DE1250921B - - Google Patents

Description

GERMAN OTM PATENT OFFICE

EDITORIAL

German class: 21 e- 36/01

Number: 1 250 921

File number: W 34444 IX d / 21 e

1 250 921 Filing date: May 9, 1963

Opening day: September 28, 1967

The invention relates to a method for measuring the peak-to-peak value of alternating voltages relatively low frequency, on which an interference voltage of very low frequency is superimposed, with the signal path between the signal source and the actual measuring device with the help of a switch can be separated.

In known measuring instruments for determining the peak value (or the peak-peak value) of alternating voltages, the voltage to be measured is continuously applied to one capacitor (or to two capacitors). If the peak-to-peak value of an alternating voltage V ₁ = f (t) is now to be measured (FIG. 1), on which an interference voltage V ₁₁ - f (/) is superimposed, it is known to switch in front of the actual voltmeter a high pass. This is designed so that the interference voltage V ₂ = f (t) is kept away from the voltmeter. However, this (selective) measuring method cannot be used at any frequency. In particular at low frequencies in the order of 1 Hz, where z. B. an interference voltage of 0.1 Hz is superimposed, this measurement method is often not applicable because of the complicated and expensive filter.

A known device for measuring the amplitude of electrical impulses (German Auslegeschrift 1 138 158) contains a switch that controls the signal path between the signal source and the actual Measuring device is periodically separated, the switch allowing current to flow in both directions and is externally controlled by the pulses to be measured. This known device has the disadvantage that the only closes after the beginning of a pulse and before the end of a pulse re-opening switch is actuated in this way for each individual impulse that occurs, so that the arrangement works practically continuously and does not eliminate low-frequency interference voltages.

With the method according to the invention, the peak-to-peak value of AC voltages can be relatively low frequency, on which an interference voltage of very low frequency is superimposed, with little effort can be determined by the fact that the peak-to-peak value is not continuous, but too arbitrary selectable, e.g. B. points in time that are several periods apart only during half a period the voltage to be examined in a known manner by charging a capacitor to the positive peak value and a further capacitor to the negative peak value as well as subsequent Adding the two values is measured.

Method of measuring the amplitude of
Alternating voltages

Applicant:

Wandel and Goltermann, Reutlingen

Named as inventor:
Dipl.-Ing. Albin Lang, Pfullingen

On the basis of fig. 2 to 4 are intended to describe the method according to the invention and two arrangements for carrying it out of the same to be described.

In Fig. 2 an alternating voltage V ₁ = f (t) is shown, the peak-to-peak value t / _{ss of which are} measured

ao the should. The influence of the interference voltage V ₂ = f (t), which has a much lower frequency, should be eliminated. An arrangement according to FIG. 3 is to be used for this purpose: In the initial state, the gates T ₁ , T ₂ , T ₃ and T _i (electrical

»5 tronic switches) non-conductive. D "ie control of all the gates which will be explained below for a better clarity unspecified, can be measured and be made of the noise voltage on the control unit S of the voltage to be measured V ₁ = f (t) or from the. At time 1 ( Fig. 2) for example, the gates of T ₂ and T are conductive so that the capacitors C ₁ and C ₂ discharge ₃ via the resistors R ₁ and R _2. After the time t _k (F i g. 2) open ( From time 2 to time 3 , gate T _{1 is} closed (conductive) and capacitor C ₁ charges to the value V _{s t} . From time 3 to 4 , gate T ₁ is open again and closed again from time 4 to 5 , as a result of which C _{2 is} charged to voltage V _s via diode D _9. From time 5 to 6, T _{4 is} closed and a high-resistance measuring instrument M is used to measure the capacitors across capacitors C ₁ and C ₂ standing voltage V _sl + V _s9 = V _ss measured - The next measurement can, for example, after be made according to some periods.

If small alternating voltages V ₁ = f (t) are to be measured, the relatively high forward voltage of the diodes D ₁ and D ₂ in FIG. 3.

In this case, it is advantageous as shown in FIG. 4 to use switches (gates) T ₅ and T _{b instead of these diodes.} Contain switches T ₅ and T ₀

709 649/150

Claims (5)

For example, transistors - but other switches such as relays are also conceivable - then the residual voltage collector / emitter is present as the disturbing voltage, but this is much lower than the forward voltage of diodes. The switches T5 and T0 are, corresponding to the gate T1 in Fig. 3, alternately opened and closed via the control unit. Incidentally, the works in F ig. The arrangement shown in FIG. 4 as well as that according to FIG. 3. If the switches T5 and Tlj are designed so that they are conductive in both directions, then charging or discharging of the capacitors C1 and C1 is also possible via these switches. The discharge circuits TJR1 and T3IRi are generally not necessary in this case. It is also possible to short-circuit switches T6 and T0 only in the peak value of the measuring voltage and only to correct the voltages across C1 and C2 if the respective new peak value is not identical to the old one. The gate T4 could be omitted here. The method according to the invention is not limited to the measurement of sinusoidal alternating voltages. In particular, the method can be used to advantage in the case of a pulse-shaped signal whose leading edge has a relatively long rise time. Patent claims: 1st Method for measuring the peak-peak value of AC voltages of relatively low frequency, on which an interference voltage of very low frequency is superimposed, wherein the signal path between the signal source and the actual measuring device can be separated with the aid of a switch, characterized in that the peak-peak value is not continuous , but to freely selectable, z. B. several periods apart times, is measured only during half a period of the voltage to be examined in a known manner by charging a capacitor to the positive peak value and another capacitor to the negative peak value and then adding the two values. 2. The method according to claim 1, characterized in that the time of the beginning and the duration (1/2 period) of a measurement of the voltage to be examined are controlled in a manner known per se. 3. The method according to claim 1, characterized in that the time of the beginning and the duration (V2 period) of a measurement are controlled by means known per se of the interference voltage to be examined and the interference voltage superimposed on it. 4. Arrangement for carrying out the method according to claims 1 and 2 or 1 and 3, characterized in that a gate (T ₁ ) is connected to the ungrounded input terminal, the output of which via a diode (D ₁ ) to a capacitor (C ₁ ) and via a further, oppositely polarized diode (D ₂ ) is connected to a second capacitor (C ₂ ) so that the capacitors (C ₁ , C ₂ ) are connected to one another at one end and the connection point is connected to ground, that parallel to the capacitors (C ₁ and C ₂ ) connected in series via a gate (T ₄ ) a high-resistance voltmeter (M) and parallel to each capacitor (C _v C ₂ ) via gates (T ₂ , T ₃ ) discharge resistors (R _v R.,) are switched, and that all gates (T ₁ , T ₂ , T ₃ , T ₄ ) are connected to the input via a control device (S) (Fig. 3). 5. Arrangement according to claim 4, characterized in that the capacitors (C ₁ , C ₂ ) each via a gate (T _v T _fi ) with the input terminals and the gates (T ₅ , T _li ) with the output of the control unit (S ) are connected (Fig. 4). Considered publications:
German Auslegeschriften No. 1 025 516, 138 158. 1 sheet of drawings 709 649/150 9. 67 © Bimdesdruckerei Berlin