SU996925A1 - Conductometric device - Google Patents

Description

(54) ACCUMULATOR DEVICE

The invention relates to conductivity meters of electrically conductive liquid media, as well as devices for signaling the level or exceeding the limit of a given conductivity of the controlled medium and can be widely used, for example, in process control devices in the chemical industry.

Due to its simplicity and reliability in the work, self-generating devices for monitoring the conductivity of liquid media are widespread. Such devices are equipped with conductometric sensors included in the feedback circuit of amplifier generators. In them, the oscillating circuit enters the feedback circuit, as a rule, it transfers energy from the output to the input of the amplifier in a fixed ratio and ensures that the phase balance condition is fulfilled. The change of the transmission coefficient over the feedback circuit occurs due to the effect of the input quantity.

Known conductometric devices, for example, the control device 1.

The closest in technical essence to the present invention is a conductometric device, including an electrode conductometric primary transducer connected in series, an amplifier-generator with an oscillating circuit and a threshold device 2.

The known device consists of

10 amplifier generator with oscillatory circuit made on a ferrite toroidal core with connection windings, conductometric electrode primary converter and relay device. An inductive bridge is connected to the feedback circuit of the amplifier generator, one of the arms of which includes a conductometric electrode primary transducer.

The known device operates as follows. When the inductive feedback bridge is distributed in one direction, a negative feedback is generated25 and the oscillator is not excited; if the bridge is unbalanced in the other direction, the feedback becomes positive and the amplifier goes to

30 self-excited. The signal from the output of the amplifier generator arrives at the input of the threshold device, which forms the corresponding device side. The device triggering point is established by changing the other arm of the inductive bridge. The peculiarity in the conductometric device operation is the specificity of the periodic operation of the primary converter. In the autogeneration mode, an alternating current is applied to the measuring electrodes of the primary converter and a certain current flows through the converter, but if no current is generated, no current flows through the primary converter. At the boundary between the metal electrode of the primary transducer and the solution into which the electrode is immersed, an electric double layer is formed. This layer is caused by electric charges located on the metal and of opposite sign, which are in solution near the metal surface. The electric double layer in the first approximation is a flat capacitor. The complete replacement circuit of the converter can be represented as two series-connected capacitors and a resistance,. Therefore, to ensure the passage of current through this circuit, an alternating voltage is required. When powering. DC circuits of the converter electrode are polarized. In the no-autogeneration mode, on the one hand, no voltage is applied to the measuring electrodes and the current does not pass through the converter, and on the other hand, the amplifier-generator is not excited without positive feedback. But the known devices still work, which is explained by the presence of noise in the amplifier itself, which ultimately provides a conductive circuit between the measuring electrodes of the primary converter. Taking into account that the frequency and amplitude of noise signals can be very diverse, sleep and instability of the response point of known self-oscillating devices. This phenomenon is further aggravated when the electrolyte level is controlled. When the electrodes are periodically wetted, an oxide or other kind of film may form on their surface, which sometimes requires increased voltage for its breakdown. These phenomena narrow the sensitivity range of known autogenerating devices, significantly lower the accuracy class of autogenerator devices. The purpose of the invention is to expand the range of sensitivity of auto-generator devices. The goal is achieved by introducing into a known device, including an electrode primary transducer, an amplifier-generator with an oscillatory circuit and a threshold device, an additional generator of sinusoidal electrical oscillations with a frequency f greater than fmax and less than fmin / where fmc and fjT) ri are determined by the resonance characteristic the circuit of the resonant amplifier generator at a level not exceeding one-tenth of its maximum amplitude value, the output winding of the additional generator being inductively coupled on p. loop amplifier-generator. The drawing shows the proposed conductometric device. The device consists of an amplifier generator 1, made on a transistor and includes an oscillating circuit 2 with communication windings, an electrode primary converter 3, a threshold device 4 with an executive relay, an additional generator of sinusoidal electrical oscillations 5. The amplifier-generator 1 is equipped with an oscillatory circuit 2, ferrite core with windings and a contact primary converter 3. The output winding of the oscillating circuit 2 through the detector is connected to the input threshold 4. Threshold roystva device 4 generates actuating relay contact corresponding to the signal state of the controlled parameter. The output winding of the additional generator is inductively included in the oscillating circuit of the oscillator. The conductometric device operates as follows. The device is powered. An additional generator 5 starts operating, which, through communication with the oscillatory circuit, feeds the electrodes of the primary converter. Attached to the measuring electrodes, the voltage of the additional generator causes the passage through. With this current, which runs during operation all the time, the appearance of polarization phenomena in the near-electrode region of the primary converter is eliminated. When a predetermined value of conductivity between the electrodes of the primary converter is reached due to.

for example, a change in the conductivity of the monitored medium or a change in the level of its feedback between the output and the input of the amplifier generator becomes positive, and the generator amplifier switches to self-excitation. The signal from the communication winding of the amplifier-generator circuit is fed to the input of the threshold device. The threshold device is triggered and gives the appropriate signal.

In order that the signal of the additional generator could not cause false triggering of the threshold device through the path of the generator amplifier, the frequency of generation of the additional generator is chosen greater than the maximum frequency or less than the minimum frequency determined at a level not exceeding one-tenth of the maximum amplitude of the resonant characteristic of the amplifier-generator. with a maximum amplitude equal to the value of the voltage on the circuit during gassing. An additional generator must generate electrical oscillations of a sinusoidal current.

Compliance with these conditions ensures reliable operation of the device.

Thus, the use in the device of an additional generator with often more than the maximum or less than the minimum, determined at the level of one-tenth of the maximum magnitude of the amplitude of the resonant characteristics of the oscillating circuit

an amplifier generator and connected to an oscillating circuit, allows to obtain a device that extends the sensitivity range of the device.

Claims (2)

1. Leiman A.A. Self-generating magnetic transistor sensors and relays. M.,. Energie, 1971, pp.3-15. 2. Klimenko V.T. and others. Conductometric analyzers liquid sred.v sb. NIITEKHIM: Automation of chemical production, 1973, p.69-71 (prototype).