a third logical element AND, a second logarithm reversing counter, subtractive the device, the time-code converter and the separating device; the input of the pulse distributor is connected to the output of the clock pulse generator; the first output of the pulse distributor is connected to the second input of the first logical element I, the second, output to the second input of the second logic element I, the third the output is with the second input of the third logic element And and the input of the time-code converter, and the fourth output is with the control input of the clock generator, the first input of the third logic element and 64946 connected to the output of the pulse driver, the addition input of the second logarithm of this counter is connected to the output of the second logical element AND, and its subtraction input is connected to the output of the third logical element AND, the outputs of the first and second counters are connected to the inputs of the subtractor, 0 whose output connected to one of the inputs of the dividing device, to the second input of which the output of the time of the code converter is connected, and the output of the dividing device is connected to the digital display unit. Editor A.Vorovich Compiled by, Golubev Tehred M. Morgental Proofreader M. Vasiliev . Order 6740/47 Circulation 607 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5 Pronzyodst enio-printing company, Uzhgorod, st. Project, 4 Subscription