JPS589349Y2 - Kantiki - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a sensor equipped with an external terminal for adjusting the operating setting potential or sensitivity.

Sensitivity adjustment in a sensor equipped with a semiconductor active element such as a field effect transistor that responds to changes in surrounding physical phenomena and detects them as changes in electrical signals, such as an ionization type smoke detector equipped with a field effect transistor; In other words, work such as setting the operating point or checking the operating point is
Conventionally, testing has been carried out by actually injecting smoke into the sensor and using an ion concentration meter, or by using a simulated smoke element, but especially in on-site work after installation, these methods are difficult to test. Since the sensor itself contains many unstable elements, the operating point check tends to be inaccurate, and since it requires a long time to work on one sensor, it takes an extremely long time to check all the sensors that are installed. Requires hours of work.

On the other hand, another method, as in the case of ionization smoke detectors, is to apply a test voltage to the external electrode of the ion chamber to simulate operation, and to find out the operating point from the value of the test voltage. For example, it is extremely disadvantageous in terms of work efficiency to touch the wiring of internal elements one by one for a large number of sensors after installation.

In view of the above-mentioned situation, the applicant previously proposed a sensor equipped with an external terminal for sensitivity adjustment as shown in FIG. A bias circuit for the field effect transistor 60 sense electrode S that detects a change in the potential balance between the bias adjustment variable resistor 7 and the transistor 6
Since the structure is configured such that the 0-nce electrode S can be connected to the external terminals 4 and 5 via the external terminals 4 and 5, and the external terminals 4 and 5 are always short-circuited during normal times, this short-circuit between the external terminals 4 and 5 can be prevented. If this is not considered, if for some reason this short circuit is removed and the external terminals 4 and 5 are opened, no voltage will be applied to the field effect transistor 6 and the sensor will not operate at all. A problem arises.

This idea was made in view of this problem, and even if the short circuit between the external terminals is removed, the sensor will be prevented from becoming inoperable and will at least issue an alarm, or will remain operational with no effect at all. It is an object of the present invention to provide a sensor using a terminal material for external adjustment.

This invention will be explained in detail below along with the circuit diagrams of the embodiments shown in FIGS. 2 to 5.

On each open shelf, the numbers shown in Figure 1 and the numbers indicate the same effect.
Reference numeral 8 indicates a transistor for transmitting the potential change appearing at the drain electrode of the field effect transistor 6 to the gate input of the thyristor 9, 10 indicates a DC power supply, and 11 indicates an alarm device such as a lamp or a buzzer which is activated when the thyristor 9 is turned on.

In FIG. 2, the sensor of this invention includes a field effect transistor 60 and resistors 12 and 13 as a bias circuit.
One end of the resistor 12 is connected to the power supply potential point 14, and the other end of the resistor 12 is connected to the resistor 13.
The voltage dividing point 15, which is the connection point with one end, is connected to the ground electrode S of the transistor 60, and the other end of the resistor 13 is connected to the reference potential point 17 via the external terminal 4.5, which is short-circuited by the shorting piece 16. It is connected.

A variable output terminal 20 of a variable resistor 19 is connected to the voltage dividing point 15 via a capacitor 18, and a pulse oscillation circuit 23 is connected to one fixed terminal 21 of the variable resistor 19 via a transistor 22. output is connected and the other fixed end 2
4 is connected to the reference potential point 17.

In other words, in the sensor of this invention having the circuit configuration shown in FIG. external terminal 4 to be held;
5 exists, but the configuration is such that a voltage is always applied via a resistor 12 to the ground electrode S, which determines whether the external terminals 4 and 5 are opened or closed.

In the circuit shown in FIG. 2, the source bias voltage in normal use is the voltage at the voltage dividing point determined by the voltage dividing circuit, and the predetermined amplitude adjusted by the variable resistor 19 and supplied via the capacitor 18. The field effect transistor 6 is defined by the weight voltage with the pulse voltage having
falls into a detectable state periodically corresponding to the period of the pulse voltage.

Incidentally, the capacitor 18 adjusts the sensitivity by removing the short circuit between the external terminals 4 and 5 and applying an external voltage. In order to prevent inaccurate adjustment, the voltage dividing point 15 and the variable output terminal 20 are separated in terms of direct current, so that only the pulse voltage from the pulse oscillator 23 is applied to the ground electrode S. belongs to.

In FIG. 2, if the shorting piece 16 comes off due to vibration or other reasons during normal use, the sensor 1 will not become inoperable and the voltage dividing point 15, that is, the base bias voltage will reach the potential of the power supply potential point 14. As a result, the field effect transistor 6 becomes conductive, and accordingly, the thyristor 9 becomes conductive and the alarm 11 issues an alarm in the same manner as when the sensing operation is performed.

In other words, if only one of the many sensors installed is working and the ones nearby are not,
With the sensor of this invention, an abnormal state in which the above-mentioned short circuit is no longer maintained is detected.

The embodiment shown in FIG. 3 uses the external terminal 4 in the circuit configuration shown in FIG.
By connecting a resistor 25 between the external terminals 4 and 5 and appropriately setting the resistance value of the resistor 25 to a value smaller than the resistance value of the resistor 13, the sensor can operate even if the short circuit between the external terminals 4 and 5 is removed. This is an example in which the error is not considered abnormal.

The embodiment shown in FIG. 4 is obtained by removing the shorting piece 16 from the sensor shown in FIG. is operational.

In the embodiment shown in FIG. 5, the resistor 25 in the embodiment shown in FIG. 4 is short-circuited and the voltage dividing point 15 is connected to the external terminal 4.
If the resistors 12 and 13 are low-noise resistors, a sensor can be similarly constructed without a shorting piece.

As described above, in this invention, when adjusting the set operating point by applying an external voltage corresponding to a predetermined operating point and adjusting the variable resistor during sensitivity adjustment work such as operating point check, the above-mentioned external Since it is equipped with external terminals that serve as voltage application terminals, there is no need to change wiring or other factors that reduce work efficiency when performing this type of adjustment work. The sensor does not become inoperable, but at least the sensor either issues an alarm as an abnormal state or continues to be operable. It can even eliminate the need for short circuits, etc.
It is clear that significant practical effects can be achieved.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a circuit configuration diagram of a sensor showing a conventional example, and Figs. 2, 3, 4, and 5 each show separate embodiments of this invention. It is a circuit groove diagram of a sensor. 12.13... Resistor, 19... Variable resistor, 2 25... Resistor. 18... Capacitor, 3... Pulse oscillation circuit 1

Claims (1)

[Scope of utility model registration request] In a sensor equipped with a semiconductor active element such as a field effect transistor that responds to changes in physical phenomena in the surroundings and detects them as changes in electrical signals, a power supply potential point is applied to the electrode to which the bias voltage of the semiconductor active element is to be applied. The voltage dividing point of a voltage dividing circuit consisting of a series circuit of a plurality of resistors connected between the electrode and the reference potential point is connected to apply a predetermined DC voltage to the electrode, and the pulse oscillation The variable output end of the variable resistor connected to the output of the circuit is connected to the above electrode via a capacitor, and a point between the voltage dividing point of the voltage dividing circuit and the reference potential point is connected to the reference potential point. A sensor characterized in that each of the sensors is led out to an external terminal.