JPH0720166A - Input device - Google Patents

Abstract

PURPOSE:To provide an input device wherein a latching operation can be performed with high accuracy without being effected by a residual voltage. CONSTITUTION:Signals which are latched by measuring input switches S1, S2,...Sn and a zero-input switch So for an input changeover device 1 are amplified by an amplifier 3 via a filter circuit 2, digitized by an A-D converter 4, and subjected to a prescribed processing operation in a processing means 5. Then, the zero-input switch So for zero cancellation is set to ON until a next channel is latched after finishing the prescribed operation of the A-D converter 4, and a residual voltage in the filter circuit 2 is eliminated during this period.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an input device for switching and selecting analog measurement input signals.

[0002]

2. Description of the Related Art In a device that takes in and processes an input signal, an amplifier is used to amplify the signal through a filter circuit including a noise removing resistor R and a capacitor C.

[0003]

As described above, since the filter circuit exists, the residual voltage captured last time is superimposed at the time of the next capture, which has a problem that the capture accuracy is affected. Especially, when the input is opened at the time of switching, the influence was great.

SUMMARY OF THE INVENTION In view of the above points, an object of the present invention is to provide an input device which is not affected by a residual voltage and which enables highly accurate acquisition.

[0005]

SUMMARY OF THE INVENTION The present invention provides an input selector for switching between a measurement input switch and a zero input switch to receive a measurement input signal or a zero input signal, and an output of the input selector via a filter circuit. An amplifier that amplifies, and A that converts the output of this amplifier into a digital signal
The -D converter and the processing means for turning on the zero input switch until the predetermined operation of the A-D converter is completed and the next measurement input switch of the input selector is turned on. It is an input device.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a structural explanatory view showing an embodiment of the present invention.

In the figure, 1 is the measurement input terminals t1, t
2, ..., Tn supplied with the measurement input signals e1, e2,
..., measurement input switches S1 and S for switching and selecting en
, 3, Sn, and an input selector 3, which includes a zero input switch So for selecting the zero input terminal to which is short-circuited and is connected to the ground to which the zero input signal is supplied. An amplifier, such as a variable gain amplifier, which inputs through a filter circuit 2 including a resistor R and a capacitor C and amplifies the signal by a predetermined number, 4 is an AD converter for converting the output of the amplifier 3 into a digital signal, and 5 is A A microcomputer, a CPU or the like that takes in the output of the -D converter 4 and performs a predetermined process, and controls the input of the input selector 1, the amplification degree of the amplifier 3, the timing of the AD converter 4, and the like. It is a processing means.

That is, normally, when the measurement input switches S1, S2, ..., Sn of the input switch 1 are sequentially turned on, they are taken in, amplified by the amplifier 3, and converted into a digital signal by the AD converter 4. The difference between the signal D and the zero signal Z when the zero input switch So is turned on is taken by the processing means 5,
The drift and the like caused by the amplifier 3 and the like are removed.
The amplification degree A and the drift amount A of the amplifier 3 are set to, for example, the first
The following equation holds for the channel.

D = A (e1 + A) (1) Z = A (eo + A) = AA (2) When the subtraction process is performed for (1) and (2), the output E1 becomes the following expression.

E1 = D−Z = A (e1 + Δ) −AΔ = Ae1 (3) In this way, the drift component is removed. in this case,
If there is a residual voltage ΔE in the measurement of the previous channel for a specific channel, this amount will be added to the measurement of the next channel, and it will be difficult to cancel by the above method.
Therefore, the zero input switch So is used as follows.

As shown in the operation explanatory view of FIG. 2, the switches S1, S2 ,.
1, e2, ..., En, and eo are fetched, but the operation timing of the processing means 5 and the like is as follows.

(1) The measurement input switches S1 ... Are sequentially turned on.

(2) Required gain of the amplifier 3 (amplification degree)
To set.

(3) The conversion of the AD converter 4 is started.

(4) The conversion of the AD converter 4 is completed.

(5) The processing device 5 takes in the conversion result of the AD converter 4.

(6) From the end of the predetermined conversion operation of the AD converter 4 until the next measurement input switch is turned on, the zero input switch So is turned on to discharge the residual voltage of the filter circuit 2. Set to zero.

(7) The next measurement input switch is turned on again, and the operation is repeated.

(8) After the end of taking in each measurement channel or all measurement channels S1 ..., Sn, the A / D conversion is started with the zero input switch So kept on, and when the processing is completed, the zero input is performed by the processor 4. The data is stored in the fetch memory and the drift removal calculation is performed.

(9) The measurement input switch S1 is turned on again, and the above operation is repeated.

As described above, since no special switch is required, the zero input switch So for zero cancellation at the time of switching is also turned on, and the residual voltage remaining when it is open is discharged to zero. There is no mutual interference of data, and high-precision measurement is possible. Further, since it is performed together with the drift compensation of the equation (3), it is possible to perform the measurement with higher accuracy.

FIG. 3 shows another embodiment. In this case, A
As the −D converter 4, a double integration type AD converter that performs reference voltage integration after input integration is used. As is apparent from the operation explanatory view of FIG. 3, the zero input switch So is turned on after the predetermined operation of the input integration is completed and before the acquisition of the next channel is selected as compared with FIG. For this reason, the discharge time can be long, the accuracy thereof is high, and the influence of noise is small.

[0023]

As described above, from the end of a predetermined operation of the A / D converter to the acquisition of the next channel, the zero input switch for zero cancellation is also used to turn on the residual voltage of the filter circuit. Since it is eliminated, the circuit drift of the amplifier can be removed, the input does not open, and the influence of the residual voltage of the filter circuit can be removed.
It is possible to reduce the number without increasing the number of parts, and it is possible to capture and measure with higher accuracy.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an embodiment of the present invention.

FIG. 2 is an operation explanatory diagram showing an embodiment of the present invention.

FIG. 3 is an operation explanatory diagram showing an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input selector 2 Filter circuit 3 Amplifier 4 AD converter 5 Processing means S1-Sn Measurement input switch So Zero input switch

Claims (1)

[Claims] 1. An input selector which switches between a measurement input switch and a zero input switch to take in a measurement input signal or a zero input signal, an amplifier which inputs and amplifies the output of this input selector through a filter circuit, and an amplifier of this amplifier. The A / D converter that converts the output into a digital signal and the zero input switch is turned on until the predetermined operation of the A / D converter is completed and the next measurement input switch of the input switch is turned on. An input device comprising a processing means.