RU4821U1 - THERMOMETER - Google Patents

Abstract

1. A thermometer containing an analog-to-digital converter, a digital display unit, a power supply and a direct current bridge, in the measuring arm of which a temperature sensor is included, in the adjacent arm of the first branch of the bridge - the first constant and first variable resistors, in the comparison arm, opposite to the measuring shoulder, the second constant resistor, and in adjacent to the measuring arm of the second branch of the bridge is a resistor, characterized in that the supply diagonal of the bridge is connected to a common analog output and voltage output of the power source an analog-to-digital converter, the analog inputs of which are connected to the measuring diagonal of the bridge, with the first constant and first variable resistors connected in series, and the terminals of the latter connected to the voltage inputs of the analog-to-digital converter, and the resistor adjacent to the measuring arm of the second branch of the bridge is made variable. 2. The thermometer according to claim 1, characterized in that the digital display unit is made in the form of a liquid crystal indicator.

Description

THERMOMETER

The inventive utility model relates to techniques for measuring temperature, namely to digital thermometers, and can be used in the design of portable temperature meters.

An analogue of the claimed utility model is a thermometer including a reference voltage source, a temperature sensor, supplying a voltage signal corresponding to the measured temperature, a transformer, switches that control the supply of a sensor signal and a reference voltage to the transformer primary winding, a double-integration analog-digital converter, transforming the voltage signal from the secondary winding transformer into digital signals and transmitting them to the digital information processing unit. The thermometer also contains a control channel for the switches, which provides control of the operation of the latter using the output signals of the digital information processing unit. This channel consists of converters that electrically isolate the switches from the digital information processing unit / Patent СМ No. 42IIII3, m, class. G- 01K 7/02, 1980 /,

The essential features of an analogue are a power source, a temperature sensor, an analog-to-digital converter, and a digital information processing unit coincide with the essential features of the claimed utility model.

The thermometer is characterized by measurement accuracy and the complexity of the design.

Another analogue of the proposed technical solution is a digital thermometer containing a constant voltage source, a constant current amplifier, mounted on an operational amplifier, whose feedback loop includes a temperature sensor, the resistance of which varies depending on temperature, an analog-digital converter of a push-pull integration system and an indicator on liquid crystals . A predetermined constant voltage is applied to the input of the DC amplifier. The output voltage of the amplifier is input into an analog-to-digital converter. The reference voltage of the converter is removed from the same power source as the constant voltage supplied to the input of the DC amplifier / Japan application N 55 33534, m, class G- 01 K 7/24, 1980 /.

The essential features of an analogue are a power supply, a temperature sensor, an analog-to-digital converter, and an indicator on liquid crystals coincide with s; natural features of the proposed device.

With high accuracy, this is a rather complicated device.

The closest analogue of the utility model is a thermometer containing a DC bridge, an analog-qi (| level transmitter operating on the principle of double integration with auto-zero correction and automatic detection of input signal polarity, a digital display unit and a power source. A temperature sensor is included in one of the measuring arms DC bridge, in the adjacent shoulder of the first branch of the bridge - parallel connected constant and variable resistors and a constant resistor connected in series with them, and two cm elshih shoulders of the second branch of the bridge - constant resistors

The bridge current stabilizer is made on an operational amplifier. The voltage from the diagonal of the measuring bridge, proportional to the temperature, is amplified by a differential amplifier made on the operational amplifier; from its output, it is fed to the analog input of an analog-to-digital converter. A signal that carries information about the current temperature is presented at the output of the analog-to-digital converter in a form convenient for display with seven-element indicators. It arrives on a scoreboard consisting of three LED indicators and an LED.

The thermometer is powered by an AC voltage of 220 V through a transformer. To stabilize the bipolar supply voltage, parametric stabilizers are provided. The voltage for the current stabilizer is removed from the voltage divider on the resistors. The inputs of the reference voltage of the analog-to-digital converter are connected to the output from the resistors of the same voltage divider / Radio f I, 1985, p.

a temperature sensor, the adjacent arm of the first branch of the bridge has constant and variable resistors, the comparison arm opposite to the measuring arm is formed by a constant resistor, and the resistor adjacent to the measuring arm of the second branch of the bridge coincides with the essential features of the proposed device,

The device has a complex circuit.

The task to which the claimed utility model is directed is to increase the reliability of the device by simplifying the circuit. Another type of technical result, the use of which can be provided by the claimed utility model in comparison with the closest analogue, is to increase the measurement accuracy

To achieve the above technical result, the thermometer contains an analog-to-digital converter, a digital display unit, a power supply and a DC bridge, in the measuring arm of which there is a temperature sensor, in the adjacent arm of the first branch of the bridge - the first constant and first variable resistors are connected in series, and the conclusions the latter is connected to the inputs of the reference voltage of the analog-to-digital converter, the second constant resistor is opposite to the measuring arm of the comparison, and to the adjacent from eritelnym shoulder second branch of the bridge - a second variable resistor, wherein the feed diagonal of the bridge is connected to a common analog input terminal and a power supply napryazheSh I analog-digital converter, the analog inputs are connected to the measuring diagonal of the bridge.

Significant distinguishing features of the proposed device from the closest analogue are: the supply diagonal of the bridge is connected to a common analog output and voltage output of the power supply of the analog-to-digital converter, the analog inputs of the analog-to-digital converter are connected to the measuring diagonal of the bridge, the constant and variable resistors adjacent to the measuring arm of the first branch the bridge are connected in series, and the conclusions of the latter are connected to the inputs of the reference voltage of the analog-to-digital converter and hist adjacent to the measuring arm of the second branch of the bridge is made variable.

To enhance the technical result achieved, the digital ID block is made in the form of an ID-LCD indicator.

diagram of a thermometer with a shadcrystalline Ivdicatsrom as a digital display unit.

The thermometer contains an analog-to-digital converter I with a digital indication unit 2, a power supply 3 and a direct current bridge, into which the measuring transducer 4 is connected. The first variable resistor 5 and the first constant resistor b connected in series make up the connecting arm of the first branch 7 of the bridge. Conclusions the first variable resistor 5 is connected to the inputs of the reference voltage - L / on and + 1 / op analog-to-digital Converter I, the second constant resistor 8 is included in the opposite measuring arm compared to tions. Adjacent to the measuring arm of the second branch of the bridge 9 is formed by the second variable resistor 10,

The outputs of the power supply 3 are connected to the corresponding power inputs -f Up1 and -1 / p2 of the analog-to-digital converter I and the digital indication unit 2 The supply diagonal of the bridge is connected to the obscimal analog output 1 / o and the voltage output of the power source of the analog-to-digital converter I, Measuring the diagonal of the bridge is connected to the analog inputs -1 / in and -1 / in of the analog-to-digital converter I, Elok 2 of the digital display is connected to the information and sign-determining outputs of the analog-to-digital converter I.

As an analog-to-digital converter I, any push-pull analog-to-digital converter with automatic zero correction and determination of the input signal polarity can be used, for example, integrating K5721IB2 analog-to-digital converters implemented with LED indicators and K572PV5 designed for working with liquid crystal indicators in particular, I11 {KTs5-4 / 8 or IZHZ1-4 / 24A, Thermal sensor 4 is, for example, a commercially available resistance thermoconverter or npQbo o HJ Lu res op 11ostoyan1-she b and 8 and variable resistors 5 and 10 are selected resistance, the latter serving to balance the bridge at certain temperatures.

The thermometer is configured and operated as follows: After turning on the power supply 3, the thermometer is adjusted at two temperature points, for example, the temperature sensor 4 is placed in a two-phase water-ice system and, using the variable resistor 10, the zero reading is set on the display of the digital display unit 2, then the temperature sensor 4 is immersed in boiling water and by means of a variable resistor 5, a reading of 100 C is set,

For registering the thermometer, you can use the resistor store with precision resistors, including them instead of the temperature sensor 4.

When the temperature sensor 4 is placed in an environment whose temperature is to be measured, its resistance changes and takes a certain value, resulting in an imbalance of the bridge. The unbalance voltage is supplied to the input of the analog-to-digital converter I, which implements the push-pull integration algorithm, and the result of the error, which is the ratio of the voltage at the signal inputs to the voltage at the inputs of the reference voltage, is supplied to digital indication unit 2

When measuring temperature in a wide range, the current through the current-consuming constant resistor 6 changes slightly, but this does not affect the measurement results due to the inclusion of constant 6 and variable 5 resistors and termals: a. 4 in one branch of the bridge.

In addition, the scheme excludes the effect of changing the voltage of the power source and reducing the voltage of the internal source of the analog-to-digital converter under load on the measurement accuracy.

 5,

A # F, KWJPTW

Claims (2)

1. A thermometer containing an analog-to-digital converter, a digital display unit, a power supply and a direct current bridge, in the measuring arm of which a temperature sensor is included, in the adjacent arm of the first branch of the bridge - the first constant and first variable resistors, in the comparison arm, opposite to the measuring shoulder, the second constant resistor, and in adjacent to the measuring arm of the second branch of the bridge is a resistor, characterized in that the supply diagonal of the bridge is connected to a common analog output and voltage output of the power source an analog-to-digital converter, the analog inputs of which are connected to the measuring diagonal of the bridge, with the first constant and first variable resistors connected in series, and the terminals of the latter connected to the voltage inputs of the analog-to-digital converter, and the resistor adjacent to the measuring arm of the second branch of the bridge is made variable.  2. The thermometer according to claim 1, characterized in that the digital display unit is made in the form of a liquid crystal indicator.