SU1589218A1 - Method of measuring volt-ammetric characteristics of two-terminal networks - Google Patents

Abstract

The invention relates to methods for measuring electrical quantities and can be used to measure the current-voltage characteristics (I – V) of non-linear two-pole devices, for example, semiconductor, electronic, gas discharge devices, and electrical probes in a plasma. The aim of the invention is to improve the accuracy of measurement of the IVC. The essence of the method lies in the fact that, in addition to determining the values of the voltages and currents of the two-port circuit being investigated, when setting one of these values as a discrete series of values and measuring a different value for each value specified, the IV characteristics of the two-pole circuit being measured during each measurement resistors of different resistance. In this measurement, all three IV characteristics are carried out at the same values of a given value. The measurement time for all three IVs is chosen according to the formula given in the specification.

Description

The invention relates to a technique for measuring electrical quantities and can be used to measure current-voltage characteristics. (I – V) of nonlinear two-terminal networks, for example, semiconductor, electronic, gas discharge devices, electric probes in a plasma.

The purpose of the invention is to improve the measurement accuracy of the IV.

The essence of the method lies in the fact that, in addition to determining the values of the voltages and currents of the studied two-terminal circuit, when setting one of these values as a discrete series of values and measuring the other for each

the values of the specified, for each measurement of the IVC of the studied two-pole, additional measurements are made of the IV characteristics of two long-range resistors of different resistance, while measurements of all three IV characteristics are carried out at the same values of the specified value.

The measurement time t of all three IVCs is chosen from the following conditions:

t (0,50,1) ,,

"F, w5

where tf ,, ,, the maximum allowable. relative error voltage and current

about/.

 t

d, are the relative values of the drifts of the parameters of the instrument for setting (measuring) the current and voltage per unit time. To increase the accuracy in the range of currents and voltages up to their maximum values, and (xc, the resistance of the first resistor is chosen to be equal to / IMWKC to reduce the effect of the output impedance r of the voltage source on the magnitude of the specified residual negative error R for the Case where the voltage is set, and the current is measured, is chosen from the condition:

R, +

(fu (R. + r)

ti

R, R2

, (one

To reduce the effect of S current meter to the residual relative cfj, the resistance of the second is chosen from the condition:

The absolute error of the voltage 4U., And the current L., is calculated from the shape of the floor;

and

41p where I ..

RI RJ:

(I

R-z-R 1

In, R, -lyiiRi R, -R,

- in, -u .;

(h:

I - currents through the first and second resistor at a given voltage U.

In the case where the voltage is measured and the current is set, the conductivity of the second resistor G is chosen from the condition of reducing the influence of the conductivity of the current source g to the residual value f-j by the formula

G, G 2: G,

(Gi + g)

g

(BUT)

where G is the conductivity of the first resistor.

In this case, to reduce the effect of non-linearity, measure the voltage of Sy up to the given residual maximum allowable value Oj of the second resistor. C is selected from the condition:

(one

Jul sy-l

-)

(five)

Absolute errors are calculated by the formulas:

(6)

and the second resistors at current 1.

Consider the case of setting the voltage and current measurement.

Let the current-voltage characteristics of the studied two-pole and two resistors with resistance R and R at K points be measured and for each current-voltage characteristic know the values of the specified voltage U, ..., U, and K values of the measured current I., ...} ... 1, , The measurement time is chosen taking into account the thermal constant of the instrumentation time such that the temperature and time drifts of its parameters can be ignored. The set values of the voltage and the measured values of the currents I differ from their true values U p, and if by the absolute errors, and, and / II f ,. In this way

U

n in

 and.

h + li + L.

-n -n For each point of the IVC resistors can be written:

Um, + 4Un, R, (lrt ,,)

. ,, 4-л1 „,

),

n (1 g where the indices 1 and 2 mark the values obtained, respectively, for the current-voltage characteristics of the first and second resistors.

five

. Since all three IVCs are measured at the same voltage, then U

 and,

,,

0

five

., The errors a and g, and 4U differ only because of the influence of the internal resistance g of the voltage source when switching from the first resistor to the second in the n-th point of the I – V curve, since the R value is chosen equal to UAAOKC / TMCIKC. then R i must be greater than R, which ensures the normal operation of the current meter in the entire voltage range.

Increment sought

du, and

 (

where and,, and r (- voltages respectively on the first and second

rum resistor in the nth point of the IVC, "

Ujj is the no-load voltage of the voltage source at this point BACH.

The value J is approximately equal to the relative change in the voltage when the load resistance changes from R to R and causes the occurrence of the relative error J caused by the final output resistance of the voltage source

4Un

J1, - (,

Xx

Considering that R R can be considered

"Dxr

Rt-r.

U-- (RT + r) From this expression we find cfb ()

+ R,.

5892186

my residual current measurement error. If all three HAC are measured in a time less than or equal to that found, we can assume that 41 n

and 41

M

dln hi ™ errors due to the deviation of the current meter scale from the specified value. The deviation of the scale of the current meter can be, l expressed relative non-linear - i .M

since g

 3m

15 where I is the measured value, i is the input current, M is the specified measurement scale

current.

For a current meter that includes a 20 terminal display device that takes into account conversion weights (for example, a quantization step corresponding to a low-order bit), the M 1 condition must be met. Then the nonlinearity

Thus, if R meets the above condition, equating di k and “results in a residual relative error less than Py.

Error 41 1 "can be represented as

41p,

IN

de 41

/ B.- ..,

So.

41,

"but

  -additive composition and absolute absolute

error meter current in the p-th point BAC of the first and second resistors;

-multiplicative components of the absolute error 45 by varying the resistance on the value of

to 2 to R, with a voltage U, is di and,

current meter in the pth point BAC of the first and second resistors.

The errors 41, d 41 are caused by the zero offset of the current meter due to inaccurate adjustment, temperature and time drifts of the equipment parameters. For each type of equipment. Theoretically or experimentally, it is possible to determine the time during which the time and temperature drift of its parameters are much less (for example, ten times) allowed

d I d i

For each type of equipment, a maximum value S can be found, equal to

J

 -one

S t max I - 1 JMaKC I and 1

Hereinafter, the nonlinearity S, j means the maximum value of this value (index max is omitted).

The increment of the current di at the input of the meter leads to the error J4i

increments of measured value 41

d I d G

/ 3 4 i di

- 1 41 - di.

The increment of the current 4i, caused by the change in 45 resistance

SO

to 2 to R, with a voltage U, is di and,

Denoting 4R R, H taking into account that, is approximately equal to I (up to 4ln error).

get

five

41

4R

44i

4R

i R, -tdR

The value 4di / If ,, is equal to the relative error caused by the non-linearity of the meter. (

Designating lI / IL. , get s / o s

J J K. + LK:

Given a value of A and knowing the value of S.J, one can determine the admissible value of Rj.

Taking into account that i3R, from the previous formula are found

R "- Therefore, if the compliance

3

Rj R, (1 + q-zir),

-j: can be considered 41 „, 41„.

41

Chsh

 2.W

P1

Such an assumption leads to an accurate relative error of current measurement, not exceeding the value of j.

For the fulfillment of the specified requirements for the measurement time and the resistance values R :, R the equations for HAC resistors take the form

Uh + 4Un R, (); and whether "E, ().

From these equations one finds

L1.

R-j-R,

RI .i.j, 3i .., 11 R -R,

Thus, for each value of the voltage being set, the absolute error of setting this voltage Uyi can be found. Since the values of I "and I" overlap the entire scale of measured currents j, it can be assumed that absolute current measurement errors were found for 2K points of this scale.

The ratios for the case of setting the current and measuring the voltage were obtained similarly, taking into account the invariance of the laws of electrical engineering regarding the simultaneous replacement of voltages by currents and resistances by conductors.

The analysis shows that when applying the proposed method, the errors of setting one value and measuring another can be found and, therefore, taken into account

points of the range of variation of these quantities, which leads to an increase in the measurement accuracy of the IVC without increasing the accuracy of the equipment.

The method measures the I – V characteristic in the following order: According to the maximum value of the specified voltage, the measured current, the known output impedance r of the voltage source, the maximum value of the relative nonlinearity S, the current meter and the specified relative residual errors, fi., TP- | voltages and currents determine the resistances of the reference resistors R and R

1 lvvs MdKc

./one"

R, (1

R, +

f (; (Ri + r)

Over time, eliminating the influence of thermal and temporal drifts of the parameters of the equipment, the IV characteristics of the studied two-pole and reference resistors are measured in any sequence at the same voltage values.

Calculate the absolute error of voltage setting and current measurement when measuring the current-voltage characteristics of resistors using the formulas

Adjust resistor current values

Ch Cor 1n / 1 „-ДД1

and kof

h s

h °.

For each current of the studied two-terminal I j g, a current is found and from the sets 1 ", I-J, under the condition minimum

ma values for the currents of the resistor R, K 2 for the currents of the resistor R, in the general case j S n.

Adjust the current values of the two-pole device under study.

  Jh

kop where I

where D1 f, is the absolute error of the emaranium current I c, and Correct voltage values on the studied two-port

and ,, g (,)

 - corrected standard of KOR

 dvukhpolusnik current at voltage U.

According to the calculated values, a table is compiled for the IVC of the bipolar circuit under study.

For the case when the current is set and the voltage is measured, the measurements are made similarly. Resistors are selected using formulas (4) and (5), absolute errors are found using formula (6). In order to reduce the effect of the conduction g of the current source to the value of a given residual relative error / / j in measuring the voltage and setting the current, the conductivity of the second resistor G is chosen from the condition

h (s, + g)

g

In addition, in order to reduce the effect of the nonlinearity S of the voltage meter to a predetermined residual relative magnitude under the conditions specified above, the conductivity of G of the second resistor is chosen from the condition

 and

G, G,

G

G, G, G,

(1 +

The absolute errors of the current and voltage for the case specified above are calculated using the formulas C, Un, -GiUyi Gt-G,

dUr,

 G, Gj

Gj-g

(Un,

g

and.

pg

tension on the ground. and the second resistor at current I g ..

Claims (1)

1. A method for measuring the current-voltage characteristics of a two-pole device, which implies that a number of fixed voltage values are set at the test two-port network, measures the current through the test two-port network, and using the measured values, the current-voltage characteristic of the two-terminal device is measured. about the fact that, in order to increase the accuracy of measurements when Each measurement of the current-voltage characteristics of the two-pole device under study additionally measures the current-voltage characteristics of each of the two reference resistors, measurements of the current-voltage characteristics are carried out at the same predetermined fixed voltage values, the absolute errors to the results of the measurement of the current-voltage characteristics of the studied two-pole device are determined by the measurement of the reference resistors, the resistance of the first reference resistor is chosen equal to the ratio of the maximum specified voltage to the maximum current through the studied two-port, and the resistance of the second reference resistor is chosen equal to the smaller of the values calculated by the formulas R, J u (R. + r) 2 R, R. (1 Where. R ,, R, 5 0 r Jl five 2 U and y resistance of the first and second reference resistors j equivalent internal resistance of the source of given fixed voltage values; The specified permissible residual relative error in voltage and current, respectively, is the maximum relative nonlinearity of the current meter. Method POP.1, characterized by the fact that the absolute S-. 4U and L1 errors are calculated using 50 formulas lt (inr.) - Ur, 55  fi Im R, -, where U is the specified voltage value from a number of fixed valuesJ eleven measured currents 1589218 respectively through the first and second reference pe12 Sistors for a given value of the voltage U. p