JPS59200971A - Demand transducer - Google Patents

Abstract

PURPOSE:To make a demand measurement such as of AC current or electric power easy by obtaining an output voltage proportional to an DC input at a time limit characteristic to be optionally selected. CONSTITUTION:A subtractor 1 generates an output proportional to the difference between an input voltage Ei and an output voltage Eo. A pulse width modulating circuit 2 inputs a pulse output with a duty ratio proportional to the output of the subtractor 1 to a counter 4. The counter 4 counts up pulses of an oscillator 3 when the output of the modulating circuit 2 is the H level and counts down the pulses at the L level. A D/A converter 5 converts the output of the counter 4 into an analog voltage. The time limit characteristic of the output voltage can be optionally changed by changing the constants of respective circuits 1-5. If an AC/DC transducer or a power/DC voltage transducer is connected to the input side, a demand measurement such as AC current or electric power can be easily obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a demand transducer used for measuring demand of alternating current or electric power.

Generally, when measuring the current of a circuit such as a welding machine where the load fluctuates rapidly, the reading changes rapidly and is difficult to read using a general-purpose ammeter. For this reason, conventionally, instruments with slow response speeds (large time constants), such as thermal instruments using bimetals, have been used.

By the way, in instruments using bimetals, it is necessary to increase the precision of the bimetal in order to make the instrument time constant (hereinafter referred to as time limit) uniform, but there are major constraints due to problems in the selection of bimetal materials and processing. is recieving. This instrument also uses the secondary voltage AC11 of the instrument transformer as an input signal.
Since 0V, current AC5A, etc. are often input, so-called remote measurement, where the measurement site and monitoring location are far apart, has a large loss in the line connecting the measurement site and the instrument, so this type of measurement method is It was unsuitable. Furthermore, there have been problems such as the inability to supply data to electronic computer systems such as data loggers, which have become rapidly popular in recent years.

The present invention has been made in view of the above points, and an object of the present invention is to provide a demand transducer having a simple circuit configuration and uniform timing characteristics. In other words, by obtaining an output DC voltage (or current) proportional to the input DC voltage (or current) with arbitrarily selected time characteristics, it is possible to easily measure demand for AC current, power, etc. It can also support remote measurement, and in particular can supply data to data loggers and the like.

Hereinafter, a demand transducer according to the present invention will be explained with reference to the drawings.

First, as shown in Figure 1, the horizontal axis shows time t, and the vertical axis shows output E.
. In the graph representing the output E when time 1=0
Starting from o=O, when t=t1, E o =
When Eo 1.1=12, Eo = Eo t, -・
Think about the trajectory. As shown in FIG. 1, this trajectory approaches the output Eold convergence value Ei without limit if the time t becomes sufficiently large. , 12.1. ...
Therefore, t, -t, -t, = t, -t2= t, -
t, -...-k (where n: positive integer, τ: constant)
Then, the locus of this graph can be expressed by the following equation (1).

(However, m is a positive integer, and Eom and Eom indicate the m-th and (ml)-th outputs, respectively.) If the right side of equation (1) is expressed only by Ei and n, then as in equation (2), Become.

The right-hand sides of Eom and Eon in equation (2) are simplified.

Kichi(++(+-kichi)+...+(1-wan-1)=(1
(li month ((I + (1J-) ten... + (1-luck)"
-')=1-(+-luck)n,',Eom=(l-(1-luck)-)Ei ・(3)E
on-(1-(1-Sat)n)Ei...(4) The demand transducer described below has a time-output characteristic as shown by the curve in FIG. When the input Ei is continuously applied to the transducer for a time t, the output E (1) is m
=! Since this is the value when n is set, it can be expressed by the following equation. , Eom(1-(l-old)τ")Ei Here, in equations 1.
8). For example, when n = 10', 2
71842, 2.71828 when n = 10'. Therefore, equation (6) can be easily expressed as in the following equation (7), like a normal CR integration circuit.

1 Eom(I-e τ)Ei ・(7) In other words, when a certain interval is divided into n sufficiently finely as shown in Fig. 1 and equation (1), each of the (m-1)th and mth outputs The relationship between Eom-s and Eom is Eom
-Eom-1+1 (Ei -Eom-1), and by making it possible to arbitrarily select the time constant τ shown in equation (7), it is possible to support remote measurement and also to use a data logger. It is extremely effective as a demand transducer.

The configuration of the demand transducer according to the present invention will be explained below.

FIG. 2 shows an example of a demand transducer according to the present invention. In the figure, (1) is a subtraction circuit which obtains an output proportional to the difference (Ei-Eo) between the input voltage Ei and the output voltage EoO. (2) is a pulse width modulation (hereinafter abbreviated as PWM) circuit, which obtains a pulse width modulation (hereinafter referred to as PWM) circuit, which obtains a pulse width modulation (hereinafter referred to as PWM) circuit, which has a duty ratio proportional to the output (Ei-Eo) of the subtraction circuit (1), and whose output is at a logic level. M” section is T
If the interval of 1 logic level 1L" is T2, then the following (8
) shall be satisfied.

-T = Kt (Ex, Eo) 09. (8) (L;
constant) T1+T2 (3) is an oscillation circuit, and the period (T
1+T2), it outputs a pulse with a sufficiently short period (high frequency f). (4) is the oscillation circuit (
3) is a counter that counts the pulses, and its counting direction changes according to the output state of the PWM circuit (2), and counts up when the output of the PWM circuit (2) is 1, that is, in the T1 interval, and reaches 'L. ”, that is, in the TJ section, the count is down.

(5) is a digital/analog converter (hereinafter abbreviated as % converter) which converts the digital output of the counter (4) into an analog voltage. In addition,
(6) is an input terminal, and (7) is an output terminal.

Next, the operation of the above configuration will be explained with reference to FIG. The counter (4) connects the pulse of the oscillation circuit (3) to the PWM circuit (
2) When the output is SSd/, that is, in the TI interval, it counts up (FIG. 2B), (C1>), and when the output is 1L'', that is, in the T2 interval, it counts down (FIG. 2B).

(C) ). Therefore, the frequency of the output pulse of the oscillation circuit (3) is f ((A) in the same figure), and the pulse of frequency f is
The output Q of the counter (4) at 6 is counted up by
When O is set to Qom as 2ft, the period of the oscillation circuit (3) is sufficiently smaller than the period of the PWM circuit (2) ('r + 1 T2), so the input Ei is continuously input to the input terminal (6). The output of the counter (4) when the voltage is applied for the time t can be expressed by the following equation (9).

2ft to Qom
, 18) As shown in equation (9), the counter (4
) is the input Ei and the output E of the human converter (5).
It is proportional to the OQ difference.

Therefore, when input Ei is applied to input terminal (6),
As shown in Figure 1 and Equation (1), the interval τ is sufficiently 1t(
Divide 0 into n, and set the counter (4
) is the output of Qom=1, and the output of the % converter (5) is Eom-, then the m-th counter (4)
The output Qom of and the output Eom of the temporary converter (5) are as follows.

Qom=Qom-++ to 1 to 2f(Ei-Eom-+)
, ...-(If)) -force E of a converter (5)
The relationship between o and the output Qo of the counter (4) is EomKQo
(K3; constant), then Eom = 3Qom = (Qom-++, 2f(Ei-Eom-+)
, )(',' Substitution of formula (10)) = Eom-r +, ni2, fr -kichi (Ei -
Eom−1)−(11)(°, °Eom−,=, Qo
m-1) In equation 01), if K1 is set to 2 and f- is set, equation (11) is the same as equation (1) above, and its time-output characteristic becomes as shown in Figure 1. .

In the circuit of Fig. 2, a subtraction circuit (1), a PWM circuit (
2), the oscillation circuit (3), the counter (4), the % converter (5), etc. can all be realized relatively easily using well-known electronic circuits, so the detailed circuits will be omitted here. Each of the circuits (1) to (5) described above can be easily made highly accurate, and the constants of each of the circuits (1) to (5) that determine the time limit τ described above can still be increased by 1. K2f, ni, etc. can be easily and precisely set by simply changing the resistance values used in each circuit (1) to (5).

In the above explanation, only the rising characteristic corresponding to the charging curve in the CR integration circuit shown in FIG. 1 has been described, but the output T1. of the PWM circuit (2). Regarding T2 (E
When i-Eo)=O, T1=T2, (Ei-Eo):
> 0 when T1>T2, (Ei-Eo) (O when T
If you use a circuit such that I<T2, you can do (
Ei-Eo) (0 corresponds to a discharge curve and exhibits a falling characteristic with the same time constant τ.

As described above, the demand transducer according to the present invention can obtain a uniform output with a time characteristic that can be arbitrarily selected using a relatively simple circuit without using any special parts or circuits. Since the output can be used as an analog voltage or a digital value by taking out the output of a counter, it can be widely used as data for data loggers, which have become rapidly popular in recent years, and also for remote measurement.

[Brief explanation of the drawing]

FIG. 1 is a time-output characteristic diagram used to explain the demand transducer according to the present invention, FIG. 2 is a block diagram showing an example of the demand transducer according to the present invention, and FIG.
The figure is a signal waveform diagram of each part for explaining the operation of the demand transducer. (1)...subtraction circuit, (2)...pass width modulation circuit, (3)...excavation circuit, (4)...counter, (
5)...Digital/analog converter, (6)...
...Input terminal, (7)...Output terminal. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Masuo Oiwa

Claims (1)

[Claims] and a duty ratio parameter proportional to the output of the subtraction circuit)
an oscillation circuit that outputs a pulse with a shorter period than the pulse period of this pulse width modulation circuit, and an output terminal of the pulse width modulation circuit connected to an input terminal for switching up and down counting. and a counter in which the output terminal of the oscillation circuit is connected to the clock pulse input terminal, and a digital/analog converter for converting the output of the counter into digital/analog; A demand transducer characterized in that it obtains an output proportional to an input with a time constant that can be selected.