SU1485136A1 - Current stabilizing unit in measuring converters - Google Patents

Abstract

The invention relates to a circuit arrangement for stabilising currents and amplifying voltages in measurement converters used in metrology and automation technology. Using this circuit arrangement, all electrical sensor output signals - currents, voltages, resistances - can be converted and amplified into a common electrical signal. The aim of the invention is to achieve an improvement in the technical parameters while at the same time reducing the use of components, and to reduce markedly the production effort. The present invention is based on the object of making it possible to construct a miniaturised measurement converter, achieving a higher reliability, additionally minimising heating which is dependent on the drive level, and of supplying the 4 mA basic current into the measurement circuit without current losses. The essence of the invention is that a double power source having a common base point supplies a balanced circuit consisting of two transistors, one of the transistors having a base-collector short and the emitter of the said transistors supplying a second balanced circuit consisting of two further transistors, and on the opposite side of the one transistor, the other transistor having a base-connector short, and the two emitters of the other two transistors being connected to a measurement-range circuit. An output stage supplies into this measurement-range circuit a ... Original abstract incomplete. <IMAGE>

Description

The invention relates to electrical engineering and is intended to convert electrical signals into a unified signal and further

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^ gain. The purpose of the invention is to improve the accuracy of the device. The measured and balancing signals are fed to the emitters of the transistors of differential amplifiers loaded with a dual current source. In this case, the balancing signal, which is simultaneously the unified output signal of the device, is produced by a special output stage. Combining the measuring normalizing transducer into a single unit with electrical signal sensors makes it possible to abandon the use of special complex schemes for connecting measuring channels, proceed to processing a unified signal and simplify group measuring transducers. 2 hp ff, 2 ill.

The invention relates to electrical engineering and can be used to convert electrical signals into a unified signal and further amplify it.

A known circuit for stabilizing currents in measuring transducers with a medium voltage forming unit, in which it is not possible to amplify the signals of operational amplifiers (GDR patent No. 159279, class C 01 K 17/02, 1975)

A similar scheme is known that has a low temperature stability (GDR patent No. 135303, cl. C 01 K 17/02, 1970).

The purpose of the invention is to improve the accuracy of the stabilization unit.

Figure 1 shows the functional diagram of the block stabilization currents in

measuring transducers; figure 2 - schematic diagram of the node from the measuring range.

The stabilization unit (Fig. 1) contains a dual current source 1, the main and additional differential amplifiers, the first of which is built on transistors 2 and 3, the second on transistors 4 and 5, while transistors 3 and 4 are connected according to the diode principle to the bases of transistors 2 and 5, respectively. The stabilization unit also contains a node 6 of the measuring range with two branches, one of which includes the measuring resistor 7, and the other - the compensation resistor 8 and the source 9 of the compensation signal, the output of which is connected to one of the resistive outputs 1485136

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four

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torus 8, the other-output of which is connected through the mode resistor 10 to the output terminal and to another output of the resistor 7.

The emitter of transistor 2 (figure 2) is connected to the collector of transistor 4 through serially connected its resistance 11 transmission line and measuring resistor 7. th

The unit stabilization currents in the measuring transducers works as follows.

The beginning of the measuring range is determined by the compensation resistor 8. When the resistance of the measuring resistor 7 increases, the potential at the collector of transistor 5 decreases, as a result of which the potential at the collector of transistor 3 increases. Due to the dual current source 1, the transistors are loaded with high-impedance dynamic collector resistances, thanks to this, high ratios are achieved 25

voltage amplification. “Source 9 produces a current that creates a voltage drop across resistor 10, equivalent to the product of the change in resistance-resistor 7 and source current! 30 A uniform current signal is generated at the output of the device.

The use of two current-controlled differential amplifiers serves for temperature compensation of the base currents and voltages at the base-emitter junctions.

The change in the potential at the emitter of transistor 4 can also be achieved by a fixed resistor 7, and in 40 this case, the currents can be converted into a unified current signal,

In the same way, a change in the potential at the emitter of transistor 4 can be achieved by applying a voltage in series with a fixed resistor 1, as a result of which the voltage can also be converted into a unified current signal.

In addition, if a constant resistor 7 is installed and the voltage source is switched on between the bases of transistors 4 and 5, causing the formation of a compensation current through a change in the base potential of the transistor 5, a uniform choke signal is also formed according to the described principle. Subject to specified36

principle, specifically for processing measuring resistors using a 4-wire switching circuit or remote sensors (FIG. 2), it is possible to switch on the measuring resistor 7 to a differential amplifier with current control of transistors 4 and 5 through the resistance of 11 transmission lines.

With identical transistors 2-5 through the resistance of 11 transmission lines flow only reduced by the current gain of the transistors currents, the impact of which is compensated and does not cause measurement errors.

The resistance of the 11th transmission line in the emitter circuit of transistor 2 is compensated by the voltage gain of transistor 5,.

The resistance of the 11th transmission line in the collector circuit of transistor 4 is also compensated by the voltage gain of transistor 4.

The useful effect of the invention lies in the fact that it is possible to carry out a seamless integration of the circuit, as a result of which measuring transducers with minimal dimensions and miniaturized volume can be built. This has achieved a basis for a constructive association of measuring sensors and measuring transducers. ”A measuring transducer can be built into the compartment for connecting a measuring sensor, such as a resistance thermometer. This creates a measuring sensor with a unified output signal.

In addition, for measuring sensors with a unified output signal, there is no need for laying special wires, which is required, for example, for resistance thermometers or umopar, and all the advantages of transmitting a unified signal can be used.

The proposed design of the measuring transducer has a positive effect. on the cost of the measuring point,

By means of the invention, an increase in reliability is achieved.

In addition, the sensor and the measuring transducer can be combined into a single unit, with the definition5 1485136

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Lenght junction in automation devices is only a unified signal, as a result of which the electronic part can be customized by the instrument manufacturer to many hitherto unused sensing elements characterized by technologically justified large tolerances. This should take into account the significant savings on platinum resistance thermometers, replaced by semiconductor elements.

The embodiment according to the invention provides a variety of applications. All used for automation, in particular for temperature measuring equipment, measuring sensors can be connected.

Claims (3)

Claim 1. Current stabilization unit in measuring transducers, which contains a dual current source, a main differential amplifier with current control (position 2.3), a measuring range node with two branches, one branch of which includes a measuring resistor, and the other - a compensation resistor , and the source of the compensation signal (position 9), the output of which is connected to one of the terminals of the compensation resistor, the main differential amplifier consists of two transistors of the same type, one of which is connected principle of the diode to the base of another transistor tlichayuschiysya about the fact that, in order to increase accuracy, the dual current source outputs are connected to the collectors of the transistors of the main differential amplifier, the emitters of which through the introduced additional similar differential amplifier with current control (positions 4,5) connected to branches The node of the measuring range, in addition, the control input of the compensation signal source is connected to the collector of the transistor of the main differential amplifier, and a mode resistor (position 10) connected in series with a compensation resistor and a free output connected to the emitter of the transistor is connected to the node of the transistor. 20 additional differential amplifier. 2. Block pop. 1, which differs from the fact that the emitter of the transistor of the main differential amplifier through the collector-emitter? The transistor circuit in the diode switching on of an additional differential amplifier is connected to one of the terminals of the measuring resistor, 30 other terminal of which is connected to the free output of the modulating resistor and to the output terminal. 3. Block pop.1, imitating 35 that the emitter of the transistor of the main differential amplifier through the measuring resistor and their resistance transmission lines are connected by a four-wire circuit with ₄₀ collector transistor in the diode switching on additional differential amplifier. srig.1 2