RU2526195C2 - Multi-channel device for measurement of temperature - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: invention relates to measurement equipment and may be used in a system of thermal regulation and telemetry of spacecrafts (SC). A multi-channel device for temperature measurement comprises resistance thermometers (RT), master resistors (MR), the common point of which is connected to the common bus, a stable current generator (SCG), one of leads of which is connected to the common bus, three amplifiers, connected in series to it, a control circuit (CC), eight multi-position unipolar electronic switches (MPUES). The other lead of the SCG is connected to the pole outlet of the first MPUES. Position leads of the first and second MPUES are combined in pairs and connected to the RT. Position leads of the third and fourth MPUES are combined in pairs and via newly introduced chains of two serially connected calibration resistors are connected to the common bus. Pole leads of the second, fourth and fifth MPUES are combined together and connected to a non-inverting inlet of the first amplifier. Also the additional SCG is introduced, which is included between the common bus and the pole lead of the sixth MPUES. Position leads of the sixth and seventh MPUES are combined in pairs and connected to the MR. The pole lead of the seventh MPUES is connected to the inverting input of the first amplifier. The second amplifier is made with the amplification ratio switched eighth MPUES. Outlets of the CC are connected by permission inlets and addresses of all MPUES.

EFFECT: higher accuracy of measurement data.

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Description

The invention relates to measuring equipment and can be used in a system of thermal control and telemetry of spacecraft (SC).

Known multi-channel device for measuring temperature (SU 1229599), containing thermal converters, resistors, switches, current source, control unit, clock, memory, digital-to-analog converters, RS-flip-flops, delay circuit, OR circuit, RC circuits, diodes .

However, this device is not reliable enough, since it contains a large number of elements.

Closest to the proposed technical essence (prototype) is a multi-channel version of a single-channel device for measuring temperature (RU 2447412), containing a resistance thermometer (TS) and a reference resistor (ZR), the common point of which is connected to a common bus, a stable current generator (GTS) , four electronic keys (EC), a rectangular pulse generator (GUI), three amplifiers, two ECs are additionally introduced, an RC filter, ECs are divided into three EC groups, two ECs in each group - the first and second, control inputs of the first ECs of all groups EC p GUI are connected to the direct output, and the control inputs of the second EC of all EC groups are connected to the inverse GUI output, the GTS is connected between the device common bus and the EC inputs of the first EC group, the output of the first EC of the first group is connected to the input of the first EC of the second group and the TS, the output of the second The EC of the first group of ECs is connected to the input of the second EC of the second group of EC and SR, a storage capacitor is introduced, which is connected to the outputs of the EC of the second group of ECs with one output, and the other to the input of the first amplifier on an operational amplifier (OS), turned on according to the repeater circuit, the output of the first op-amp is connected to the input of the second amplifier to the op-amp, switched on by the inverting amplifier circuit, the output of the second amplifier is connected to the combined inputs of the EC of the third group, the output of the first EC of the third group of the EC is connected to the input of the first amplifier, the output of the second EC the third group of EC is connected to the input of the RC filter, the output of the RC filter is connected to the input of the third amplifier on the op-amp, the output of which is the output of the device.

The disadvantages of the prototype are:

- insufficiently high reliability due to the large number of elements, because the number of elements is multiplied by the number of channels;

- insufficiently high long-term accuracy due to the neglect of changes in the parameters of elements during their aging.

The aim of the invention is to simplify the device, improving reliability and long-term accuracy.

This goal is achieved by the fact that in a multichannel device for measuring temperature, containing resistance thermometers (TC), specifying resistors (ZR), the common point of which is connected to a common bus; stable current generator (GTS), one of the terminals of which is connected to a common bus; three amplifiers connected in series, the output of the last amplifier is the output of the device; control scheme (SU); additionally introduced eight multi-position single-pole electronic switches (MOEP); another GTS terminal is connected to the pole terminal of the first MEP; positional conclusions of the first and second MOEP are combined in pairs and connected to the vehicle; the pole terminal of the third MEA is connected to the pole terminal of the first MEA; positional conclusions of the third and fourth MECP are combined in pairs and connected through a newly introduced chain of two series-connected calibration resistors to a common bus; the connection points of the calibration resistors are connected to the positional terminals of the fifth MOEP; the pole conclusions of the second, fourth and fifth MECP are combined together and connected to the non-inverting input of the first amplifier, which is made instrumental; an additional GTS has been introduced, which is connected between the common bus and the pole terminal of the sixth MES; positional conclusions of the sixth and seventh MOEP are combined in pairs and connected to the SR; the pole terminal of the seventh MOEP is connected to the inverting input of the first amplifier; the second amplifier is made with a switchable gain of the eighth MOEP; the outputs of the control system are connected to the inputs of the permission and addresses of all the MES.

The drawing shows a functional diagram of a multi-channel device for measuring temperature.

A multichannel device for measuring temperature contains: eight multi-position single-pole electronic switches (MOEPs) 1-8 (in the figure they are shown as electromechanical switches for clarity, and in addition to not obscuring the picture, the connection of elements 9-12 is not shown in a three-wire circuit) ; resistance thermometers (TS) 9, specifying resistors (ZR) 10, the common point of which is connected to a common bus; stable current generator (GTS) 13, which is connected to a common bus and pole terminals MOEP 1 and 3; positional conclusions MOEP 1 and 2 are combined in pairs, and each MOEP 1, 2 is connected to the corresponding TS 9; MOEP position outputs 3 and 4 are connected in pairs and connected through a chain of two series-connected calibration resistors 11 and 12 to a common bus; the connection points of the calibration resistors 11 and 12 are connected to the positional terminals of the MOEP 5; GTS 14 is connected between the common bus and the pole terminal of the MOEP 6; MOEP 6 and 7 positioning leads are paired and connected to SR 10; pole conclusions MOEP 2, 4, 5 are combined and connected to the non-inverting input of the instrumental amplifier 15; the inverting input of the amplifier 15 is connected to the pole output of the MOEP 7; the output of the amplifier 15 is connected to the input of the amplifier 16, which is made with a switchable amplification factor 8; the output of the amplifier 16 is connected to the input of the output amplifier 17; control circuit (SU) 18, the outputs of which are connected to the inputs of the permission and addresses of all 1-8 MEP.

A multichannel device for measuring temperature works as follows: when power is applied and the device is in measurement mode, the SU 18 outputs to the addresses of all the MES 1-8 the signals of alternate polling of all temperature channels and resolution signals for all the MES, except 3-5, while the input of the instrumental amplifier will receive the following differential voltage at equal currents GTS 13 and 14

$$U_{\mathrm{at}x\mathrm{fifteen}}=(R_{t\mathrm{from}}-R_{sR})\cdot I_{g\mathrm{from}t},(\mathrm{one})$$

where R _tf is the current value of the resistance of the interrogated vehicle;

R _sp - the resistance of the interrogated SP, which determines the lower limit of the measuring range;

I _GST - GTS current.

Instrumentation amplifier 15 amplifies this voltage by a factor of K1 and converts it to unipolar. The output of the device will be unipolar voltage equal to

$$U_{\mathrm{at}sx}=(R_{t\mathrm{from}}-R_{sR})\cdot K_{\mathrm{one}}\cdot K_2\cdot K_3,(2)$$

where K ₁ is the gain of the instrumental amplifier 15;

K ₂ - gain of the amplifier with a switchable gain of 16;

K ₃ - gain of the output amplifier 17.

When calibrating, the SU 18 removes the resolution signal from MOEP 1 and 2 and outputs it to MOEP 3 and 4 or 5, when it is fed to MOEP 4, the resistors of the lower calibration point 11 are measured, and when it is fed to MOEP 4, the resistors of the upper calibration are measured points - a series connection of resistors 11 and 12.

When using precision resistors C2-29 V in the accuracy class of 0.05%, the instability guaranteed by the technical conditions for the resistors (see ОЖО.467.099 ТУ, l.11, clause 2.3.2.1.) With a total on-time of less than 2000 hours is ± 0.05%, if this time is exceeded, it increases to ± 0.5%, i.e. ten times, but by distributing these 2000 hours over the entire resource evenly, it is possible to maintain high accuracy of the device when calibration is introduced for the entire period of the spacecraft’s active existence.

The essence of calibration is that at the time of its implementation, the relation

$$R_{\mathrm{at}}-R_n/U_{\mathrm{at}}-U_n=R_t-R_n/U_t-U_n,(3)$$

where R _n - calibration resistance of the lower calibration point - resistors 11;

R _in - calibration resistance of the upper calibration point - the total resistance of the resistors 11 and 12;

R _t is the current value of TC 9;

U _in , U _n , U _t - the output voltage of the device at the upper and lower calibration points and the current value.

Transforming expression (3) to determine R _t (knowing R _t , we can determine the temperature from the calibration characteristic for a specific TS 9), we obtain:

$$R_t=(R_{\mathrm{at}}-R_n)(U_t-U_n)/U_{\mathrm{at}}+R.(\mathrm{four})$$

As the device ages, a bias voltage ΔU may appear and change to α-voltage transmission coefficient. We rewrite expression (4) taking into account the appearance of ΔU and α:

$$R_t=(R_{\mathrm{at}}-R_n)[(\alpha U_t+\Delta U-(\alpha U_t+\Delta U)]/\alpha U_n+\Delta U-(\alpha U_n+\Delta U)+R_n.(5)$$

In the expression (5), when the brackets are opened, ΔU are mutually subtracted, α is put out of the brackets in the numerator and denominator and reduced, and expression (5) takes the form (4), which indicates that the degradation processes do not influence the accuracy of the device at ideal R _n and R _in . The proposed device is simpler because it contains fewer elements and, therefore, its reliability is higher; ten times increased long-term accuracy of the device due to the introduction of calibration.

More than 100 devices were manufactured; all of them were distinguished by good repeatability, accuracy, and resolution of ± 0.005 ° С. The devices are assembled on the elements: K10-17C, C2-29 V, 1127KN6, 2S198E, 2P304A, 140UD1701ASAR, N5503XM5-171.

Of the patent information materials known to the applicant, no signs were found that are similar to the totality of the features of the claimed object.

Claims (1)

A multichannel device for measuring temperature, containing resistance thermometers (TC), specifying resistors (ZR), the common point of which is connected to a common bus; stable current generator (GTS), one of the terminals of which is connected to a common bus; three amplifiers connected in series, the output of the last amplifier is the output of the device; a control circuit (CS), characterized in that eight additional multi-position single-pole electronic switches (MOEP) are additionally introduced; another GTS terminal is connected to the pole terminal of the first MEP; positional conclusions of the first and second MES are combined in pairs and connected to the corresponding TS; the pole terminal of the third MEA is connected to the pole terminal of the first MEA; positional conclusions of the third and fourth MECP are combined in pairs and connected through a newly introduced chain of two series-connected calibration resistors to a common bus; the connection points of the calibration resistors are connected to the positional terminals of the fifth MOEP; the pole conclusions of the second, fourth and fifth MECP are combined together and connected to the non-inverting input of the first amplifier, which is made instrumental; an additional GTS has been introduced, which is connected between the common bus and the pole terminal of the sixth MES; positional conclusions of the sixth and seventh MOEP are combined in pairs and connected to the corresponding SR; the pole terminal of the seventh MOEP is connected to the inverting input of the first amplifier; the second amplifier is made with a switchable eighth MOEP gain; the outputs of the control system are connected by the inputs of the permission and addresses of all the MES.

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