DE2156057C3 - Method for linearizing the display of a measuring rectifier - Google Patents

Description

is _{auptpfades voltage of} H _subt rahiert, so that only

and the output voltages (U _A1 and U _An ) of the error-free main and compensation path, which is proportional to the input voltage, remains in a connection circuit (V) in a compensating The compensated output voltage is to be combined in the useful sense. amplitude around the alternating voltage component of the

The pension path is reduced, which, if necessary, can be achieved through additional measures such as reinforcement.

40 can be matched. In addition, by appropriate choice of the factor by which the Compensation path is controlled with alternating voltage, this amplitude reduction to em

The invention relates to a method for linear minimums are limited. The most practical solution for the display of a measuring rectifier is, in the compensation path, simply • one diode main path and one parallel circuit - two or three diodes of the same type as in the last one, the rectifier error of the main path korn main path in series, so that in the compensating diode compensation path. sation path of the two or three times as large G ¹ calibrated

In the case of measuring rectifiers such as peak value rectifier errors such as in the main path arise. If ttrn, rms rectifiers (BouksJie rectifiers, the rectified output voltage of the compensator), mean value rectifiers, etc. cause the sation path is halved or threed, the diodes in the main path result in rectification. This teacher error, the rectifier error of different sizes on the characteristic curve, can, however, be caused by the curvature of the diodes and the associated temperature dependency and non-linearity of the diode type . three times as large an error as the evaluation error (depending on the curve caused by a so-called Schottky-Bprrier diode or a venous shape and the duty cycle of the germanium diode to be rectified,
the alternating voltage). The merging of the output voltages

In the case of an average value rectifier, the grain 60 of the main and compensation path is in the compensation the voltage drop across the jci diode of the logic circuit depends on the relative Main current path known (Elektronikpraxis, Nr. 6, polarity of the diodes of main and Kompensa-24. June 1970, pp. 72 and 73), parallel to the path through tion. If in the compensation path the diodes a diode and a series resistor formed with the same polarity as those in the main path ver-main current path one can also be turned by a diode 65, the voltage of the compensation and a resistor formed compensation path, for example in a differential circuit, path to switch and this Kcmpensationspfad over from the output voltage of the main path subdie Series connection of another diode and one drained. When the diodes in the compensation path

differently than are polarized in the main path, these voltages were added.

A measuring rectifier according to the invention has good linearity down to the range of a few hundred mV, regardless of the curve shape of the applied AC voltage or the Duty cycle of an applied pulse voltage.

The invention is illustrated below with reference to a schematic drawing of an exemplary embodiment explained in more detail.

The figure shows the basic circuit diagram of a peak value diode rectifier consisting of a main path I and a compensation path II. These two diode paths are connected in parallel with respect to the input voltage U _{E to be rectified.} The actual rectifier circuit of the two paths I and II is selected in a known manner, in the embodiment shown, for example, as a diode rectifier with a downstream storage capacitor C. In the main path I there is a single diode D, on which an error voltage U due to the diode properties such as linearity errors, evaluation errors or absolute value errors ₁ , falls off.

The output voltage U, _u at the output resistor R ₁ is thus:

U ^ = U _n -IU ₁ -.

In the selected exemplary embodiment, two diodes D of the same type as the diode D of the main path I are connected in series in the compensation path II. This means that twice the error voltage falls across these two diodes D in compensation path II

ίο 2 U ₁ , from. At the output of the compensation path II, a voltage divider formed by the two resistors R ₂ and R _n with a voltage ratio of 2: 1 is connected. At each of the opposing areas R " and R ₃ , an output voltage U _A " drops for

which applies:

τι U

_A "

Up

The output voltages U _Al and i / _A "are fed to a differential amplifier V , in which the difference is formed according to the following relationship:

= V _Al - U _An = (U _e -U ₁ ,) - [ψ- υλ =

The resulting output voltage U _{A of} the differential amplifier V, which is displayed, for example, in the usual way with an instrument, is therefore independent of the error voltage and only proportional to the applied input voltage.

Instead of the two series-connected diodes D in compensation path II, at higher frequencies, where such series connections of several diodes could interfere, a single diode of a different type can also be provided, which causes a multiple error. For example, a germanium diode or a so-called silicon Schottky barrier diode could be arranged in the main field I and a single silicon diode, which causes about twice the rectifier error, in the compensation path II. In addition to the voltage divider at the output of the compensation path II, a corresponding voltage divider could also be provided at the input, so that the compensation path is fed with a lower input voltage. It is only essential that the compensation path II supplies an output voltage that is lower than the output voltage of the main path and that this output voltage of the compensation path contains a rectifier fever voltage that is approximately equal to the error voltage in the output voltage of the main path in as many operating states as possible. The error can then be eliminated by subtracting these two voltages. Instead of the diodes, it is of course also possible to use transistors connected as diodes with corresponding properties.

1 sheet of drawings

Claims (1)

1 2 Resistance to feed. Assuming the same Claims: rather resistors and the same diodes with the same Diode properties can be calculated by forming the sum Method for linearizing the display of a current from the main current path and the COM measuring rectifier with a diode main path 5 pensationscurrent path of the rectifier in and a parallel-connected, the rectifier substantially compensated and an essentially error in the main path compensating diode of the applied alternating voltage Proportional off-compensation path, thereby marked output current are generated. Also with this known. in the compensation path (II) either th circuit, however, still remains through the _λ . . . ,. . . . _. . ίο feeding diode for the compensation path caused a) times, in particular twice as many diodes _R ^p est errors that cannot be compensated _{with the S (} £ circuit (D) as in the main path (I), namely with the bar st same diode properties in series- ' ^T _{f be def invention) a} diode measuring ordered and with the same size or, _eichrichter ^ _{u create)} in which the rectifier emer genngerer receipt change payment f. substantial is fully compensated (U _E ) fed smd and their output voltage ¹ ^ ^Ien _d j. Useful output voltage results in the voltage by a voltage switch (R ₂ R ₃ ) _dd input change voltage independent is divided by the division factor »or J _d J _curve ^B _nfo ? _{m or d} ^H _em duty cycle b) the same number of diodes (D) as in the main _{path I), Jg aktjsch linear characteristic} with the same diode properties rr ' ^K arranged and with a by a previous ^{ao e} J ² · _f . _{wjrd starting from one measurement} . correct factor, especially by two _rectifiers) ^B _{with one} main diode path and one _{divided input AC} voltage fed ^ in _{parallel) the} rectifier error of the sma, oa main path compensating diode compensation c) gieicn much uioaen \ JJ) as in nauptptaa ^ l) _ _f! "" _O " _f " ^ "rflnHi.nncnemäR Hnrrh _d per shah sh ÄnspÄei;: t in order and with the same size or ™ ^ ZZ ^ SÄ ^ leTcShter ^ sf STnd ΖΎu ^ nTT ** that is, official "judges."