SU83576A1 - Method for measuring internal resistances of electric current sources - Google Patents

Description

Suppose that when choosing the magnitude of the volumetric values of / i and / 2, i.e. E; e. + l /, the equality a.mpE R, г (1 + /. v) R is established:

No. 83576-2 -

Hence, after non-Southern transformations follows: or when n 1

Thus, to measure the internal resistance of an alternating current source, it is sufficient to turn it on according to the scheme of FIG. 1 and notice the deviation of the indicator pointer. Then, converting the circuit of FIG. 1 as shown in FIG. 2, by changing the resistance value Ri, it is necessary to again achieve the same deviation. The magnitude of R, at which the indicator pointer deviates by the same angle as in the first measurement, is equal to the internal resistance of the current source.

Using the principle outlined above, a simple circuit can be constructed to measure the resistance. 1 between alternating points, make it difficult. -C12pi of alternating current, the potential difference of which is not equal to zero.

A diagram of such a measuring device is presented in FIG. 3

The device consists of an alternating current indicator (thermoelement with a galvanometer D), an alternating resistance Ri, graduated in ohms, a contact group controlled by a button K, and two clamps for connecting a measured resistance

When the button K is depressed, the spring 3 is connected to the spring by the action of its own elastic force. Springs 2 and 4 remain open.

In this case, the resistance, thermoelement and variable resistance R are connected in series.

When the / C button is pressed under the action of the elastic force of the spring i and, as a result of the pressure on the spring 3, contact is made between the springs 1-2 and 3-4.

Here, the thermocouple and the resistance R are connected in parallel with the measured resistance R,. .

Thus, with the help of the contact group, the device's circuit can receive IID corresponding to the diagrams given in FIG. 1 or 2.

The process of measuring resistance is as follows:

) Set the variable resistance value to the same order as the resistance of the thermoelectric heater, and connect the measured resistance R under the current to the terminals of the device.

2) Notice the openness of the arrow of the galvanometer G and, pressing the button K, return the arrow with the help of a variable resistance to division, corresponding to the first deviation.

3) The value of the measured resistance is read on the scale of resistance R.

When measuring small R, the value of resistance / included when the button is pressed in series with the thermoelement is chosen

eleven

equal-g or -j-ggQ-resistance of the heater; when measuring

large / V the initial value of resistance R is taken equal to 10 or 100 heater resistances.

In these cases, the measurable resistance is determined by the formula

R .. nRi, where n - e - j (j (-, 10 or 100.

The circuit is intended to measure resistances over a wider range with a small relative error (Fig. 4).

R ,,

/, - / v,

The circuit of FIG. 4 differs from that of FIG. 3 only by an indicator used as a low-frequency tube amplifier with a low input impedance.

The constant term of the anode current passes through a milliammeter with an O-1 ma scale or a galvanometer shunted to limit the amount of current flowing through the galvanometer, the sky. resistance.

When using a high frequency antenna with an anode detector, the device described can be used to measure in a large range of resistances at a high frequency, and, which is especially valuable, can be used to compare the resistances of various antenna devices.

Subject invention

Claims (3)

1- A method of measuring internal resistances of electric current sources by comparing with a reference resistance, characterized in that the reference resistance and the indicator connected to the source circuit with the measured internal resistance are switched from the series connection to the parallel connection and, if connected in parallel, select a reference resistance of such magnitude at which the indicator readings at the indicated switchings remain unchanged. 2. The implementation of salvation under item 1, characterized in that, in the case of measuring small internal resistances of the sources, the value of the reference resistance R when switching to a series connection with the indicator is chosen to be in / g times lower than the resistance value of the indicator; internal resistances are n times the value of eto, and the internal resistance of the source is calculated using the formula dx for measuring small internal resistances, and using the formula R nR for measuring measuring large internal these resistances. 3. When applying the method according to claims. 1-2, and with the fact that, when measuring the internal resistances of the alternating current sources, the impedance proportional to the modulus and the internal resistance of the source is used as the reference resistance. - 3 -L ° 83576 P l -WA / W