SU1739203A1 - Electromagnetic flow rate converter - Google Patents

Description

x | WITH

The invention relates to instrument engineering, in particular, to electromagnetic transducers for the flow of liquids, and can be used in systems for monitoring and controlling the flow of electromagnetic fluids in industrial technological processes, in systems for metering water consumption in public utilities, and the like.

The purpose of the invention is to improve the accuracy of the conversion.

Figure 1 shows the block diagram of the device; Fig. 2 shows timing diagrams explaining the principle of operation of the device.

The electromagnetic flow transducer (Fig. 1) contains a primary transducer 1, which includes inductor 2 and electrodes 3 and 4. Inductor 2 is connected via a resistor 5 to the output of inductor power supply 6. Electrodes 3 and 4 are connected to the input of the amplifier 7, and a resistor 5 is connected to the input of the amplifier 8. The outputs of the keys 10-13 are connected to the input of the integrator 9. The inputs of the keys 10 and 13 are connected, respectively, to the outputs of the amplifiers 7.8, and the inputs of the keys 11, 12, respectively, to the outputs of the source 14 of the positive reference voltage and the source 15 of the negative reference voltage. A comparator input 16 is connected to the output of the integrator 9, the output of which is connected to the information input of the control unit 17. The first, second, third and fourth outputs of the control unit 17 are connected respectively to the control inputs of the keys 10, 13, 11 and 12, and the fifth and sixth outputs to the first and second inputs of the inductor power supply 6. The device also contains a reference frequency generator 16, the first input of which is connected to the counting input of the pulse counter 19, and the second output to the counting inputs of the programmable frequency divider 20 and the programmable one-vibrator 21. The information output of the pulse counter 19 is connected to the information inputs of the programmable divider 20 and programmable one-shot 21, and information output of a programmable divider 20 to the start input of a programmable one-shot 21, Seventh, eighth, ninth and tenth outputs of control unit 17 By connecting respectively to input initial setting and entry authorization counter 19 counting pulses entry overwriting of the programmable divider 20 and the entry overwritten programmable monostable 21. The output monostable 21 is connected to a programmable input of the stabilizer 22 with pulse amplitude output

which is connected to the input of the filter 23 of the lower frequencies.

The device works as follows.

The control block 17 outputs

V and VI clocking pulses with a frequency that is a multiple of the frequency of the mains supply, coming to the first and second inputs of the inductor power supply unit 6, time diagram

clock pulses (U ™) is shown in figure 2a. The inductor power supply unit 6 forms, in accordance with the clock pulses, symmetric bipolar pulses supplied through the resistor 5 to

inductor 2 of the primary converter 1. The timing diagram of the power pulses of the inductor (ip) is shown in Fig. 2b.

The signal from the electrodes 3 and 4 of the primary converter 1, which occurs when the excitation current passes through the inductor 2, is amplified by the amplifier 6 and through the switch 10 controlled from the output 1 of the control unit 17, is supplied in the measurement cycle of the output signal to the input of the integrator 9. The signal c

the resistor 5, proportional to the excitation current, is amplified by the amplifier 8 and through the key 13, controlled from the output 11 of the control unit 17, is fed to the input of the integrator 9 in the reference signal measuring cycle. The key control signals 10 and 13 are formed in such a way that first the integrator 9, an amplified signal from electrodes 3 and 4 is applied at positive and negative fields of the excitation current

the inductor, and then the amplified signal from the resistor 5, also at two fields of the excitation current, the keys 10 and 13 are in the closed state for a time interval multiple of the power supply frequency,

in which the current in the inductor reaches a steady state. Timing diagrams of the key management signals 10 and 13 (Ui, Un) are shown in Fig. 2c and d.

In the measurement cycle of the signal from the EDDOR, when the key 10 is in the closed position, the capacitor of the integrator 9 is charged with a signal proportional to the signal from the electrodes. At the end of the charge, the key 10 opens and closes.

a key 11 or 12 connecting the input voltage of the integrator 9 to the discharge voltage, respectively, from the source 14 of the positive reference voltage or from the source 15 of the negative reference voltage in

depending on the polarity of the inductor's power pulse. The keys 11 and 12 are controlled from the outputs III and IV of the control block 17, respectively. Timing diagrams of key management signals 11 and 12 (Uui, Uiv)

shown in Fig.2d and e, respectively.

Simultaneously with the connection of the discharge voltage, the counter resolution input of the pulse counter 19 from the output VIII of the control unit 17 is given the counting permission signal and the counting of pulses to the counting input from the first output of the reference frequency generator 18 begins. When the voltage on the integrator 9 passes through zero, the comparator 16 is triggered and the passage of the reference frequency pulses to the pulse counter 19 is prohibited. Timing diagrams of the signals at the outputs of the integrator 9 (1) and) and the comparator 16 (UK) is shown in fig.2zh and h.

The number of pulses recorded in the counter 19 pulses during the discharge when the signal is measured with one polarity of the inductor's power pulse is stored in the counter 19 and is added to the number of pulses fed to the counter 10 when the capacitor of the integrator 9 discharges with the other polarity of the power pulse inductor. Then the contents of the pulse counter 19 are overwritten by the information input to the program- ming: one uniqualor 21 rewriting signals, which are available at the rewrite input of the program- ming one-oscillator 21 from the output X -.17 of the control, and the rewriting is done by the initial setting of the counter 19 at the input of the initial setting with output VII control block 17. A similar -G groove converts the sig. from resistor 5 in the measurement of the signal supports when the key 13 is closed, with a total .c with i / pulses recorded in the counter 19 when the integrator 9 is discharged during the positive and negative polarity of the inductor power pulses , is rewritten by the informational input to the programmable divider 20 of the rewriting signals received at the rewrite input of the programmable divider 20 from the output IX of the control unit 17. Timing diagrams of the counting resolution signal, rewriting signals and the initial setup signal at outputs VIII, X, IX, VII of the control unit 17 are shown in Fig. 2m. and, k, l respectively.

The total number of pulses NI recorded in the counter 19 in the measurement cycle of the signal from the electrodes at both fields of the inductor supply pulses is defined by the following formula:

uЈ + and "

iet

where Ti is the integration time;

FI is the frequency of the counting pulses at the first output of the reference frequency generator 18;

UBX + and IVH - signal from electrodes with positive and negative fields of the inductor supply pulse;

Wet - reference voltage.

Similarly, the total number 2 is determined when measuring the reference signal.

 Fi

U + UOT

U:

at

where Uon +, Uon is the reference signal at the positive and negative fields of the inductor's power pulse.

The counting input of the programmable divider 20 continuously receives counting pulses from the second output of the reference frequency generator 18, which reads the written information down to zero. Therefore, at the output of the programmable divider 20, a sequence of pulses is formed, the period of which is proportional to the reference signal. The pulse sequence from the output of the programmable splitter 20 is fed to the start input of the programmable one-shot 21, the counting input of which is also fed to the pulses from the second output of the reference frequency generator 18, which reads the recorded information to zero. Thus, at the information output of the programmable one-shot 21, a pulse-width signal is formed, the follow-up period of which is proportional to the seat from the reference resistor 5, and the duration to the signal from electrodes 3 and 4,

The pulse width period T and the duration are determined, respectively, by the following formulas:

T n2

15 20 25 25 30 35 40

45

five

where F2 is the frequency of the counting pulses at the second output of the reference frequency generator 18. The pulse width signal from the information output of the programmable one-shot 21 is fed to the input of the pulse amplitude stabilizer 22, from which the amplitude-stabilized pulse-width signal goes to the low-pass filter 23, which converts this signal to an analog output signal (voltage or current).

The formula for converting a pulse-width signal in the case of conversion to a voltage U vyh is

UBWX - UCT Y UCT -

UBt + U

Bx

Uon b uon

where UCT is the stabilization voltage.

This device improves the accuracy of the flow conversion, since the output analog signal, as follows from expression (1), does not depend on the constant time of the integrator, which eliminates the effect of instability of the integrating circuit on the measurement accuracy.

Claims (1)

The invention Electromagnetic flow converter containing a primary converter whose inductor is connected via a resistor to the output of the inductor power supply and electrodes to the input of the first amplifier, the output connected through the first key connected in series, the integrator and the comparator to the information input of the control unit, the first, the second, third and fourth outputs of which are connected respectively to the control inputs of the first, second, third and fourth keys, the fifth and sixth outputs of the plug The first and second control inputs of the inductor power supply, respectively, and the seventh and eighth outputs, respectively, to the initial setup input and the pulse counter counting enable input, the counting input connected to the first output of the reference frequency generator, the second amplifier, the input connected to the resistor, and the output - to the entrance the second key, the source of the positive reference voltage, connected by the output to the input of the third key, the source of the negative reference voltage, - connected by the output to the input of the fourth key, differing in the fact that, in order to improve the accuracy of the conversion, a programmable frequency divider, a programmable one-shot, serially connected pulse amplitude stabilizer and low-pass filter are entered, the outputs of the second, third and fourth keys are combined and connected to the input of the integrator, counting PU programmable frequency divider and the programmable one-shot is connected to the second output of the reference frequency generator, the overwriting inputs are respectively to the ninth and tenth outputs of the control unit, and the information inputs are connected to the information input of the pulse counter, the start input of the programmable one-shot is connected to the output of the programmable frequency divider, and the output is connected to the input amplitude stabilizer pulses. V UK V. v. III I I I I I V. v. V  I I I I