DD210354A1 - CIRCUIT FOR MEASURING THE PERIOD OF DURATION AND FREQUENCY - Google Patents

Abstract

The invention relates to a circuit for analog measurement of the period or the frequency of an AC voltage. The aim of the invention is to provide a circuit which has a low component requirement for carrying out the measurement with high measurement accuracy and in particular no Glaettung needed. The solution is that the circuit has a Saegezahngenerator with zeroing back and supplies via voltage follower, storage capacitors, diodes and a Endspannungsfolger a proportional to the period or d.Frequenz voltage. The Anw.der invention is given in particular in synchronous generators whose voltage frequency is to be controlled proportionally.

Description

a) Title of the ax indang

Circuit for measuring the period and frequency

b) Field of application of the invention

   The invention relates to a circuit for analog measurement of the period or the frequency of We cha elsp annungeii, wherein these are converted into a proportional DC voltage value, which can be used in control loops as actual or desired value.

c) 'Characteristic of the known technical solutions.

Circuitry for converting the period or the frequency into a proportional

-. nale DC voltage known in which of the

'15 formed periodically controlled Reciiteckspannungen

will.n ,,, .-, whose mean value represents - .. Mafiv: ' _i for ⁱ -'di.e> .Fr $ qu.enz · or period.

Also known are circuit arrangements in which the time-linear increase in the voltage of a

Sawtooth generator or integrator during one

Period is used to determine the period or frequency by also averaging.-the · required averaging-out of rectangle

25 ... ^{0 (i} f ^r delta voltages requires the use of

Filters (low pass) whose tent constants are detrimental to the use of the arrays in control loops.

Thus, from DS-OS 2 254 363 a method for measuring frequency and pulse duration is known, the

an averaging of several periods or pulses allowed and sawtooth generators, ρ a flip-flop switching stage and a comparator stage

consists *

10 14 & ^e z DE-OS 2 720 023 is a circuit for measuring

- ^; , the reciprocal frequency of an AC voltage.

- who works with rectangular or sawtooth • output signals, a frequency converter, holding amplifier, counting circuit, number memory and a digital-to-analog converter has.

Furthermore, from DS-OS 2 942 705 a method and circuit for frequency measurement is known, in which the measured alternating voltage frequency is compared with a frequency of a -Saktoszillators, a Synchronisieirer and a · frequency divider, ^ obei the

Frequency divider and the synchronizer designed as an integrator digital-to-analog converter.

"* ~ \ control and the output terminals of the converter

_y '·

Deliver measuring voltage.

25 · feiter v is ^from DD-WP 89 '912 a. switching

Arrangement for analog frequency measurement, in which the zu.messende frequency is modulated with an accurate frequency grid and the difference frequency is screened out and 'a discriminator on '.

feeds a threshold switch.

d) Object of the invention

The aim of the invention iat the creation of a circuit for determining the period and 'from the frequency of an AC voltage with little effort and high accuracy.

e) Presentation of the> wesena dar invention

The invention has for its object to find a circuit for determining the period and from it the frequency, one of the period.

Proportional output.3Sdelta results in "£ .r .- = -

no averaging is required. According to the invention, this object is achieved in that in the measurement of the period, the output SDannung.Sägezahngenerators two Spannungsfolgef "on two Speicherkönde'naätbreh

of which one is discharged when the passage is positive and the other when the passage is negative, and the output voltage is supplied via two diodes to a voltage follower whose output is connected to the output resistance

connected is.

In the. Scarf device for measuring the frequency using the circuit arrangement for measuring the period is the maximum occurring at the end of each half-cycle 25- of the AC voltage

Sawtooth voltage, which appears via the voltage follower at the output resistance, with a controller durch.Verstellung the slope steepness of the sawtooth voltage to a constant value,

In this case, one of these steepness steepness proportional voltage value is used as a frequency-proportional output value.

The voltage of the sawtooth generator increases linearly in every half cycle up to a maximum

> worth U. _m ^ to which of the period duration oro-

is proportional and at each lulldurchgang the

AC voltage tilts back to Hull. Inventions\     , * ..

According to the output voltage, the. Sägezahngenerators U _{Λ is given} by voltage follower on two storage capacitors whose discharge takes place once in each period by 180 ° out of phase. On; One capacitor thus appears to have a voltage gradient that corresponds to the voltage curve of the sawtooth generator between 0 ° and 180 °

and maintains between 180 ° and 360 ° the achieved voltage value.

On the other capacitor appears the. Tension of the _: sawtooth generator between 180 ° and 360 °, while, between -0 ° and. 180 ° the voltage value

remains constant.

The outputs of the storage capacitors are each fed via a diode to a further voltage follower, at the output of which only the respectively greater voltage of the safety capacitors; appears and

so that a DC voltage without ripple, which is proportional to the period, ΐ scored,

This voltage is compared with a nominal value when measuring the frequency and the difference controls the charging current U _Q via an amplifier. of the saw

tooth generator so that agreement with the setpoint is achieved. The required value of the charging current of the sawtooth generator is

proportional to the following relationships of frequency:

d ü " _Λ υ"

Charging current I ₀₁ = C ₁ · = * C ·. Si SAES

- ^G 1 ^J c1

^U c1 max ^{= ü} target

f) exemplary embodiment

The invention will be described below in an execution. example closer _v ;. _? explained _{; i>} -iverden :. The. Associated with this, "ζβίφ" eliisa Ssehai ^ ung ,,; bgo. ,, w ^ iche ^ - de. _: te-sawtooth generator is formed by the capacitor G 1,

This is charged by the constant current control circuit juit dexa 'Iransiator 7 1 brT constant current, where Y 1 is the difference between the actual residual current at the resistor R 1 and the current at the reactor Y 6 or the Zener diode Z 1 upcoming

Konatantstrom setpoint is controlled *. By the constant charging current linear with the

Time increasing voltage U _Λ mrd the bases of

egg

 Transistors V 2 and 7 3 supplied. The transistors. are connected as a voltage follower and transmitted

the voltage increase across the capacitor GT on the capacitors C 2 and G 3.

The capacitors G 1, G 2 and G 3 are subjected to the full passage of the input alternating voltage U _w

through, the transistors 7 7, 7 8 and 7 9 discharged. The control of the discharge takes place in such a way that C 1. · Is discharged at every IJulldurchgang, C. 2 only at the positive Hulldurchgang and C 3 only at the negative Hulldurchgang · The required impulses at the

Transistors 7 7 »V 8 and 7 9 are effected by the capacitors G 4 and G 5, which carry current during the rise of the AC voltage from Hull to the Z voltage at the Z diodes JO Z 3 and Z 4 «.

/. The assignment of the corresponding euildurchgänge

takes place through the diodes D 3 to D 8.

Through the diodes. D 1 and D 2 are each the larger of the 'lying at the: capacitors G 2 or G 3' voltages to the base des'als _t voltage follower gea chatteten transistor 7 4th

led, there, the; greater. Voltage: the diode 'blocks, and the' lower voltage 'is applied.

There. the capacitors G 2 and G 3 are discharged only at every second zero crossing, only becomes

in one half-period the voltage rise at the capacitor G 1 is taken over during the other ~). Half-period remains the maximum voltage reached

obtained at the condenser G .1. By the umv 180 staggered: discharge of G 2 or G 3

appears at transistor 7 4 or »at the output -

resistance; R ^: 2 only -the voltage; U ... ei max

Is used as setpoint for the constant charging current -U ₀ ^ - on Tranais tor 7 1 only the Z-Sp annung on the Zener diode Z 1, then the output voltage

U ₄₁ on 'R. 2:

i '- ^U 21 -C · ^{o1 Üg} 1

¹ G 1- τη ¹ "1

ÜA1 = u _R2 = u _{c1 max} = WTTö-T · 4

d. H. proportional to the period T of the AC voltage ·

To measure the frequency f = - ^ is by a 'control loop, the voltage. u * _ = v'U. by

'Adjustment of the charging current i .. on a kon

fixed constant value *

_: j . In the example, this is done by means of

equal to the voltage Uv, ₂ with the Zener diode Z 2.

The, difference is ver over the transistor 7 5 ver

strengthens the - 2ransi3tör, 7 6 controls, wi

..the setpoint for, .den, constant current i and. at the same time, the. Aasgahga voltage U _? It is, it is.

^U A 2

^{At ü} c1 mas- = ^U z 2 results

U,

ο 1 - ΗΊ ^ ^w '- "0" 75 "VTjT

That is, the output voltage. ü ₍ , ^ ^ ³ "^ proportional to the frequency.

The effect of the controlled system is as follows; When the voltage U ^. _? is greater than the voltage IT _o , vl / ird the transistor 7 5 and thus'. ..the transistor 7 6 turned on and thus

; , % 6 ^{s Ü} A 2 = ¹ CT. · * -. *

also smaller. This will be the constant current

ί ₀ 1 ^{Mie U} o Uax =% 2 is also smaller and Ur ₃ ο = 'ü "ο is reached again.

To the. Compensation of the dead time at the change of '5 U. from one half-period to another

the Regelicreiatransistoren: Y 5 and Y 6 still with _ä . control technology. Correction elements beschältet who

the: which are not shown in the application example. '.

Claims (2)

3rfindungsana pr uch j 1. Circuit arrangement for measuring the period duration of an AC voltage using a sawtooth generator and resetting the The same at zero at each UuIdurengang the AC voltage, characterized in that the output voltage of the sawtooth generator ^ - on the capacitor (C 1) via one voltage w ^J _- follower (V 2, V 3) on two Speicherkondenaa- 10. gates (C 2, C 3) is transmitted, of which the one in the positive and the other in the negative hull passages of the change. voltage is discharged and the output voltages of the storage capacitors are each connected via a diode (D 1, D 2) and another voltage. follower (Y 4) is guided to an output resistance (E 2). 2. Circuit arrangement for measuring the frequency using the circuit arrangement _0. According to point 1, characterized in that the the maximum value of the sawtooth voltage occurring at the end of each half-cycle of the AC voltage. ·. · Which overruns the voltage at the output,. ',. , '. stand (R 2) appears, with a Hegler through Adjustment of the rate of increase of the sawing tooth voltage is controlled to a constant value and one of these steepness proportional voltage value is used as a frequency-proportional output value · For this 1 page drawings