JPH0315372B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a switching circuit that amplifies a plurality of weak input signals and sequentially outputs them in a time-division manner.

The circuit shown in FIG. 1 is conventionally known as a circuit that amplifies a plurality of weak input signals and then outputs them sequentially in a time-division manner at high speed.

That is, amplifiers A ₁ , A ₂ , ..., An are connected to input terminals T ₁ , T ₂ , ..., Tn, respectively, and high-speed non-contact switches SW are connected to each of the amplifiers A ₁ , A ₂ , ..., An. ₁ , SW ₂ , ..., SWn are connected, and the other ends of each of the non-contact switches SW ₁ , SW ₂ , ..., SWn are connected to the output terminal Tout. These non-contact switches SW ₁ , SW ₂ , . . . , SWn are composed of, for example, semiconductor analog switches, and the switching time thereof is several μs to several ms.

In the conventional example described above, a high-speed non-contact switch is used to switch a large number of input signals in a short time. In addition, if the input level is an analog signal of several μV to several tens of mV, such as a strain detector signal output from a bridge circuit consisting of a strain gauge, noise components for the switching operation of a non-contact switch may be input. In order to prevent errors from being superimposed on the signal, the signal level is raised to the order of several volts using an amplifier before performing high-speed switching.

First, from the control circuit 10, the non-contact switch is
When a switching command signal is sent to SW ₁ , that switch
SW ₁ is turned on, and a switching completion signal is sent to the control circuit 10 at the end of the switching. As a result, the control circuit 10 sends a conversion command signal to the A/D converter 20, and when the A/D converter 20 converts the analog signal related to the input terminal _T1 into a digital signal, a conversion end signal is sent to the control circuit. Sent to 10. Next, the control circuit 10 sends a switching command signal to the switch SW ₂ , and through operations similar to those described above, the analog signal related to the input terminal T ₂ is converted into a digital signal. By repeating this, the analog signal related to the input terminal Tn is converted into a digital signal, and a series of operations of the switching circuit are completed.

However, in the above conventional example, the input terminals T ₁ ,
The same number of amplifiers as T ₂ , ..., Tn are required, and these amplifiers are not only expensive, but also require relatively large space per one, so as the number of input terminals increases, the switching circuit becomes There are problems in that the overall price increases and the space also increases.

On the other hand, high-speed non-contact switches SW ₁ , SW ₂ ,...,
If a mechanical relay such as a reed relay or a so-called contact switch such as a rotary switch is used instead of SWn, the amplifiers A ₁ , A ₂ , ..., An are not required even for weak input signals, and the above problem can be solved. Does not occur.

However, such a contact switch requires a switching time of several ms to several 100 ms, so when it is necessary to sequentially switch input signals from multiple points (for example, about 1000 points), it takes a long time to complete the switching. In addition, although it is possible to avoid using an amplifier, it takes several tens of ms to several 100 ms to accurately A/D convert a weak signal.
This method has the drawback that it takes a long time, making it impossible to measure relatively fast phenomena of, for example, several hundred Hz.

In order to avoid such problems, there is an analog input signal switching device described in Japanese Patent Laid-Open No. 147052/1983.

This conventional analog input signal switching device includes a plurality of first multiplexers into which a plurality of analog input signals are introduced, and each of the multiplexers sequentially switches the plurality of analog input signals to derive one analog signal. The switching cycles of each of the multiplexers are synchronized, and the signal converting means for converting each signal derived from each of the multiplexers by switching, and a second multiplexer having a switching function of deriving one analog signal from the plurality of analog signals in synchronization with the switching cycle of the plurality of first multiplexers.

To explain this in more detail, analog signals introduced from the outside are grouped by each signal level, and passed through the first multiplexer.
The voltage is isolated and amplified by the voltage converter provided for each group, input to the A/D converter via the second multiplexer for each group, and after being digitally converted, it is connected to a computer or digital device. . When data is to be taken in, first, the changeover switches of the same rank in the first multiplexer are closed simultaneously, and after the time constant T of each voltage-to-voltage converter, the changeover switches of the second multiplexer for each group are closed. A/D conversion is carried out by switching the signals in sequence.

However, even after the changeover switches of the second multiplexer for each group are turned on and off sequentially up to the last group, and the changeover switches of the next order in the first multiplexer are closed simultaneously, the time constant T is still After waiting, the second
Since the on/off operation of the multiplexer is started, the above time constant T time is wasted.
In the case of sequentially switching the input signals (on the order of points), it takes a long time that cannot be ignored, which is inconvenient in pursuing as much simultaneity of measurement data as possible.

The present invention was made in view of the above circumstances, and
The objective is to significantly reduce the need for expensive and space-consuming amplifiers by using relatively slow contact switches and high speed non-contact switches, while maintaining the substantially faster switching times of non-contact switches. An object of the present invention is to provide a switching circuit capable of switching each of a large number of input signals.

The present invention is a switching circuit that amplifies a large number of weak input signals and outputs them sequentially in a time-divided manner, in which one contact side of a relatively low-speed contact switch is connected to each input terminal of the switching circuit one by one. , the other contact side of the contact switch is grouped into a plurality of groups and connected to each other, one amplifier is connected to each group, one high-speed non-contact switch is connected to each of the amplifiers, The other sides of the contact switches are connected to each other to serve as output ends of a switching circuit, the switching order is determined for the contact switches in each group, and the contact switches in each group in the first order are switched once in advance. The non-contact switches corresponding to each group are turned on and off sequentially from the first group to the last group within a predetermined time, and the non-contact switches in the corresponding group are turned on in relation to the off operation of the non-contact switches. turning off the contact switch in the first order and turning on the contact switch in the next order;
When the off operation of the non-contact switch corresponding to the last group in the first order is completed, in conjunction with this off operation, the contact switch in the first order in the corresponding last group is turned off, and the switch in the next order is turned off. It has a control circuit that turns on the contact switch and then turns on and off the non-contact switch and the contact switch again from the first group in the next order, the number of groups of contact switches is M, and one contact switch is provided. The time required for the amplified output of the input signal to stabilize after the switch is switched, plus the operating time of the non-contact switch.
The above objective can be completely achieved by setting the operating time T _H of the non-contact switch to satisfy the relational expression T _H ≧T _L /M where T L is T _L .

The present invention will be described in detail below based on embodiments shown in the accompanying drawings.

FIG. 2 is a circuit diagram showing one embodiment of the present invention, and FIG. 3 is a timing chart of the above embodiment.

In the figure, the input terminals of the switching circuit T ₁₁ , T ₁₂ ,...T ₁ n,
…, T ₂ n, … Tmn are relatively low-speed contact switches S ₁₁ , S ₁₂ , …, S ₁ n, …, S ₂ n, …,
It is connected to one contact side of Smn, that is, the movable contact side. And the above contact switches S ₁₁ and S ₁₂
..., S ₁ n..., S ₂ n..., Smn, the other contact side, that is, the fixed contact side, is distributed into m groups, the first switch group SG ₁ , the second switch group
_{SG 2} , .
Connected to AG ₂ , ..., AGm. further amplifier
AG ₁ , AG ₂ , . . . , AGm are connected to one output terminal Tout of the switching circuit via high-speed non-contact switches S ₁ , S ₂ , . . . , Sm, respectively. For example, an A/D converter 20 is connected to this output terminal Tout.

The contact switches S ₁₁ to Smn, the non-contact switches S ₁ to Sm, and the A/D converter 20 are as follows:
They are respectively connected to the control circuit 11, and the switching control of the follower switches and the A/D conversion control are performed in a predetermined order as described below.

Contact switch S ₁₁ ~ S ₁ n, S ₂₁ ~ S ₂ n, Sm ₁ ~
Smn is composed of a mechanical relay such as a reed relay or a rotary switch, and the switching time thereof is about several ms to several 100 ms. The non-contact switches S ₁ to Sm are composed of semiconductor analog switches, etc., and the switching time thereof is several μs to several ms.

Further, each contact switch in each switch group SG ₁ to SGm has a respective switching order. For example, the switching order in switch group SG ₁ is the order of switches S ₁₁ , S ₁₂ . . . S ₁ n, Switching order in switch group SG ₂ is switch
The order is S ₂₁ , S _{22 .} . . , S ₂ n, and so on.

In addition, the non-contact switches S ₁ to Sm provided corresponding to each switch group are sequentially connected from switch S ₁ corresponding to the first group to switch Sm corresponding to the last group, and then sequentially to switch Sm corresponding to the last group. The control circuit 11 sequentially turns on and off at high speed from the switch Sm corresponding to the first group to the switch _S1 corresponding to the first group. Then, in conjunction with the off operation of the non-contact switches S ₁ to Sm, the on-operating contact switches (for example, S ₁₁ ) in the corresponding groups are turned off, and the next-order contact switches (for example, S ₁₂ ) are turned off. ) to turn on the
It is controlled by a control circuit 11. That is, if we pay attention to the state of a contact switch in a certain switching order, the contact switch (for example, S ₁₂ ) in that switching order will turn off the state of the non-contact switch (for example, S ₁ ) in the previous switching order. This means that it has already been turned on. Therefore, since the contact switch only needs to be turned on and off before the high-speed non-contact switch completes one cycle of switch operations for m groups, a relatively slow reed relay or the like can be used. However, this has almost no effect on the switching time in the entire switching circuit. This point will be discussed later.

Note that at the start of switch switching, the first-ranked contact switches S ₁₁ , S ₁₂ , ...Sm ₁ are off, so either turn them on at the same time or turn on the non-contact switches S ₁ to Sm in advance. It is assumed that the contact switches S ₁₁ , S ₁₂ , . . . Sm ₁ are sequentially turned on by turning them on and off from the first group to the last group.

Next, the operation of the above embodiment will be explained.

First, input terminals T ₁₁ ~ Tmn each have 10 mV.
Assume that the following analog input signals are applied. In response to a switching command signal from the control circuit 11, several contact switches S ₁₁ , S ₂₁ , ..., Sm ₁ are activated almost simultaneously.
It is turned on for about 100ms, and each input signal is connected to the amplifier AG ₁ ,
AG ₂ , ..., AGm each amplify it to about several volts. Here, even if weak input signals are switched by each of the contact switches, switching errors that occur when non-contact switches are used do not occur.

Next, near the end of the on time of the contact switch S ₁₁ , the non-contact switch S ₁ is turned on, and as the non-contact switch S ₁ is turned off, the contact switch S ₁₁ is turned off.
As a result, the contact switch _S12 , which is second in switching order in the first switch group _SG1 , is turned on.
Further, when the non-contact switch _S1 is turned off, the non-contact switch _S2 corresponding to the next group is turned on. Thereafter, when the non-contact switch _S2 is turned off, the contact switch _S21 is turned off, the second contact switch _S22 in the switching order is turned on, and the contact switch _S3 is also turned on. By repeating this, the non-contact switch S ₁ ~
When Sm is turned on in sequence and each non-contact switch is turned off, the contact switch in the current switching order in the switch group related to them is turned off, and the contact switch in the next switching order is turned on. In this way, the non-contact switch Sm is turned on. As a result, the input terminals T ₁₁ , T ₂₁ , ..., Tm ₁
The input signals at Tout appear sequentially at the output terminal Tout.

Next, when the non-contact switch Sm is turned off, the non-contact switch S ₁ corresponding to the first group is turned on again, and through the same operation as above, the input terminals T ₁₂ ,
The input signal at T ₂₂ ,..., Tm ₂ is output to the output terminal Tout
appear sequentially. Repeat this until the input terminal
The input signals at T ₁ n, T ₂ n, . . . , Tmn appear at the output terminal Tout, completing the series of switching operations.

Switching control of each switch as indicated by arrows in FIG. 3 is performed by a control circuit 11. To start the switching circuit here, use the contact switch.
It is sufficient to turn on all of S ₁₁ , S ₂₁ , . . . , Sm ₁ and turn on switch S ₁ within the on period of contact switch S ₁₁ .

The conditions for grouping each contact switch include the level of the input signal, the price of the amplifier, the space, the conversion speed of the A/D converter, etc.
In addition to this, it is necessary to satisfy the following formula.

T _H ≧T _L /M where M is the number of groups of contact switches, T _H
is the operating time of a non-contact switch, and is the predetermined signal processing time.For example, the time from when the output of an amplifier is switched by a non-contact switch to the completion of A/D conversion, T _L is 1
This is the time from when one contact switch switches until the amplified output of the input signal becomes stable, plus the operating time of the non-contact switch.

In the second illustrated embodiment configured in this manner, switches S ₁₁ to Smn are connected to each input terminal.
The number of amplifiers can be reduced compared to the conventional method because it is sufficient to group the amplifiers and provide the same number of amplifiers as the number of groups. In the case of the second illustrated embodiment, a switching circuit with the same performance as the conventional circuit can be obtained with 1/n fewer amplifiers than the conventional circuit.

Further, according to the above embodiment, the contact switches S ₁₁ , S ₂₁ , _. After turning on sequentially, the prescribed stabilization time (several 100ms)
However, the contact switches S ₁₂ , S ₂₂ , ..., Sm ₂ in the second and subsequent ranks are turned off immediately after the contact switches S ₁₁ , S ₂₁ , ..., Sm ₁ in the previous order are turned off. is turned on, and by the time the input signal of the relevant rank is switched by the non-contact switches S ₁ to Sm,
The time it takes for the input signals T ₁₁ , T ₂₁ , ..., Tm ₁ of the previous order to go through one round of signal acquisition time at the non-contact switches S ₁ to Sm (the predetermined signal processing time is the operating time of the non-contact switches, For example, the time required to complete A/D conversion after switching the output of an amplifier with a non-contact switch multiplied by the number of groups m) can be effectively used as the stabilization time, so in order to capture the input signal of the relevant rank, There is no need to provide the stabilization time each time, and signals can be switched in substantially the switching time of a high-speed non-contact switch.

Further, in the case of a non-contact switch, noise components due to the switching operation are likely to be superimposed on the weak input signal in the case of a non-contact switch, but in the case of a contact switch as in the above embodiment, this disadvantage does not exist.

As detailed above, according to the present invention, in a switching circuit that amplifies a plurality of weak input signals and then sequentially outputs them in a high-speed time division manner, the input signals are grouped into several groups, and each input signal is is time-divided by a low-speed selector switch and then amplified.
After the amplifier, each input signal is time-divided by a high-speed changeover switch, and in particular, the contact switches in each group in the first order are turned on only once when starting for the first time. After the fixed time, the non-contact switches are used to time-divide sequentially from the first group within a predetermined time, but the contact switches in each group from the next rank onwards are switched off when each contact switch in that rank turns off. Further, the number of groups of contact switches is M, and the operation time of the non-contact switch is defined as the time from when one contact switch is switched until the amplified output of the input signal becomes stable. When the added time is T _L , the operating time T _H of the non-contact switch is set to satisfy the relational expression T _H ≧T _L /M, so the conventional analog input signal described in the above publication is Unlike a switching device, there is no need to take a predetermined time every time data in the last group of each rank is taken in, and the switching time of each input signal is substantially the same as the switching time of a high-speed non-contact switch (for example, If a semiconductor analog switch is used, the switching time will be several microseconds to several milliseconds), and the switching time can be about the same as a conventional switch that has the same number of amplifiers as the number of input signals and a high-speed non-contact switch. The number of switching circuits can be reduced, thus reducing the cost of the entire switching circuit and reducing the size of the switching circuit as a whole.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional switching circuit, FIG. 2 is a circuit diagram showing an embodiment of the present invention, and FIG. 3 is a timing chart of the above embodiment. T ₁₁ ~ Tmn... Input terminal of switching circuit, SG ₁ ~
SGm...Switch group, _S11 ~Smn...Contact switch, _AG1 ~AGm...Amplifier, _S1 ~Sm...
...non-contact switch, Tout...output terminal of switching circuit, 11...control circuit.

Claims (1)

[Claims] 1. In a switching circuit that amplifies and sequentially outputs a large number of weak input signals in a time-division manner, one contact side of a relatively low-speed contact switch is connected to each input terminal of the switching circuit. The other contact side of the contact switch is grouped into multiple groups and connected to each other, one amplifier is connected to each group, and one high-speed non-contact switch is connected to each of the amplifiers. , the other sides of the non-contact switches are connected to each other to serve as output ends of a switching circuit, the contact switches in each group are assigned a switching order, and the contact switches in each group in the first order are set as output terminals of a switching circuit. The non-contact switches corresponding to each group are turned on and off in sequence from the first group to the last group within a predetermined time after being turned on only once in advance, and a response is taken in relation to the off operation of the non-contact switches. The contact switch in the first order in the group is turned off, and the contact switch in the next order is turned on, and when the non-contact switch corresponding to the last group in the first order completes the off operation, the switch is turned off. In association with this, the contact switch in the first order in the corresponding last group is turned off and the contact switch in the next order is turned on, and then the non-contact switch and the contact switch are turned on again from the first group in the next order. It has a control circuit that turns the switches on and off in the same way, and the number of groups of contact switches is M.
The time from when one contact switch is switched until the amplified output of that input signal stabilizes is the sum of the operation time of the non-contact switch.
A switching circuit characterized in that the operating time T _H of the non-contact switch is set so as to satisfy the relational expression T _H ≧T _{L /} M, where T L is T L.