SU922534A1

SU922534A1 - Digital temperature meter

Info

Publication number: SU922534A1
Application number: SU802933376A
Authority: SU
Inventors: Николай Иванович Грибок; Владимир Иванович Зорий; Владимир Иванович Пуцыло; Сергей Аркадьевич Савенко
Original assignee: Львовский Ордена Ленина Политехнический Институт Им.Ленинского Комсомола
Priority date: 1980-05-30
Filing date: 1980-05-30
Publication date: 1982-04-23

Description

(5) ЦИФРОВОЙ ИЗМЕРИТЕЛЬ ТЖПЕРАТУРЫ(5) DIGITAL MEASURING TZHPERATURY

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Изобретение относитс к термометрии и может быть использовано при построении цифровых измерителей температуры с использованием резистивныхThe invention relates to thermometry and can be used in the construction of digital temperature meters using resistive

датчиков.sensors.

Известно устройство дл измерени температуры, содержащее термометр сопротивлени , подключенный по трехпроводной линии св зи, два источника тока, входное устройство ёторичного прибора 1 .A device for temperature measurement is known, comprising a resistance thermometer connected via a three-wire communication line, two current sources, an input device of the secondary device 1.

Однако известное устройство имеет недостаточную точность, обусловлен-, ную вли нием дрейфов напр жений аналого-цифрового преобразовани и неидентичности токов источников тока.However, the known device has insufficient accuracy due to the effect of voltage drifts of analog-to-digital conversion and the non-identity of the current source currents.

Известно также устройство, содержащее резистивный датчик, подключенный по трехпроводНой линии св зи, два операционных усилител и источник стабильного тока 21.It is also known a device containing a resistive sensor connected over a three-wire communication line, two operational amplifiers and a source of stable current 21.

Недостаток устройства заключаетс в том,, что на результат из-- ерени вли ют входные дрейфы усилителей и нестабильность тока источника тока.The disadvantage of the device lies in the fact that the input drifts of the amplifiers and the instability of the current of the current source affect the result of the transfer.

Наиболее близким к предлагаемому по технической суи ности и достигаемому результату вл етс устройство дл измерени температуры, содержа щее термометр сопротивлени , один из выводов которого первым проводом линии св зи соединен с зажимом источника тока, а вторым проводом - с об10 разцовым резистором, аналоговые ключи , усилитель посто нного тока, генератор линейно-нарастающего напр жени , схему переключени генератор квантующих импульсов, временный The closest to the proposed technical sufficiency and the achieved result is a temperature measuring device containing a resistance thermometer, one of the conclusions of which is connected to the clip of the current source by the first wire of the communication line and analog switches to the second wire, direct current amplifier, linearly-rising voltage generator, switching circuit, quantizing pulse generator, temporary

15 селектор, цифровой счетчик с индикацией 31 .15 selector, digital meter with indication 31.

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Однако известное устройство имеет недостаток, заключающийс в необ20 ходимости четырехпроводной линии св зи. Имеет недостаточную, точность, вследствие необходимости работы устройства в различном динамическом 39 диапазоне входных напр жений в первом и втором.такте измерени . Действительно, если интервал времени между срабатывани ми схемы срав нени равен. Т I:(RO- R|) + ли, К, - I(Rt ))AUjK2. где 5 - ток истечени тока; R,Rj - сопротивление термометра и образцового резистора соответственно; RJ - сопротивление линии св зи; AUt,AU2 дрейфы напр жений клю- чей; Kj ,К.2 коэффициенты преобразований при первом и втоI ром тактах измерений. Т.е., как видно из последнего выражени , неравенство коэффициентов К и Kj приводит к погрешности, равной А :tRo(K,-K2), (KI-K) + + ли, К, - . 8 предлагаемом же устройстве погрешность измерени определ етс выражением А« 3(Ri-R.5)K,, (3) где R и R - сопротивление замкнутых ключей переключате л в первом и втором тактах, а коэффициент К, вследствие работы аналого-цифрового преобразовател в узком диапазоне, вл етс по сто нным дл 2-х тактов . t paвнивa выражени (3) с (1), видно, что в предлагаемом устройстве погрешность .значительно ниже и определ етс разностью остаточных сопротивлений ключей переключател . Цель изобретени - повышение точности измерени , упрощение устройства . Поставленна цель достигаетс тем что устройство, содержащее термометр сопротивлени , один из выводов которого первым проводом линии св зи сое- 50 ни .However, the known device has the disadvantage of having a four-wire communication line. It has insufficient accuracy due to the need for the device to operate in a different dynamic 39 range of input voltages in the first and second measuring step. Indeed, if the time interval between the operation of the comparison circuit is equal. T I: (RO- R |) + li, K, - I (Rt)) AUjK2. where 5 is the current flow of the current; R, Rj is the resistance of the thermometer and reference resistor, respectively; RJ is the resistance of the communication line; AUt, AU2 key voltage drifts; Kj, K.2 conversion factors at the first and second measurement cycles. That is, as can be seen from the last expression, the inequality of the coefficients K and Kj leads to an error equal to A: tRo (K, -K2), (KI-K) + + li, K, -. 8 of the proposed device, the measurement error is determined by the expression A 3 3 (Ri-R.5) K ,, (3) where R and R are the resistance of the closed keys of the switch в in the first and second cycles, and the coefficient K, due to the operation of the analog-digital The transducer is in a narrow range and is equal to 2 clocks. t equals (3) with (1), it can be seen that in the proposed device the error is much lower and is determined by the difference in residual resistances of the keys of the switch. The purpose of the invention is to improve the measurement accuracy, simplify the device. The goal is achieved by the fact that the device contains a resistance thermometer, one of the conclusions of which is the first wire of the communication link.

динён с зажимом источника тока, вторым проводом - с образцовым резистором , аналого-цифровой преобразователь , блок индикации и блок управлени , один из выходов которого св зан с управл ющим входом аналого-цифрового преобразовател , в него введены реверсивный счетчик и переключатель,A terminal with a current source terminal, a second wire with a sample resistor, an analog-to-digital converter, a display unit and a control unit, one of the outputs of which is connected to the control input of the analog-digital converter, a reversible counter and a switch are inserted into it,

Claims

The device works in two cycles. In the first measurement cycle, the control unit 10 sets the switch 6 to the position I, and the reversible 55 counter to the zero state. At the same time; To the input of the analog-digital converter 8, a voltage is applied, which is converted to proportional 4 whose moving contact is connected to another terminal of the current source and to the input of the analog-digital converter, and the other two fixed contacts of the switch are connected to the third wire of the communication line and with another output of the reference resistor, respectively, and the output of the analog-to-digital converter is connected to the inputs of the reversing pulse counter, and the additional outputs of the control unit are connected to the control the main inputs of the switch and reversible pulse counter. The drawing shows a diagram of the device. The digital temperature meter contains a resistance thermometer 1, connecting wires 2-4, an exemplary resistor 5, a switch 6, a current source 7, an analog-digital converter 8, a reversal estimator 9 pulses, a control unit 10, an indication unit 11. The thermoelectric center of resistance 1 is connected via wire 2 to one of the fixed contacts of switch 6, the other fixed contact of which is connected through an exemplary resistor 5 to another wire of communication line 3, the second terminal of which is connected to the common connection point of the second resistance thermometer and the third wire of communication line k, the other end of which is connected to the current source 7 and one of the inputs of the analog-digital converter 8. The movable contact of the switch 6 is connected to another terminal of the current source 7 and the other input m analog-to-digital converter 8, the output of which is connected to the inputs of the reversible counter 9 pulses, and the output of the latter is connected to the input of the display unit 11, and the control inputs of the switch 6, analog-digital converter 8 and the reversible counter 9 pulses are connected to the corresponding outputs of the block 10 control number of pulses. The number recorded in the reversible pulse counter at the end of the first cycle will be equal to Nt (,, - f) t id1 where I is the current of the current source 7; K is the conversion factor of the analog-to-digital converter; 1 thermometer resistance; and RA are the resistances of wires 2 and; driven to the input to the drift analog-to-digital converter. In the second cycle, the control unit sets the switch to position P, and the reversible counter to subtract mode. In this case, the voltage applied to the input of the analog-to-digital converter, pre-. generated in the number of pulses:, 4-RAJ + RA.) Uap where RQ is the resistance of the reference resistor; RA is the resistance of wire 3. Since RJ. RO (1 t c.t), then when the RO o L Kl2 relations are fulfilled, the result recorded in the reverse pulse counter at the end of the second measurement cycle will be equal to N NI - N2. As can be seen from the last expression, the result of measurement is proportional to the measured temperature and does not depend on the resistances of the wires of the communication line, the drifts of the analog-to-digital conversion voltage. The device has a high measurement accuracy due to the fact that the measurement result does not depend on the drifts of the analog-digital converter voltage, since the drift voltage is present in two cycles of operation, and its influence on the measurement result is excluded. At the same time, the dynamic range of operation of the analog-digital converter is significantly reduced due to the fact that during both measurement cycles, comparable voltages are applied to its input. In comparison with the known device, the dynamic range is reduced by more than 2 times, since in the known device in the first cycle the voltage proportional to the sum of the resistances (Rj t) and in the second (RJ RA) are converted into code. In the proposed device, the voltage proportional to (Rj-t 2R) is applied to the input of the analog-to-digital converter in the first cycle, and in the second (Rgt 2R ;,). Narrowing the dynamic range of the analog-to-digital converter results in an increase in the measurement accuracy, as a result of which the errors of the first and second measurement cycles are the same and are eliminated as a result of subtraction. In addition, the introduction of a pulse counter and switch into the device allows a 25% reduction in the number of wires in the communication line. The invention includes a digital temperature meter containing a resistance thermometer, one of the terminals of which is connected to the terminal of the current source by the first wire of the communication line, the sample resistor to the second wire, the analog-to-digital converter, the display unit and the control unit, one of the outputs of which is connected with an A / D converter input. l, characterized in that in order to improve measurement accuracy and simplify the device, a reversible counter and a switch, the movable contact of which is connected to another terminal of the current source, and the input of an analog-to-digital converter, are inserted into it, and two other fixed contacts of the switch are connected to the third the wire of the communication line and with another output of the reference resistor, respectively, and the output of the analog-digital converter is connected to the inputs of the reversible pulse counter, and the additional outputs of the control unit tim with the control inputs of the switch and the reversible pulse counter. Sources of information taken into account in the examination of the USSR. USSR Author's Certificate No., cl. G 01 K 7/16, 1977.

2. For the application of the Federal Republic of Germany No. 2 4 + 7b29, j, G 01 K 1/02, published. 1976.

3. USSR author's certificate No. 556351, cl. G 01 K 7/10, - 1977 (prototype).

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