JPH0219909Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a multi-point measuring device, and more specifically, a burnout signal and an input signal selected by a selection circuit are connected to a capacitor whose one end is connected to a common potential point. The present invention relates to an improvement in a device configured to be applied to an amplifier through an input filter including an input filter, so that burnout can be reliably detected.

FIG. 1 is an explanatory diagram showing the main parts of an example of a conventional device of this type, in which 1 is an input terminal for an input signal, 2 is a selection circuit, 3 is an input terminal for a burnout signal, and 4 is an input terminal for a burnout signal. Capacitor 5 is an operational amplifier.

Input signals from each measurement point are applied to the input terminal 1. The selection circuit 2 selects one input terminal from these input terminals 1 and sends the input signal applied to the selected input terminal to the non-inverting input terminal of the operational amplifier 5. A burnout signal Es is applied to the input terminal 3. This burnout signal Es is also applied to the non-inverting input terminal of the operational amplifier 5 via the resistor R. The capacitor 4 forms an input filter, and has one end connected to a common potential point and the other end connected to a non-inverting input terminal of an operational amplifier 5. That is, the burnout signal Es and the input signal selected by the selection circuit 2 are applied to the operational amplifier 5 via an input filter. Therefore, the capacitor 4 of the input filter is charged by the burnout signal Es and the input signal selected by the selection circuit 2.

By the way, since such a device is configured to always apply the burnout signal Es, the burnout current flowing through the operational amplifier 5 is set to be small in order to suppress errors caused by the burnout signal ( For example, Es=2V, R=
27MΩ). For this reason, when the selection circuit 2 is switched and driven at high speed, the measurement point is switched before the charge charged in the capacitor 4 by the input signal of the previous measurement point has not been sufficiently discharged, and the measurement point is switched at a high speed. Depending on the polarity of the input signal, the capacitor 4 may not be charged with the charge necessary for the burnout operation within a predetermined time even though the burnout operation should be performed, and the burnout operation may not be performed.

In order to solve these drawbacks, the present invention
The charge stored in the input filter capacitor is
The device is designed to be completely discharged after or prior to the measurement, and will be described in detail below with reference to the drawings.

FIG. 2 is an explanatory diagram showing the main parts of an embodiment of the present invention, and the same parts as in FIG. 1 are given the same reference numerals. In FIG. 2, reference numeral 6 denotes a changeover switch which selectively connects the other end of the capacitor 4 to the common potential point and the non-inverting input terminal of the operational amplifier 5. The changeover switch 6 connects the other end of the capacitor 4 to a common potential point to completely discharge the electric charge charged in the capacitor 4 after or before measurement at the previous measurement point, and then connects the other end of the capacitor 4 to the common potential point. Connect to the non-inverting input terminal of the operational amplifier 5 to send the capacitor 4 as a burnout signal.
It is charged by Es and the input signal selected by the selection circuit 2. Thereby, the burnout operation can be reliably performed using a relatively small burnout current without being affected by the input signal of the previous measurement point as in the conventional case.

FIG. 3 is an explanatory diagram showing the main parts of another embodiment of the present invention, in which the same parts as in FIG. 1 are given the same reference numerals. In FIG. 3, 7 and 8 are capacitors forming an input filter, and 9 and 10 are changeover switches. One end of the capacitors 7, 8 is connected to a common potential point, and the other end is connected to the changeover switch 9, 10.
is connected to the movable contact of the Changeover switch 9,
One fixed contact of 10 is connected to a common potential point via a resistor Rd, and the other fixed contact is connected to an operational amplifier 5.
is connected to the non-inverting input terminal of The movable contacts of these changeover switches 9 and 10 are such that when the movable contact of one changeover switch is connected to a common potential point, the movable contact of the other changeover switch is connected to the non-inverting input terminal of the operational amplifier 5. is driven complementary to In addition, the changeover switches 9 and 10 are
The switching is driven according to the selection switching of the selection circuit 2. As a result, while one capacitor forming the input filter is being charged by the burnout signal Es and the input signal selected by the selection circuit 2, the other capacitor is connected to the common potential point via the resistor Rd. This allows for a sufficiently long discharge time. Therefore, the discharge current can be made smaller than in the embodiment shown in FIG. 2, and the discharge can be carried out reliably without putting any strain on the changeover switches 9, 10. Further, since the capacitance can be alternately devoted to discharging after the measurement is completed or before the measurement, the burnout operation can be performed reliably without wasting the measurement time.

In addition, according to the present invention, the charge charged in the capacitor is discharged before switching the measurement point, so it is possible to reduce the spike voltage that occurs at the time of switching. The impact on equipment can be reduced.

As explained above, according to the present invention, burnout can be reliably detected and is effective for various multi-point measurement devices such as multi-point recorders and data loggers.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the main part of an example of a conventional device, FIG. 2 is an explanatory diagram showing the main part of an embodiment of the present invention, and FIG. FIG. 1...Input signal input terminal, 2...Selection circuit, 3
...Burnout signal input terminal, 4, 7, 8...
... Capacitor, 5 ... Operational amplifier, 6, 9, 10
...changeover switch.

Claims (1)

[Claims for Utility Model Registration] (1) A burnout signal and an input signal selected by a selection circuit are applied to an amplifier via an input filter including a capacitor whose one end is connected to a common potential point. A multi-point measuring device characterized in that the other end of the capacitor of the input filter can be selectively connected to a common potential point and an input terminal of an amplifier. (2) The input filter is formed using two capacitors, and the other end of each capacitor is selectively connected to the common potential point and the input terminal of the amplifier in a complementary manner according to the selection switching of the selection circuit. A multi-point measuring device according to claim (1) of the utility model registration claim.