DE2111393C3 - Method for measuring a voltage with the aid of an analog-to-digital converter and device for carrying out this method - Google Patents

Description

The invention relates to a method for measuring a voltage with the aid of an analog-digital converter, consisting of - preferably a differential amplifier - an integrator and a Comparator, with which method the voltage to be measured and then a reference voltage given to the input of the converter.

In known devices of this type, it is difficult Measure positive and negative voltages as the reference voltage only has a sign and the reference voltage and the voltage to be measured must have opposite signs.

The invention is based on the object of carrying out the method mentioned at the beginning in such a way that that you can get positive and negative voltages without difficulty rr..t only one polarity of the reference voltage can measure.

This object is achieved according to the invention in that the integrator during the measurement process is kept at a potential by means of an auxiliary voltage, the magnitude of which is greater than aN is the voltage to be measured and preferably has the same sign as the reference voltage.

In this way, the reference potential of the analog-digital converter is changed so that the opposite direction the voltage to be measured - regardless of whether it is negative or positive - and the reference voltage is guaranteed.

The relationships are explained in detail using the drawing. It shows

F i g. 1 is a block diagram of a conventional analog-to-digital converter,

F i g. 2 shows the course of the voltage over time at point A of the circuit according to FIG. 1,

F i g. 3 is a block diagram of a converter according to the invention and

F i g. 4 shows the course of the voltage over time at point A of the circuit according to FIG. 3.

In Fig. 1 with I is a preamplifier in the form of a differential amplifier, with 2 an integrator and with 3 denotes a comparator. The three elements form the essential parts of an analog-to-digital converter, with which a voltage applied at point 4 can be measured in digital form. the The arrow on the right in the figure, which originates from the comparator 3, leads to the gate of a counter.

The device shown in FIG. 1 works as follows: First, by closing switch 5, the voltage to be measured is fed into the device. The voltage at point / 4 then increases to the value U ₁ or U _2, depending on the size of the voltage input (see FIG. 2). Then the switch 5 is opened and the switch 6 is closed, with the result that a reference voltage U / t, which is directed opposite to the measuring voltage, is fed into the device. This leads to a decrease in the voltage at point A, where

the sloping curves all have the same slope. The registration-compliant procedure has the

The time difference, .- ,, or /, - /, is then a very significant advantage that you can use.

for the size of the voltage to be measured. any drift in the converter ^ ¹¹¹ ^^ ¹⁰¹ ^ "^""-',,

The procedure described assumes that the reason for this is the following, ideii: Λ: ngeno, mmcn

Measurement voltage always has a different polarity than the 5 of the preamplifier have a university. ^l " ^ILSL ".

Has tension. available as an additional, in the preamplifier.

In order to ensure that the measuring voltage also thinks of the voltage source, then th ■.

can have the same polarity as the reference voltage, additional voltage through de ^ ^uckk ° iJ | ^lu ^ _{bc |}

a circuit can be provided as the / wide input of the preamplifier ι π, -

Fig. 3 shows: The output of the comparator 3 is the result of the subsequent measurement. üu>

with the second input of the differential _{amplifier 1 drift does not appear ν} , ηΓΐ «», ΙΙνιΓι

connected via a switch 7. This connection In further training of the F.rlindimg .st es \ nc. .

is in turn connected to earth via a capacitor 8 if the auxiliary voltage is half as large as (J e m.. _s -

connected. The supply voltage can be as it is from the voltage. In the example shown in the drawing, this means that, by means of a voltage * - .5, Λ, - A ₂ i> t. In certain halls can [^ · '

plate full and partly on the first input of the be expedient if the measuring range χ era oppui

Differential amplifier I are given. will. Then according to the invention K, - «2 * ■

The sequence of the measuring process and the voltage In a further embodiment of the hrlindunu can ι.

Conditions at point A (see Fig. 3) can also be used to describe the procedure described in the following: "" ao resistors are related, and / was dtran

First switches 7 and 9 are closed. that the input (in F 1 g. 3 -Jk) to ground . y ^

The consequence of this is that at the first input of the difference, A _{1 is} an unknown ui-l «·> cm ™ - ^h '

reference amplifier 1 the voltage -U ₀ is applied. Does the resistance or vice versa is Der V orte, 1 u

Analog-to-digital converter based on the feedback resistance measurements then there is .dau one luna the gain is about 1, then -U _{0 is} also 25-sided connected to ground, not significantly - "" ^ sicru.

can be used at the points (see Fig. 3) and at the second input power supply. Aulieraem

of the differential amplifier 1. The capacitor carries is significant that not the other contradiction lands through-

also on one side the voltage -U ₀ current flowing into the measurement: it comes

opposite earth. _{all al | f the} relation ^R> an.

At time t ₀ , switches 7 and 9 are turned 30 "- · ,, hm ™

opens and the switch is closed. At the first the auxiliary voltage can assume any value.

The input of the differential amplifier 1 is now the

voltage to be measured i /., (see Fig. 4). This has pressed «set zero point,

a certain negative potential with respect to earth. It has been explained above that one can cini but with respect to -t / ₀ a positive value. In point / 1 35 correct display of positive and negative voltages

As a result, the voltage rises to the value U ₃ . can thereby be obtained in a simple manner that m. η

At the time /, as in the known method, the counter is set during a certain time interval,

by opening switch 5 and closing the can run backwards. By reversing the polarity of the comp, -

Switch 6 to the first input of the differential output can be given the rated voltage U ₁₁ according to an electric amplifier 1. The winding of the invention can achieve the same result

The voltage at point A drops again. Once they \ n place a feedback loop like they're in

Voltage level -U _{has reached 0} , the time F i g. 3 is shown. several jerk

(/, - /,) which provide a measure for the input coupling loops to be measured D.es can

voltage, related to -U ₀ , ends. then have a meaning if one did the: Sta ^ b I did

The voltage to be measured can also increase positively. The scheme behind the

be opposite earth. The relationship shows the curve, preamplifier and insert before the integrator. 11) cr

which has its peak value at i / <: First, j _m preamplifier decreases, resulting errors add sn M

the voltage in the period / ₀ to /, from -U ₀ to the then to the input drift. Also the Spe can rather B

Value U ₄ . If the reference ( _see Fig. 3) is then at a different point in time Z _1. 7. B. in the amplifier

If the voltage is applied, the voltage at point A 50 is no longer present.

up -! / "down The time difference Z ₅ - /, is a measure So far it has always been assumed that the

for the voltage that has been measured, related to the pw voltage is constant. However, you can use

_nilf _ _v ^vb - further development of the invention also the F.ngangs-

'To the voltage, based on the earth potential, voltage partially the input .ur U ₁ , ^ J ^

to recognize one proceeds as follows: One 55 point between the two "Wic.ersUinde" ^Λ ■ "^

according to the invention selects the ratios so that for and the input for the BezupspotcnUal / h ,, n.

the case Uy = 0 (U _F - voltage to be measured) in order to obtain a non-linear characteristic nc kr

de Zeken /, - / „ and / A, i'-h are (see the dashed input voltage for ^{er /} ; ^d ^ _r t'rti.dunMcrΐτ

Line in Fig. 4). The counter of the digital measuring mechanism can be reversed. In Wcitcrb.ldu. g the Γ. Ijr.

If from the point in time Z ₁ onwards from its maximum level of 60 _dlin g one is an ^ integrator ^ nts running _u «h ^ a J ^

(e.g. 10 000 points) run backwards. At the time / «can be adjusted that the JP ^ opening ^ around the Ik ^

then has it reached zero. Is the voltage of the error to be measured from your So "^ ^ Jj ^^ '^

greater than zero, the counter must be closed at the time / can also be closed

to run forwards again, somehow indicating the voltage potcnt.al one of the meter Λ

must be whether the counting direction is reversed 65 upstream capacitor in the Be a J ^

has or not. Positive and negative errors to be measured by a span «" ^ "^

Tensions will then be corrected by the counter. Furthermore, ^ verse ^^^^

1 sheet of drawings

Claims (10)

Patent claims: 1. Method for measuring a voltage with the aid of an analog-digital converter, consisting of from - preferably a differential amplifier - an integrator and a comparator soft procedure the voltage to be measured and then a reference voltage on the Input of the converter are given, thereby marked that the integr;: lor is kept at a potential during the measuring process by means of an auxiliary voltage, that which measures its amount larger than the / u Is voltage and preferably has the same sign as the tension voltage. 2. The method according to claim I, characterized in that before applying the to be measured Voltage the auxiliary voltage temporarily to an input of one of the units of the Converter (differential amplifier, integrator, Kornp:; rator)> bound memory, especially capacitor, is placed. 3. The method according to claim 1 or 2, characterized in that the auxiliary voltage to one Input of the converter and the voltage at the output of one of the converter units (differential amplifier, Integrator, comparator) fed back to an input of one of the converter units and is stored in a memory, in particular a capacitor, and then the auxiliary voltage switched off i: nd the return line disconnected will. 4. The method according to claim 3, characterized in that the at the output of the comparator pending voltage is fed back to one of the inputs of the differential amplifier. 5. The method according to claim 3, characterized in that the output of the comparator pending voltage is fed back to the input of the integrator. 6. The method according to claim 3, characterized in that two or more feedback loops are provided with memory. 7. The method according to claim 1 to 6, characterized in that the auxiliary voltage is half as much as large as the reference voltage. 8. The method according to claim I to 7, characterized in that after applying the reference voltage the counter reverses its counting direction after the time that corresponds to the time, in which the measuring voltage was applied. 9. Analog-digital voltmeter for performing the method according to claims 1 to 8, characterized in that the output of the comparator (3) connects to an input of the differential amplifier (1) That this connection is connected to a page of memory, preferably Capacitor (8) is connected that in this connection between the memory (8) and the Comparator output 'a switch (7) is located, and that an auxiliary voltage source which can be connected to another input of the differential amplifier (1) is provided whose voltage is greater in magnitude than the voltage to be measured and which preferably has the same sign as the reference stress. 10. Apparatus according to claim 9, characterized in that the auxiliary voltage (- U ₀ ) is taken from a voltage divider (A ₁ , R-.) Fed by the reference voltage. II. Use of a device according to claim IO as an ohmmeter, wherein the one resistor (R ₁ ) of the voltage divider (A ₁ , R.) is an unknown resistance to be determined and the input of the device is connected to ground.