SU111421A1 - Remote Ammonia Level Indicator - Google Patents

Description

In refrigeration technology, fluid meters are commonly used to indicate the level of ammonia, for example, circulating receivers. A disadvantage of such easy-to-use pointers is the presence of moving parts in them that reduce the reliability of the sensors.

In order to eliminate the marked deficiency B of the description of the invention, a thermometric bridge is used as a remote indicator of the level of liquid ammonia, the output voltage of which, after amplification in a two-stroke magnetic amplifier, is applied to a voltmeter whose scale has been calibrated by E magnitude of the height of the level.

Fig. 1 shows a schematic of a liquid ammonia level indicator gauge; in fig. 2 is an electrical diagram of the index.

The action of the gauge is based on the change in the electrical resistance of the conductor placed in the remote chamber, in which the level of liquid ammonia and the current heated is measured depending on the heat transfer medium.

Changes in heat transfer are caused by fluctuations in the level of the fluid and a change in the ratio of the lengths of the conductor — immersed in the fluid to that in the vapor space.

Since the heat transfer coefficient of liquid ammonia is greater than that of ammonia vapor, when the liquid level rises, the resistance of the heated conductor decreases, and as the liquid level decreases, the resistance increases.

The change in resistance D is greater, the greater the change in the level of the liquid. To eliminate the effect of temperature, the resistance of the conductor heated by the current is compared to the resistance of the conductor not heated by the current.

Practically, in the proposed device, platinum resistance thermometers are used as unheated and current-heated conductors.

No. 111421-2 -

Through the first kenagrevaemym thermometer resistance passes the usual current of 7-g8 ma, at which the temperature of the self-heating thermometer can be neglected.

In the second thermometer, on the contrary, the phenomenon of self-heating of the thermometer is used, for which a current of 3G-f 50 mA is passed through the thermometer, carrying out the required heating of the thermometer.

For measuring the height of the level, "cold IRg, IRg and" hot 2RT and 2Rj resistance thermometers are used, which are installed in the chamber / C, which serves to measure the height of the level, as indicated in FIG. one.

Both sets of thermometers to form a thermometric bridge are included in the branches of differential measurement circuits (Fig. 2).

Differential measurement circuits are powered from a common constant-current source with stabilized voltage.

Cold and hot resistance thermometers are connected to potentiometers / 7 and I in series with high impedance resistances (1000 ohms), in order to make the loop current / 2, / A almost independent of the resistance changes, 2RT, lRr to 2Rr.

With constant contour currents - ,, l, /, and h increments of the resistances A / and l.Rr, caused by fluctuations of the liquid level, are proportional to the conditional difference of the voltage losses across these resistances::

. .(one) . , (2;

To enhance the values of Af / and L Y, there is a push-pull magnetic amplifier consisting of two simple magnetic amplifiers with feedback MU and MU.

The control windings-potentiometers I and I-- of magnetic amplifiers MU and A4U, creating magnetizing amperages proportional to the members of expressions (I) and (2) {2Rr} and - (,; have n times

there are fewer turns than control windings I and G, which create a .multiples proportional to the members of expressions (I) and (2) / i () and / i () and are connected in the opposite direction to windings I, II and D, 1G.

As a result, the voltage at the outputs of the MU and MU amplifiers is proportional to the values of Af / and A (J- The voltage at the output of the differential magnetic amplifier is:

D (7 "d

A voltmeter G of the magneto-electric system complete with a phase-sensitive rectifier (the latter is not shown in Fig. 2) is intended to measure the difference in the voltages of Af / Yb unbalances. Voltmeter G is calibrated directly in the values of the level heights and has zero in the middle of the scale.

Differential measuring circuits balance the first one - when the iRr and 2Rr resistance thermometers are surrounded by ammonia vapor, and the second - when the iRr thermometers are surrounded by liquid.

In connection with this, the voltage deflecting the meter arrow of the instrument is as follows;

1) when the average level of the liquid is zero;

2) with increasing level (relative to the average mark) - proportional to the increment of resistance Dg, the increment of resistance of hypertension at this time is zero;

3) with a decrease in the level - proportional to the increment of the resistance of the AG, the increment of the resistance Ar at this time is zero.

If, instead of a measuring device, a polarized relay is connected to the output of the differential magnetic ssiliter (via a phase-sensitive rectifier), which turns on and off the solenoid valve through which the cooling fluid enters the refrigeration unit, then the described remote level indicator should be used as a three-position level regulator. the need for the device can be used microthermometers of resistance, with inertia 0.1-g 1.0 sec.

Subject invention

The use of a liquid ammonia as a remote level gauge of a known thermometric bridge, the output voltage of which, after amplification in a two-stroke magnetic amplifier, is applied to a voltmeter, with an offset scale value.

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