JPH0712600A - Multipoint measuring apparatus - Google Patents

Abstract

PURPOSE:To realize a multipoint measuring apparatus which can accurately measure at a high speed. CONSTITUTION:A multipoint measuring apparatus sequentially selectively applies measurement signals of multiple points to an integrating type A/D converter to convert it into a digital signal, and comprises a limiter for switching an input signal level of the converter ADC to a plurality of stages of limit voltages, wherein a limiting voltage range of the limiter is switched to widely at the time of measuring or narrowly at the time of non-measuring by interlocking to a switching operation of a measuring point.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multipoint measuring device, and more particularly, to a multipoint measuring signal which is sequentially and selectively added to an integration type A / D converter to be converted into a digital signal. It relates to an improvement of the configured measuring device.

[0002]

2. Description of the Related Art FIG. 6 shows a multi-point measuring device such as a recorder.
It is a circuit diagram which shows an example of a force part. In the figure, multiple measurements
Constant channel ch₁~ Ch_mThe measurement signals of
Ji SW ₁~ SW_mCalculation that functions as a preamplifier via
It is applied to the non-inverting input terminal of amplifier U1. Operational amplifier
Between the non-inverting input terminal of U1 and the common potential point,
Capacitor C such as stray capacitance is equivalently connected
It Note that in reality, the noise input to the operational amplifier U1 is
To connect a separate capacitor to reduce
There are many. In addition, the switch SW is connected in parallel with the capacitor C._dAlso
It is connected. The output terminal of the operational amplifier U1 is an integral type
A / D converter ADC is connected and an operational amplifier
Output level of U1 is ± V_limLimited to a specified range of
A limiter composed of diodes D1 and D2 is connected
ing. As an actual limiter circuit,
A well-known idealized diode consisting of a diode, a resistor and an operational amplifier.
Is used.

In such a configuration, the switch SW _d
Are selectively turned on and off depending on the operation mode.
In the operation mode in which the switch SW _d is not turned on, only certain switches of the switches SW _{1 to} SW _m are turned on (for example, SW ₁ ) → all switches are turned off → only certain switches are turned on (for example, in order to avoid a plurality of simultaneous inputs). SW ₂ ) → all switches off → ... Alternately turned on and off. The measurement signal of the measurement channel of the switch that is turned on is amplified by the preamplifier U1 and converted into a digital signal by the A / D converter ADC.

FIG. 7 is an explanatory diagram showing an example of the operation in the operation mode in which the switch SW _d is not turned on, in which a measurement signal exceeding the saturation region in the minus pole direction is input to Nch,
In (N + 1) ch, Nch in the saturation region in the positive pole direction
It shows the case where the values are different from each other. The input of the A / D converter ADC when the switch of the Nch system is on is limited to the limit voltage −Lim on the negative pole side by the limiter. This state is maintained by the capacitor C even when the switches of all channels are off. When the control signals for turning on the switches of the (N + 1) ch system are output while the switches of all the channel systems are off, the (N + 1) ch channels are output.
The switch of the system responds while chattering and shifts to the value of the (N + 1) ch after the chattering ends. At this time, the preamplifier U1 and the A / D converter AD
Since C itself has a time constant, (N + 1) ch
It takes time for the value of to be output correctly. Therefore, a waiting time is provided in which the time obtained by adding the time constant to the end of chattering is sufficiently taken into consideration, and the output after the waiting time is set to the value of (N + 1) ch.

In the operation mode in which the switch SW _d is turned on, the switch SW _d is selectively turned on in conjunction with turning off all the switches SW _{1 to} SW _m, and turned off in other states. That is, as for these switches, only specific switches are turned on (for example, SW ₁ ) → all switches SW _{1 to} SW _{m are} off, and switches SW _{d are} turned on → only specific switches are turned on (for example, SW ₂ ) → all switches are off SW _{1 to} SW _m. Off, switch SW _{d is} turned on and off like →. As a result, the electric charge of the capacitor C is discharged when all the switches are off, and the output becomes 0, so that the waiting time when the switches of the (N + 1) ch system are turned on can be shortened.

FIG. 8 is an explanatory diagram showing an example of the operation in the operation mode in which the switch SW _d is turned on. As in the case of FIG. 7, a measurement signal exceeding the saturation region in the minus pole direction is input to Nch, and (N + 1 ) Ch shows a case where the value is apart from Nch in the saturation region in the positive pole direction. Nch
The input of the A / D converter ADC when the switch of the system is ON is the limit voltage on the negative pole side by the limiter.
Limited to Lim '. When the switches of all channels are off, the switch SW _d turns on. That is, when the control signal for turning on the switch SW _d is output, the switch SW _d turns on while chattering, and after the chattering ends, the charge of the capacitor C is discharged to 0.
become. After that, when a control signal for turning off the switch SW _d is output, the switch SW _d turns off while chattering. Then, after the chattering ends and a margin time for safety further passes, a control signal for turning on the switch of the (N + 1) ch system is output. The switch of the (N + 1) ch system responds to this control signal while chattering, and shifts to the value of the (N + 1) ch after the chattering ends. At this time, although the preamplifier U1 and the A / D converter ADC itself have a time constant, the electric charge of the capacitor C is discharged and becomes 0, so that the value of (N + 1) ch is correctly output. The time required can be shortened as compared with FIG. 7.

[0007]

Here, in the case of FIG.
The waiting time can be shortened by narrowing the limit voltage range ± V _lim of the limiter, but one polarity component of the normal mode noise superimposed on the measurement signal is limited and NM
There is a problem that RR (normal mode noise rejection retio) deteriorates.

In addition, in the case of FIG. 8, in addition to turning on the switch SW _d → discharging the capacitor C → turning off the switch SW _d while the switches of all channels are off, a margin time for a safety measure is secured. There is a need. This is because if the switch of the (N + 1) ch system is turned on before the switch SW _d is turned off, the measurement signal system is directly grounded and may be destroyed. That is, in the case of FIG. 7, there is a problem that the entire operation time becomes long and there is a risk that the measurement signal system is destroyed.

The present invention solves these conventional problems, and an object of the present invention is to realize a multipoint measuring device capable of performing high-speed and highly accurate measurement.

[0010]

A multipoint measuring device of the present invention is a multipoint measuring device configured to sequentially and selectively add multipoint measuring signals to an integration type A / D converter to convert them into digital signals. In the point measuring device, a limiter circuit that can switch the input signal level of the A / D converter to a plurality of levels of limit voltage is provided, and the limit voltage range of this limiter circuit is widened at the time of measurement by interlocking with the switching operation of the measurement point. The feature is that it switches narrowly during non-measurement.

[0011]

The input signal level range of the A / D converter is limited by the limiter circuit whose limit voltage range can be switched in association with the switching operation of the measuring points. That is, the limit voltage range of the limiter circuit can be switched wide during measurement and narrow during non-measurement. As a result, the overall waiting time can be shortened and high NMRR can be realized.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of the present invention.
The same reference numerals are given to the same portions as. The difference between FIG. 1 and FIG. 6 is that a limiter circuit for limiting the input signal level of the A / D converter ADC is provided that can switch to a plurality of limit voltage levels, and the limit voltage range of this limiter circuit is set at the measurement point. In conjunction with the switching operation, the switching is wide during measurement and narrow during non-measurement.

That is, in FIG. 1, the limiter circuit on the positive polarity side has a diode D1 whose anode is connected to the input terminal of the A / D converter ADC, and whose output terminal is connected to the cathode of the diode D1 and whose inverting input terminal is An operational amplifier U2 connected to the anode of the diode D1, a resistor R ₁ connected to the non-inverting input terminal of the operational amplifier U2 and the movable contact a of the changeover switch SS1 at one end, and a voltage + V ₁ applied to the other end; Is connected to one fixed contact b of the changeover switch SS1 and the other end is connected to the common potential point, and a resistor R ₂ is connected to one fixed contact c of the changeover switch SS1 and the other end is connected to the common potential point. It is composed of a resistor R ₃ and a resistor R ₃ . The limiter circuit on the negative polarity side
A diode D2 having a cathode connected to the input terminal of the A / D converter ADC, an operational amplifier U3 having an output terminal connected to the anode of the diode D2 and an inverting input terminal connected to the cathode of the diode D2, and a voltage at one end A resistor R to which V _l is applied and whose other end is connected to the non-inverting input terminal of the operational amplifier U3 and the movable contact a of the changeover switch SS2
₆ , a resistor R ₄ having one end connected to one fixed contact b of the changeover switch SS1 and the other end connected to a common potential point, and one end connected to the other fixed contact c of the changeover switch SS2 and the other end common It is composed of a resistor R ₅ connected to a potential point. Here, as the changeover switches SS1 and SS2,
For example, a semiconductor switch having a fast response is used.

The limit voltage of each limiter circuit in such a configuration is switched by the switching state of the changeover switches SS1 and SS2. For example, when the movable contact a of the changeover switch SS1 of the positive polarity side limiter circuit is connected to the fixed contact b side, + R ₂ · V _l / (R ₁ + R ₂ ) and the movable contact a of the changeover switch SS1 becomes Fixed contact c
In the state of being connected to the side, + R ₃ · V _l / (R ₁ + R ₃ ). Similarly, the limit voltage on the negative polarity side is switched depending on the switching state of the movable contact a of the changeover switch SS2.

The operation of FIG. 1 will be described with reference to FIG. Figure 2
Then, in the Nch measurement signal, the saturation region is large on the minus pole side.
It has passed over, and (N + 1) ch gets tired of the plus pole direction.
The case where the value is far from Nch in the sum area is shown.
Nch or (N + 1) ch system switch is on
At this time, the movable contact a of the changeover switches SS1 and SS2 is limited.
The side where the voltage range becomes wider (-VL_W, + VL_W) Fixed connection
It is switched and connected to a point (for example, b), and the switch of all channels is switched.
When the switch is off, the movable contacts of the changeover switches SS1 and SS2
a is the side where the limit voltage range becomes narrower (-VL_N, + V
L_N) Is fixedly connected to the fixed contact (for example, c). Concrete
The switch of all channels is switched off during the off period.
Set the movable contact a of the switches SS1 and SS2 to the limit voltage range.
Side where the enclosure becomes narrower (-VL_N, + VL_N) Fixed contact (eg
If it is connected to c), the system of Nch or (N + 1) ch
After the command switch is turned on and chattering ends
Limit the movable contact a of the changeover switches SS1 and SS2
Wider voltage range (-VL _W, + VL_W) Fixed contact
(For example, b) is switched and connected.

By driving as described above with such a circuit configuration, the limit voltage range is widened during measurement and the NMRR is improved, and the limit voltage range is narrowed during non-measurement, and thus the A / D converter ADC. The transition time of the input signal is shortened and the measurement interval is shortened. That is, the effects of improving the NMRR and shortening the measurement interval, which are not compatible with the conventional circuit configuration, are obtained.

FIG. 3 shows a comparison diagram of the time required for state transition between the conventional circuit configuration and the circuit configuration of the present invention when the same NMRR is intended to be realized. (A) shows the case where the switch SWd is not used in the configuration of FIG. 5, (B) shows the case where the switch SWd is used in the configuration of FIG. 5, and (C) shows the case of the configuration of FIG. . (C) is obviously short in the time from when the switches of all the channels are turned off until the measurement of the (N + 1) channels is started.

FIG. 4 is an equivalent circuit diagram of the limiter circuit on the plus pole side using the idealizing diode. The limit voltage in the circuit configuration of FIG. 4 is voltage + V _u , V _l , resistance R _u ,
It can be changed by changing at least one of R _l . In the embodiment of FIG. 1, which corresponds to switching of the resistance R _u or R _l , for example, as shown in FIG. 5, a resistance series circuit composed of resistances R _u , R _m , and R ₁ is provided, and its divided output voltage is It may be switched, or voltage + V _u
Alternatively, V _l may be switched. The same applies to the negative pole side.

[0019]

As described above, according to the present invention,
It is possible to realize a multi-point measuring device capable of high-speed and highly accurate measurement.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of FIG.

FIG. 3 is a comparison diagram of operating time between the conventional configuration and the configuration of the present invention.

FIG. 4 is an equivalent circuit diagram of a limiter circuit on the positive pole side using an idealized diode.

FIG. 5 is a circuit diagram showing another embodiment of the present invention.

FIG. 6 is a circuit diagram showing an example of a conventional multipoint measuring device.

7 is an explanatory diagram of an example of the operation of FIG.

FIG. 8 is an explanatory diagram of another example of the operation of FIG.

[Explanation of symbols]

SW _{1 to} SW _m switch U1 to U3 operational amplifier D1 to D2 diode ADC A / D converter SS1, SS2 changeover switch C capacitor R1 to R6 resistance

Claims (1)

[Claims] 1. An integral type A for selectively measuring a plurality of measurement signals in sequence.
In a multipoint measuring device configured to convert into a digital signal in addition to an A / D converter, a limiter circuit that can switch the input signal level of the A / D converter to a plurality of limit voltage levels is provided. A multi-point measuring device characterized in that the limit voltage range of is switched widely during measurement and narrowly during non-measurement in conjunction with the switching operation of measurement points.