JPS58181198A - Resistance simulator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resistance simulator suitable for use in testing temperature alarm devices using resistance temperature detectors.

Conventionally, there has been a device of this type as shown in FIG.

In the figure, (1) is a voltage-controlled variable resistance element in which the resistivity of the current path between the first electrode and the second electrode is changed by the third control electrode, and (2) is the terminal of the variable resistance element (1). The voltage detection circuit (8) is a variable resistance element (
1) is a current detection circuit that detects the current flowing through the circuit; (4) is a data input (4) that sets the resistance value of the variable resistance element (1);
% (6) is an analog-to-digital converter (hereinafter referred to as converter) whose output is controlled by the variable resistance element (1) by controlling the voltage supplied to the third electrode of the variable resistance element (1). The operational amplifier s (7) and (8) are the output terminals of the resistance simulator, R□ to R3 are resistors, and the variable resistance element (1) and the voltage detection circuit (2) are used to adjust the resistance value of the variable resistance element (1). and an operational amplifier (6) to form a first closed loop, which connects the variable resistance element (1) and the current detection circuit (
8) and the operational amplifier circuit (6) form a second closed loop), and the operational amplifier (6) is connected to the voltage detection circuit (2).
), the current detection circuit (8), and the Aβ converter (4).
) to control the third electrode.

In the configuration shown in Figure 1 above, now terminals (6), (γ)
If the voltage between EH (v) and the current flowing into the s terminal (6) are R (A), then the output voltage of the voltage detection circuit (2) is x
It is expressed as v-gR (the output voltage of the vl current detection circuit (8) is - RCV) (however, Kv and RCV are proportional constants), and the output voltage of the A/'D converter (4) is −
E is the resistor R3, and the output of the voltage detection circuit (2) is the resistor R□
, the outputs of the current detection circuit (8) are input to the operational amplifier (6) via the resistor R2, and here the voltage detection circuit (2), the resistor R, the operational amplifier (6), and the variable The first closed loop formed by the resistance confectionery (1), the current detection circuit (8
), the resistor R2, the operational amplifier (6), and the second closed loop formed by the variable resistance confectionery (1) act simultaneously, so that at point X shown in the figure, equilibrium is achieved under the following conditions.

Therefore, the resistance value between terminals (6) and I (γ) can be expressed by the following formula. 4) Output voltage - ED at terminal (6)
, (γ), that is, the variable resistance element (1)
This means that the resistance value can be set.

However, since the conventional resistance simulator is configured as described above, it must be used under the condition that the current lR flowing through the variable resistance element (1) is constant, and its range of application is limited. There was a drawback.

Therefore, the present invention has been made in order to eliminate the drawbacks of the conventional ones as described above, and the purpose is to provide a resistance simulator that can set the resistance value regardless of the current value flowing through the variable resistance element. In order to achieve this purpose, the first
A switching element is provided between the detection circuit of either the closed loop or the second closed loop and the operational amplifier, and the amount of feedback to the operational amplifier is adjusted by controlling the switching duty cycle of the variable resistance element. This feature is characterized by setting the resistance value of .

Hereinafter, an embodiment of the present invention will be described with reference to FIG. 2, in which the same parts as in FIG. 1 are denoted by the same reference numerals.

In FIG. 2, (9) is provided between the current detection circuit (8) and the operational amplifier (6) forming a second closed loop, and changes the amount of feedback to the operational amplifier (6). The opening/closing duty cycle of the opening/closing element is changed by the control input α0). Others are the same as before. In addition, the A/1) converter (4
) are not included.

In such a configuration, the operational amplifier (6) is connected from the current detection circuit (8) forming the second closed loop via the switching element (9).
) is input to the voltage detection device (2), which is not indicated by the above formula.
, resistor R□, operational amplifier (5), variable resistance confectionery (1), current detection device (8), switching element (9), operational amplifier (5), variable resistance There is an equilibrium at point X with the closed loop of 5g2 consisting of confectionery (1) under the following conditions.

RIR,T Therefore, the resistance value between terminals (6) and (γ) is expressed by the following formula.

In other words, if the resistance value between terminals (6) and (7) is different from the switching element (9), the switching element (
By controlling the opening/closing duty cycle of the variable resistor 6- element (1), the resistance value of the variable resistor 6-element (1) can be set and is not affected by the current value flowing into the variable resistor element (1).

In the above embodiment, the switching element (9) is provided in the second closed loop to control the input current from the current detection circuit (8) to the operational amplifier (6), but the switching element (9) is provided in the first closed loop. Of course, the same effect can be obtained by controlling the input current from the voltage detection circuit (2) to the operational amplifier (6).

As described above, according to the present invention, the resistance value of the variable resistance element is set by the duty cycle of the switching element provided in either the first or second closed loop. This has the effect of providing a resistive film pseudo device in which the resistance value can be set with high precision without being affected.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional resistive film pseudo device, and FIG. 2 is a circuit diagram showing a resistive film pseudo device according to an embodiment of the present invention. (1)...Variable resistance element (2)...Voltage detection circuit (8
)@@Current detection circuit (5) e・Arithmetic amplifier (9)・
・Switching element In the figures, the same reference numerals indicate the same or equivalent parts. Agent Shin Kuzuno −

Claims (1)

[Claims] A variable resistance element in which the resistivity of the current path between the first electrode and the second electric wire is changed by a third control electrode, one end of which is connected to the first electrode of the variable resistance element to apply a current to the variable resistance element. a voltage detection circuit that sends out an output voltage corresponding to the voltage; a current detection circuit that has one end connected to a second electrode of the variable resistance element and sends out an output voltage that corresponds to the current flowing into the variable resistance element; and the variable resistance element. and the voltage detection circuit and the first
and forms a second closed loop with the variable resistance element and the current detection circuit to computationally amplify the output difference between the voltage detection circuit and the current detection circuit. In addition to being equipped with an operational amplifier that controls the electrodes,
A switching element is provided between the detection circuit of either the first closed loop or the second closed loop and the operational amplifier, and the variable resistance element is controlled by controlling the switching duty cycle of the switching element. A resistance simulator characterized by setting a resistance value.