SU1735753A1 - Humidity meter - Google Patents

Abstract

Usage: moisture measurement of bulk and fibrous materials. SUMMARY OF THE INVENTION: the device contains a voltage divider formed by an exemplary resistance and a primary converter, a variable voltage source, controlled. scale converter, comparator, integrator, amplitude detectors, recorder „3 sludge

Description

The invention relates to the measurement of electrical quantities and can be used to measure the relative humidity of various substances by the conductometric method.

A number of direct metering moisture meters are directly estimated, based on the inclusion of a primary converter in one of the arms of a bridge circuit or a voltage divider type circuit.

Their main disadvantage is the narrow working range due to the shunting effect from the input circuits of the recording instrument in the zone of low humidity values. The closest technical solution to the proposed is a device containing an alternating voltage source connected to a series-connected primary converter and to an exemplary resistor, the junction point of which is connected to the measuring

a circuit including a voltage divider, a phase shifter, two pulse drivers, a phase comparison unit, a low-pass filter, an amplifier, a gain maximum transmission unit, a harmonic sampler, a reversible counter, and a digital indicator.

This device also has a narrow operating range due to the large uncertainty of results in the zone of low humidity values, since its measuring circuit is connected directly to the outputs of the primary converter and the sample element, shunt their resistance „

The purpose of the invention is to expand the operating range of a known instrument by eliminating the connection of the recording instrument to the output of the measuring circuit.

The goal is achieved by the fact that the device containing

have eaten m

: l

W

A voltage source, a primary converter, one of the terminals of which is connected to the common bus and the other to the output of the reference resistor, and a recorder, have introduced an adjustable scale converter, a voltage comparator and an integrator, with the information input of the adjustable scale converter along with one of the inputs the recorder and the inverting input of the voltage comparator are connected to the output of the source; the control input of the adjustable scale converter is connected via an integrator to the output omparatora voltages straight input of which is connected to the second terminal of the primary transducer regulirueKoeffitsient transmit output latter depends on the voltage U zatvomogo soe- scale converter 20 D, since R, (U4), the

Dinen with the input of the reference resistor and the second input of the recorder. In addition, two amplitude detectors, the inputs of which are connected to the outputs of the source and the second terminal of the primary converter, are also introduced into the known device, and the outputs of the detectors are connected to the inputs of a voltage comparator, while the adjustable scale converter is designed as an amplifier with adjustable gain,

{fa fig. 1 shows a structural diagram of the meter (Fig, 1); in fig. 2 - time diagram of the work of its main nodes; Fig. 3 is a schematic diagram of one of the options for implementing an adjustable large-scale converters.

The moisture meter contains a constant (or alternating) voltage source 1, an amplitude detector 2 (designed to rectify an alternating voltage according to the amplitude level or to transmit a constant

4ST

R,

 min at U

to "/ and O and K (U /"

25

And + R1

 max at U 5- U 4 The meter works as follows:

At the time of start-up (corresponds to the moment of switching on the source 1 in Fig. T and t 0 in Fig. 2) the integrator C is 30 times, t e, 1 0 and the transfer coefficient of the adjustable scale converter 5 is 1, i.e. Q 1 (carried out by the selection of resistors 11 and 13 in FIG 3, in accordance with

35

condition KRJЈ All-. R "

one

As a result, after switching on the device, the measuring circuit 7 first 40 receives the voltage U4 (corresponds to the segment O-t in Fig. 2),

Two voltages are applied to the comparator 3 for comparison: U. K4Uf and

lba K5K7K.0Ut, where K2 and coefficient FIV / I V / OPA GTL JKI JLU Л 4 ЦГ - ААаЧП f I Wt- I J г L

hours / transmitters of detectors 2 and 10,

of the voltage), the comparator 3 (node "5 hours,„ „Azh

„| K7 Ro / (RA + Ro) voltage over-comparison ratio, integrator h, e / ohc,

“A fchi measuring circuit 7, Because

adjustable scale converter 5 (designed to amplify the input signal) and recorder 6 (millivoltmeter) ,. Measuring circuit 7 is made up of resistance 8 of an exemplary constant resistor (Rg) and resistance 9 of primary converter (RA). Amplitude detector 10 performs the same function as (Hector 2. Notations adopted in Fig. 2: W is relative humidity controlled material; And,, U3, U4, V $ are the voltages from the outputs of the same name U const, K0-1, where Kf is the transfer coefficient of the large-scale conversion - 50 bodies, K2 and K7Ј 1, then U, 0 u and the comparator 3 voltages in time t1 produces a pulse signal ul O (line 1 in Fig. 2) in

Its effect on the integrator C will be expressed by the appearance at the input and supply to the control input of an adjustable scale converter 5 of linearly increasing voltage and. (line 2 in Fig. 2), The latter will cause with mo5 $

start points t 4, .. - moments

NUH nodes; t, tg are measurement cycles; t-, its termination; tHVW is the duration of the measurement cycle; the duration of the recovery period or return to is-. driving condition. K, K4, Kg - transfer coefficients of like nodes and Converter 5 (FIG. 3) are executed on resistors T1, 12. 13 with resistances RH, RO, respectively, and operational amplifier I. Drain-source of field-effect transistor 15 with resistance, R, g serves as a variable resistance and forms with the resistor 11 an adjustable voltage divider

The transfer coefficient of the latter depends on the voltage U on the gate, since R, (U4),

R

4ST

R,

 min at U

to "/ and O and K (U /"

five

And + R1

 max at U 5- U 4 The meter works as follows:

At the time of start-up (corresponds to the moment of switching on the source 1 in Fig. T and t 0 in Fig. 2), the integrator C is open, t, e, 1 0 and the transfer coefficient of the adjustable large-scale converter 5 is 1, i.e. Q 1 (carried out by the selection of resistors 11 and 13 in FIG 3, in accordance with

condition KRJЈ All-. R "

one

As a result, after switching on the device, the measuring circuit 7 first receives the voltage U4 (corresponds to the segment О-t in Fig. 2),

Two voltages are applied to the comparator 3 for comparison: U. K4Uf and

U const, K0- 1, where K-f is the transfer coefficient of the scale converter, K2 and K7Ј 1, then U, 0 ig and the voltage comparator 3 at the time t1 produces a pulse signal ul О (line 1 in Fig. 2) in

Its effect on the integrator C will be expressed by the appearance at the input and supply to the control input of an adjustable scale converter 5 of linearly increasing voltage and. (line 2 in fig. 2), the latter will cause

ment t4 is an increase in the coefficient K, the transmission of the adjustable scale converter, due to the growth resistance of the drain-source junction transition of the field-effect transistor 15 in FIG. 3 and an increase in the input voltage of the amplifier And o

As a result, an ever-increasing alternating voltage will be applied to the measuring circuit 7 from the time t.

and

5 KrUf. Where. (line 3 in fig „3). The consequence of this is that the voltage U increases and the voltage proportional to it, When the ratio Uz U10 is reached, the voltage increases of the measuring circuit 7, i.e. U, will stop (reflected by the time t2 in Fig. 2), and as the comparator 3 generates a signal of the opposite level. Thanks to the discharge of the integrator k that started at the same time, after some time (interval t, figure 2) the voltage regulation process on the input, the circuit 7 resumes again, but at the time t also ceases. As a result of this interaction, the nodes 3 and 5, which form an astatic tracking autoregulation system, at the input of the converter 5, a sufficiently fast voltage

Novits almost

Uy K 5- U ...

Its value (or amplitude) can be found by substituting the value Ku, determined from the condition: U

"U" - KfK7U, Oh,

It is easy to see that with K2

   1 we have

“; - Sjifi,

This recorder is connected as shown in FIG. 1, will be under a voltage equal to the voltage difference (and and U4, and its arrow deflects by an angle equal to tf $

 v tt d o

- V, R.

where K6 - registrar transfer coefficient 6.

| Formula

Taking into account the fact that it was obtained outside the measuring circuit, namely, at points with higher energy possibilities, it can be concluded that the shunt effect from the input circuits of the recorder is reduced to the result of the evaluation.

Receiving a signal about the humidity of the material being monitored outside the measuring circuit 7 makes it more stable, reduces the level of interference when operating in the region of small values of W,

As a result, a significant (3 times) reduction in the lower limit of measurements and expansion of the operating range are achieved.

20 | Formula

and

et e and

25

h oh b

to

Moisture meter containing

the alternating voltage source, the primary transformer, the exemplary resistor, the recorder, the exemplary resistor and the primary converter being connected in series, characterized in that, in order to extend the measurement range to low humidity,

30 | it additionally contains an adjustable scale converter, a voltage comparator, an integrator, two amplitude detectors, and the information input of the adjustable scale converter, one of the recorder inputs and the input of the first amplitude detector are connected to the alternating voltage source detector connected to

JQ is the first input of a voltage comparator, the control input of the adjustable variable converter is connected via an integrator to the output of a voltage comparator, the second input of which is connected through the second amplitude detector to the primary converter, which is connected to the reference resistor and the second recorder input.

35

4S

Claims (1)

Formula of the invention A moisture meter containing an AC voltage source, a primary converter, a reference resistor, a recorder, the reference resistor and the primary converter being connected in series, characterized in that · in order to expand the measurement range to a region of low humidity values, [it is additionally contains an adjustable scale converter, a voltage comparator, an integrator, two amplitude detectors, and the information input of an adjustable scale converter, about one of the inputs of the recorder and the input of the first amplitude detector are connected to an AC voltage source, the output of the first amplitude detector is connected to the first input of the voltage comparator, the control input of the adjustable scale converter is connected through the integrator to the output of the voltage comparator, the second input of which is connected through the second amplitude detector to the primary converter , the output of the scale converter is connected to the model resistor and the second input of the recorder. FIG. 3