JPH06318888A - Level measuring method for distribution line carrier signal - Google Patents

Abstract

PURPOSE:To correct the influence caused by the difference of impedances even when the matching is not secured between a line impedance and the transmission impedance of a slave station by connecting an existing resistance in parallel to a line to be measured as a level measuring circuit. CONSTITUTION:A slave station transmission impedance Z2 is set at R0OMEGA, and level set by R0OMEGA that secures the matching between a line Z7 and the impedance Z2 is set at A0dBm. Furthermore the level of a slave station transmission signal is apparently set at AdBm when an existing resistance 8 equal to the value (b) times as much as R0 is connected parallel to the line Z7 and the level of the slave station transmission signal is measured with the line Z7 set at a level (a) times as much as R0OMEGA. Thus the relation between A and A0 is shown by an expression I. The relations between the slave station transmission signals A1 and A2 and A0 are shown by the expressions II and III when two types of existing resistances are set at the values equal to b1 and b2 times as much as R0OMEGA respectively and connected in parallel to the line Z7. Then both expressions II and III are solved so that an expression IV is acquired. Then (a) acquired in the expression IV is substituted for the expression II so that an expression V is acquired, and (a) can be corrected into the value acquired by R0OMEGA that secures the matching between the line Z7 and the impedance Z2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the level of a distribution line carrier signal when the line impedance is not matched with the slave station transmission impedance in the level measurement of the slave station transmission signal in the distribution line carrier system of a distribution automation system. Regarding measurement method.

[0002]

2. Description of the Related Art FIG. 2 is an explanatory diagram showing an example of a level measuring method of a slave station transmission signal in a conventional distribution line carrier system. In FIG. 2, the slave station 1 transmits a signal from a transmission source 3 having a transmission impedance 2 to a line having a line impedance 7. When the level meter 4 is connected in parallel with the line and the line impedance 7 is matched with the transmission impedance 2 of the slave station 1, calculation is performed by the calculation unit 6 from the voltage measurement value 5 of the signal in the level meter 4. , The transmission signal level of the slave station 1 is obtained.

[0003]

However, in this conventional method of measuring the level of the slave station transmission signal in the distribution line carrier system, when the line impedance 7 is not matched with the slave station transmission impedance 2, the line impedance 7 is not measured. The voltage measurement value 5 is affected by the magnitude of the.
Therefore, the slave station transmission signal level calculated by calculation is
When the line impedance 7 is larger than the slave station transmission impedance 2, it becomes larger than the actual value, and conversely, when it is smaller, it becomes smaller than the actual value. Therefore, according to the present invention, even when the line impedance 7 is not matched with the slave station transmission impedance 2, the slave station transmission signal level is measured in the same manner as when the line impedance 7 is matched with the slave station transmission impedance. It was made possible.

[0004]

In the present invention, two kinds of known resistors are prepared outside the level meter, and the line impedance is calculated from two level measurement values when the resistors are connected in parallel with the line. Correct the effect of deviation from the slave station impedance of.

[0005]

As described above, even if the line impedance is not matched with the slave station transmission impedance, the slave station transmission signal level is measured by the method of measuring two kinds of level measurement values in which the known resistance is connected in parallel with the line. Can be corrected to a value when the line impedance matches the slave station transmission impedance.

[0006]

1 is an explanatory view showing an example of a level measuring method of a slave station transmission signal in a distribution line carrying system of the present invention, which is a measuring method in which a known resistance is connected in parallel with a line. In FIG. 1, 1 to 7 are the same as in FIG. Reference numeral 8 is a known resistor connected in parallel with the line. The slave station transmission impedance 2 is R0Ω, and the level when the line impedance 7 is R0Ω which is matched with the slave station transmission impedance is A0 dBm. Also, when the line impedance 7 is a times R0Ω, a known resistance that is b times R0Ω is connected in parallel with the line to measure the slave station transmission signal level. Then, the relationship between A and A0 is obtained by the following equation. A = A0 + 10 × LOG ((a × b) / (a + b)) (1) Two kinds of known resistances are b1 times and b2 times R0Ω, and these two kinds of resistances are connected in parallel with the line. When the measured values of the slave station transmission signal level at this time are A1 and A2, A1 and A2
The relationship between A0 and A0 is expressed by the following two equations from (1). A1 = A0 + 10 × LOG ((a × b1) / (a + b1)) (2) A2 = A0 + 10 × LOG ((a × b2) / (a + b2)) (3) (2), (3) ) Equation is solved to obtain the following Equation (4).

[0007]

[Equation 1]

Substituting the value of a obtained by the equation (4) into the equation (2), A0 = A1-10 × LOG ((a × b1) / (a + b1)) (5) From the equation (5), even when the line impedance 7 is not the same as R0Ω as the slave station transmission impedance 2, the line impedance 7 can be corrected to a value when R0Ω is matched with the slave station transmission impedance 2.

[0009]

As described above, according to the present invention, it is possible to correct the influence due to the impedance shift, and therefore the line impedance in the distribution line carrier system is not matched with the slave station transmission impedance. The station transmission signal level can be corrected to the slave station transmission signal level when the line impedance matches the slave station transmission impedance.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a level measuring method of a distribution line carrier signal according to the present invention.

FIG. 2 is an explanatory diagram showing an example of a conventional level measuring method of a distribution line carrier signal.

[Explanation of symbols]

 1 Slave station device 2 Slave station transmission impedance 3 Slave station transmission source 4 Level meter 5 Voltmeter 6 Arithmetic unit 7 Line impedance 8 Known resistance

Claims (1)

[Claims] 1. When measuring the level of a slave station transmission signal in a distribution line carrier system of a distribution automation system, when the line impedance is not matched with the slave station transmission impedance, two types of known resistors are provided outside the level meter. And a level measuring method of a distribution line carrier signal for correcting the influence of the deviation of the line impedance from the slave station transmission impedance from the two level measurement values when the resistance is connected in parallel with the line.