JPH0661813A - Analog measurement circuit - Google Patents

Abstract

PURPOSE:To attain a higher speed operation than that of a mechanical relay switch section, a long service life and ease of maintenance by employing a semiconductor switch section for the circuit in place of the mechanical relay switch section. CONSTITUTION:Semiconductor switch sections 7a, 7b are bidirectional to send an analog signal without distortion. Then two semiconductor switches SA, SB of MOS-FET configuration in interlocking with each other are provided to isolate the switch sections from switch drive sections 8a, 8b,.... A buffer amplifier 9 and an A/D converter 10 form an input circuit section for fetching a signal. The semiconductor switches SA, SB have respectively fixed terminals alpha, beta and a switching terminal gamma and their operating service life is semi- permanent to offer the improved reliability and ease of maintenance. Furthermore, the operating speed is faster than that of a mechanical relay switch in the order of two digits or over, the scanning speed of input fetch is increased and the cost is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flying capacitor type analog measuring circuit for a remote monitoring and control device.

[0002]

2. Description of the Related Art Conventionally, this type of analog measuring circuit has been constructed as shown in FIG. 2 by using a mechanical relay switch unit such as a mercury relay switch unit for switching connection of a signal storage capacitor of each channel. . In the figure, 1
a, 1b, ... are various sensors 2a, 2 for outputting analog signals (voltage signals) such as pressure sensors provided in various places in the facility.
Reference numerals b, ... Denote capacitors provided for each sensor 1a, 1b ,.

3a, 3b, ... Are capacitors 2a, 2b ,.
A mercury relay switch section provided for each of the two mercury switch switches Sa and S that are interlocked and switched.
It consists of b. 4a, 4b, ... Are switch sections 3a, 3b,
A relay drive unit provided for each of the ..., 5 is an isolation amplifier for an input buffer, and 6 is an A / D converter for converting an analog signal into digital data.

In the mercury relay switch Sa, the fixed contacts a and b have ends of the sensors 1a, 1b, ...
Is connected to the non-inverting input terminal (+) and the transfer contact c is connected to one end of the capacitors 2a, 2b, .... Further, in the mercury relay switch Sb, the fixed contacts a and b are connected to the other ends of the sensors 1a, 1b, ... And the inverting input terminal (−) of the insulating amplifier 5, and the transfer contact c is the other end of the capacitors 2a, 2b ,. It is connected to the.

When the mercury relay switches Sa, Sb are not driven by the relay drive units 4a, 4b, ..., The transfer contact c is connected to the fixed contact a on the sensor side when not driven. At this time, as is apparent from FIG. 2, the capacitors 2a, 2b, ... Are connected to the sensors 1a, 1b, ... And are charged by the analog signals of the respective sensors 1a, 1b ,. .

On the other hand, the relay drive units 4a, 4b, ... Operate sequentially for each scanning period in synchronization with the scanning for signal acquisition of each channel. By this operation, the switch parts 3a, 3b, ... Are driven in order from the switch part 3a, for example, and the transfer contacts c of the mercury relay switches Sa, Sb are interlocked and switched to the fixed contacts b on the amplifier side.

Therefore, the capacitor 2 of each channel
are sequentially separated from the sensors 1a, 1b, ... For the respective scanning periods and connected to the isolation amplifier 5, and the charging voltage thereof is taken into the isolation amplifier 5. Further, the output voltage of the isolation amplifier 5 based on the charging voltage of the capacitors 2a, 2b, ... Is converted into digital data by the A / D converter 6 in order to facilitate the measurement process in the subsequent circuit section.

Further, when the scanning period of each channel ends, the driving of the switch portions 3a, 3b, ... Stops, and the transfer contact c of each mercury relay switch Sa, Sb is switched to the fixed contact a on the sensor side again. .

Then, by repeating the above-mentioned operations,
The analog signal of each sensor 1a, 1b, ... Is periodically taken into the analog measuring circuit by the scanning method. By the way,
1 indicates an electrical insulation (isolation) line, and conventionally, an insulating amplifier 5 is used to connect the switch parts 3a, 3b, ... On the sensor side of the line 1 and the A / D converter 6 on the circuit side. Is electrically isolated.

[0010]

In the case of the conventional analog measuring circuit described above, a mechanical relay such as a mercury relay switch section 3a, 3b, ... Is used for taking in the analog signal of each channel accumulated in the capacitors 2a, 2b ,. Since the switch is used, it takes 3 to 5 msec to restore the relay operation.
It takes a certain amount of time, and this return time restricts the scanning cycle to limit the analog signal acquisition interval of each channel, and the data conversion cycle of each channel of the A / D converter 6 becomes about 6 to 10 msec. There is a problem in that it becomes long and the so-called input time resolution cannot be improved.

Mechanical relay switches such as mercury relay switches Sa and Sb of the switch portions 3a, 3b, ...
Since the mechanical operation is repeated, the operating life is short, the life cannot be extended, and complicated maintenance is required. Furthermore, expensive mercury relay switches Sa and Sb
There is also a problem that the entire circuit is expensive because it requires mechanical switches such as.

In addition, the mercury relay switch parts 3a, 3
When using b, ..., it is necessary to consider the signal polarity,
Moreover, there is a problem that it cannot be used below the melting point of mercury (−38 ° C.). It is an object of the present invention to improve the time resolution of input, extend the life, and reduce the price, enable use in a low temperature environment, and improve the performance and reliability with a cheaper configuration than before. .

[0013]

In order to achieve the above-mentioned object, in the analog measuring circuit of the present invention, each capacitor for signal storage is connected to each sensor to be monitored when not driven, and each capacitor is connected. A plurality of bidirectional semiconductor switch parts that are charged by the analog signals of the respective sensors, and are electrically insulated from the respective semiconductor switch parts, and sequentially drive the respective semiconductor switch parts in synchronization with the signal reading scan of each capacitor. , A switch drive unit for each semiconductor switch unit, which is sequentially disconnected from each sensor for each scanning period and connected to an input circuit unit for signal reading.

[0014]

In the case of the analog measuring circuit of the present invention configured as described above, the semiconductor switch section is used instead of the conventional mechanical relay switch section such as the mercury relay switch section to switch the connection of the capacitors of the respective channels. Be seen. At this time, since the semiconductor switch part has no mechanical operation part,
It operates remarkably faster than the mechanical relay switch section, and is semi-permanent, and the scanning cycle for capturing the analog signal of each channel is remarkably shortened and the service life is extended.

Further, it can be used even in a low temperature condition where mechanical operation is difficult. Further, since the semiconductor switch portion is bidirectional, it can be easily formed without considering the signal polarity as in the case of using the mercury relay switch portion.

Moreover, the semiconductor switch section is cheaper than the mechanical relay switch section such as the mercury relay switch section,
Moreover, since each semiconductor switch part and the switch drive part are electrically insulated, a special insulating circuit is not required and the device can be formed at low cost. Therefore, the performance and reliability are dramatically improved with a configuration that is cheaper than the conventional one.

[0017]

EXAMPLE One example will be described with reference to FIG. In FIG. 1, the same symbols as those in FIG. 2 indicate the same things, and 7a, 7b, ... Show switch parts 3a, 3b ,.
Is a semiconductor switch portion provided in place of, and has bidirectionality for transmitting an analog signal without distortion and is insulated from the switch driving portions 8a, 8b, ... Individual semiconductor switches SA and SB are provided instead of the switches Sa and Sb in FIG.

Reference numeral 9 is a normal buffer amplifier for an input buffer provided in place of the isolation amplifier 5 in FIG. 10, 10 is an A / D converter equivalent to the A / D converter 6 in FIG. 2, and 11 is A / D.
It is an insulating photocoupler provided on the output side of the D converter 10, and forms an input circuit unit for signal acquisition together with the buffer amplifier 9 and the A / D converter 10. Reference numeral 12 denotes switch drive units 8a, 8b on the circuit side (inside) of the insulation line L.
..., a power supply terminal for supplying + 5V internal drive power supply to the photocoupler 11 and the like, 13 is a DC-DC converter for external power supply, and is + 5V, ± isolated from this power supply based on the internal drive power supply of the power supply terminal 12. An external drive power supply of 15 V is formed to supply power to the sensor side (outside) circuit from the insulation line L of the amplifier 9, the converter 10, and the like.

The semiconductor switches SA and SB are shown in FIG.
The fixed contacts α, β and the switching terminal γ, which are equivalent to the fixed contacts a, b and the transfer contact c, are provided and have the following characteristics 1 to 3 superior to the mechanical switches such as the conventional mercury relay switches Sa and Sb. It has a semi-permanent operating life, improves reliability and is easy to maintain. The operating speed is more than two digits higher than that of the mercury relay switch, and the scanning speed for inputting can be increased. Since it is bidirectional, it is not necessary to consider the directionality in use. It can also be used in low temperature environments below the melting point of mercury (-38 ° C). Cheaper than a mercury relay switch.

Further, by utilizing the above characteristics, the drive unit 8
When the analog signal of each channel accumulated and held in each capacitor 2a, 2b, ... Is fetched by sequentially driving each switch section 7a, 7b ,. It is made sufficiently shorter to greatly improve the time resolution of input. Further, the switch sections 7a, 7b, ... Are electrically insulated from the drive sections 8a, 8b ,.

In this embodiment, electrical insulation between the sensor side and the input side is realized by providing an inexpensive photo coupler 11 after the A / D converter 10 instead of the conventional expensive isolation amplifier 5. To do. As a result, the disadvantages of conventional circuits that use mechanical relay switches, such as mercury relay switches, have been eliminated, and the configuration is cheaper than before, resulting in significantly improved performance, long life, high reliability, and easy maintenance of analog. A measurement circuit can be provided.

[0022]

Since the present invention is configured as described above, it has the following effects. A bidirectional semiconductor switch portion 7a, 7b, ... Is used in place of a conventional mechanical relay switch portion such as a mercury relay switch portion, and each semiconductor switch portion 7a, 7b ,. Since the driving is performed by the driving units 8a, 8b, ..., The scanning period for capturing the analog signal of each channel accumulated in the capacitors 2a, 2b ,.

Further, each semiconductor switch section 7a, 7b, ...
Since it is semi-permanent, it has a long service life and can be easily maintained. Further, each semiconductor switch section 7a, 7b, ...
Is cheaper than the mechanical relay switch section and can be formed at a lower cost than the conventional one.

Moreover, each semiconductor switch section 7a, 7b,
Since .. has bidirectionality, it can be formed without considering the signal polarity. Moreover, it can be used in a lower temperature environment than the conventional device. Therefore, it is possible to provide a novel flying-capacitor-type analog measurement circuit having a semiconductor switch configuration with dramatically improved performance and reliability.

[Brief description of drawings]

FIG. 1 is a connection diagram of an analog measuring circuit according to an embodiment of the present invention.

FIG. 2 is a wiring diagram of a conventional circuit.

[Explanation of symbols]

 1a, 1b Sensors 2a, 2b Capacitors for signal storage 7a, 7b Semiconductor switch section 8a, 8b Switch drive section

Claims (1)

[Claims] 1. In a flying-capacitor type analog measurement circuit of a remote monitoring and control device, each capacitor for signal storage when not driven is connected to each sensor to be monitored, and each capacitor is connected to an analog signal of each sensor. And a plurality of bidirectional semiconductor switch parts that are electrically charged by each of the semiconductor switch parts and are electrically insulated from the semiconductor switch parts. The semiconductor switch parts are sequentially driven in synchronization with the signal reading scan of the capacitors. An analog measuring circuit, comprising: a switch driving section for each semiconductor switch section, which sequentially disconnects a capacitor from each sensor for each scanning period and connects the input circuit section for signal reading.