JPS6075999A - Analog input unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a transformer-insulated analog input device that has a thermocouple disconnection detection function and that inputs a thermocouple input via a Cruz transformer.

[Technical background of Departure]

Generally, this type of analog input device is constructed as shown in FIG. Thermocouples TCI to TCn constitute one group. Any thermocouple T in this group
Ci (i is one of 1 to n) is a point switch S that operates in response to a scan request from the controller 11.
1i.

5211 group switch S3. However, noise is generated in the thermocouple TC1, and noise removal filter F
The thermocouple input from which noise has been removed is supplied to an amplifier (hereinafter referred to as Amp) 12 via a point switch SJi, a transformer T1, a point switch S2i, and a group switch S3f. This Amp 1
The amplification method for step 2 is an analog/digital converter (hereinafter referred to as A).
(referred to as DC) 13, the A/D is converted into 9A/D.
'D conversion data (digital digital data) is controller 1
1.

By the way, this type of analog input device W is provided with an isolated power generation circuit CKTi that applies an isolated power supply to the thermocouple TCi (+=1 to n), as shown in FIG. Insulated power generation circuit CKTi (thermocouple TCI in Figure 1)
(detailed diagram is shown only for the circuit corresponding to the controller 11)
It is turned 0N10FF by the common control signal 14 from .

In addition, the isolated power supply generation circuit CKTi (1=1 to n) (
7) The reason why the 0N10FF control is performed not for all points but for each group is because the scan speed of the transformer-insulated analog input device shown in FIG. 1 is a diagonal speed (several tens of microseconds). Here, the isolated power supply generating circuit CKT1 will be explained.

The isolated power supply generation circuit CKT7 is provided with a drive circuit DI and an i+ transformer T21.

The drive circuit D applies a pulse voltage to the pulse transformer T21 in response to the control signal 14 from the controller 11. As a result, an insulation voltage ell is generated from the Kp4 transformer T21 as shown in the timing chart of FIG. This insulated voltage ell is divided according to the ratio of the impedance of the thermocouple TCI to the output impedance of the insulated power supply circuit CKT1, and the outside of the divided voltage is applied to the noise removal filter F1. This applied voltage e21 is applied when the thermocouple TCI is disconnected. In the normal state where no pressure is applied, the ηL pressure is low as shown by the solid line in FIG. On the other hand, thermocouple TCI
When the wire is disconnected, the voltage becomes high as shown by the broken line in FIG. Therefore, if a scan request specifying the thermocouple TCI input is issued in this state, the ADC 13
/D conversion data will overflow. In addition, thermocouple T
If C1 is normal, overflow will not occur, but
Since the isolated power supply is applied from the isolated power supply circuit CKT1, the A/D conversion data is higher than the true value.

[Problems with back piercing technology]

This J: In the conventional analog input device, heat 'fiI
When the insulated power supply for detecting disconnection of the pair is ONL, the input value of the thermocouple becomes higher than the direct value, so there is a drawback that accurate temperature measurement cannot be performed. In order to solve this drawback, it may be possible to turn off the insulated power supply and then perform the temperature side W (scan request). However, with the method of measuring temperature after turning off all insulated power supplies, the voltage stored in the noise removal filter and stray I gear/exiter by the cable between the thermocouple and the thermocouple becomes the thermocouple's output voltage itself. The drawback was that it took a long time to complete the process, making it difficult to use heavy manual labor.

[of the invention]

This research r1 was made in view of the above circumstances, and its purpose is to provide an analog input device that can detect thermocouple disconnection during scanning and that can perform correct analog input.

[Summary of the invention]

In this invention, in the analog input device that inputs a thermocouple input applied to a noise removal filter via a first Nors transformer in response to a scan request from a controller, the thermocouple input is applied to the filter. A first semiconductor switch is provided for inhibiting during all of the above scanning requests (ie, during temperature measurements of specified Δ? India).

1- Therefore, in the present invention, the thermocouple input stored in the noise removal filter (the capacitor therein) before the scan request is input in response to the scan request. 1. In this invention, there is a drive circuit that generates positive and negative pulses 'tjL pressure, a second pulse transformer that is driven by this drive circuit and applies positive and negative voltages to the thermocouple, and a third A second semiconductor switch is provided which forms a blood flow route f-2 consisting of these thermocouples and the second and third i4 transformers during a scan request. The output of the pulse transformer of the feeder 3 is amplified by a comparison circuit and compared with a reference voltage. The comparison result of this comparison circuit indicates whether or not the thermocouple is disconnected.

[Embodiments of the invention]

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 3 and 4. Note that parts that are the same as those in FIG.

In the analog input device shown in FIG.
The semiconductor switch (first semiconductor switch) indicated by S4n is a switch that completely prohibits/allows the thermocouples TCI to TCn inputs to be applied to the noise removal filters F1 to Fn. Semiconductor switch 84 i (+= 1 to n
) is turned off under the control of the controller 2 when a disconnection of the corresponding thermocouple TCi is detected. It's a reed, code CKT 1
The disconnection detection circuits indicated by 1 to CKT 1 n are circuits that output voltages e41 to 84n'i corresponding to (inversely proportional to) the impedances of the thermocouples TCI to TCn. These disconnection detection circuits CKT 11 to CKT 1 n correspond to thermocouples TCI to TCn under the control of the controller 2.
It is selectively driven depending on the scan. Output voltage e41~ of these disconnection detection circuits CKT11~CKT1n
e4n is supplied to Amp (amplifier) 22. Amp
The amplified output e5 of 22 is a comparator (the following results are thermocouple TC
It is led to the controller 2 as a disconnection detection circuit (binary decoding) 24 that indicates the presence or absence of disconnection of i.

Next, the internal configuration of the disconnection detection circuits CKT I 1 to CKT 1 n will be explained by taking the disconnection detection circuit CKT IJ as an example. In addition, in this embodiment, the disconnection detection circuit C
The internal configurations of KT 71 to CKT n are basically the same. In the disconnection detection circuit CKT 11, the drive circuit indicated by the symbol Dll is positive in response to the control signal CNT I J from the controller 21.

A negative pulse voltage e31f is generated.

This pulse voltage e 31yyrus transformer (second) f
transformer) is applied to the primary side of T31. The secondary side (secondary winding) of the pulse transformer T31 is inserted between one end of the thermocouple TCI and the semiconductor switch 841 PC'. There is a pulse transformer (No. 30) between the common connection point between the secondary winding of the transformer T31 and the semiconductor switch 541 (one end) and the other end of the thermocouple TCI. Transformer) T41 secondary winding and semiconductor switch 851
(second semiconductor switch) is inserted. The semiconductor switch S5'l is the semiconductor switch S
An optical switch S61'f is configured together with a photodiode PDI which is 0N10FF.

Photodiode PDI is driven by transistor Q1. This transistor Ql (d is controlled by the controller 21 and is driven by several columns of CNTs 27).The secondary side 141 power e41 of the pulse transformer T41 is supplied to the Amp 22 via the semiconductor switch 571f.

Next, the operation of the configuration shown in FIG. 3 will be explained with reference to the timing chart shown in FIG. Assume that the thermocouple TCI is not currently the subject of a scan request. In this case, the controller 2) fljlJ controls the number? india switch 8
11. S21 is in the OFF state, and the semiconductor switch s4
1 is in the ON state. Good luck, semiconductor switch s51 is O.
It is in FF state. In this state, the ground Ff'Jd generated by the thermocouple TCJ is applied to the noise removal filter F1 via the switch 541f, and is stored in the filter Fl (the capacitor therein). Then, a scan request is issued to the controller 21 for the thermocouple T C1, and the month? Into switch f811, 821 group switch S3
is turned on, and at the same time, the semiconductor switch S41 is turned off. This is the noise removal filter li' 1
The output of the thermocouple Tc1 stored in the capacitor (inner capacitor) is supplied to Arnp 12 via switch S11, pulse transformer (first pulse transformer) T11, switch S21, and switch S3. This Amp12
The amplified output of ADCI, ? Yo! 11 A/D conversion is performed, and the A/D conversion data is supplied to the =1 controller 21. In this case, the pulse voltage applied to the thermocouple TCI by the pulse transformer T31 (in the disconnection detection circuit CKT 11) is prohibited from being applied to the filter F by the switch 541 (turned OFF). be done.

Therefore, with the analog human-powered device shown in FIG. 3, accurate thermocouple power (temperature measurement) can be achieved without being affected by disconnection detection, which will be described later.

The controller 21 turns the switch 4J-z OFF (switch S
ll, 821) and at the same time the control signal CNT
21, CNT 11 all output. This drives the transistor Ql and the drive circuit Dll. When the transistor Q1 is driven, the optical switch 861 (semiconductor switch 551),
A current loop consisting of the pulse transformer T41 (01st order winding) is formed. In addition, the drive circuit Dll is
By being controlled by the control signal CNT 11, negative and positive pulse voltages 03 are generated as shown in FIG. This pulse voltage eai is no! It is applied to the primary side of the transformer T31. As a result, a voltage corresponding to the Norse voltage e31 is generated on the secondary side of the pulse transformer T31, and a loop current inversely proportional to the impedance of the thermocouple TC1 flows in the above-mentioned loose current.

As a result, the roof'' is placed on the secondary side of the pulse transformer T41.
A voltage e41 proportional to the current is generated.

Controller 2 has transistor Q1 and drive circuit D.
At the same time as driving ll, semiconductor switch 871 is turned on. Therefore, the voltage e41 generated on the secondary side of the Noculus transformer T41 is transferred to Arn via the switch S71.
Supplied on p 22. Amp 22 amplifies voltage e41 with a predetermined gain. COMP23 compares the amplified output voltage e5 of the Amp 22 with the reference voltage □2. C
OMP 23 is logic “o” when e5>■Rwy
When e5≦vREF, a disconnection detection signal 24 of logic “1” is output. thermocouple TC
If I is disconnected, the loop current will not flow. Therefore, the secondary output voltage e of the pulse transformer T41
41 becomes Ov as shown by the broken line in Figure 4, and Amp
The output 'voltage e5 of 22 is also lower than the reference voltage V□, as shown by the broken line in FIG. Therefore, COMP
The output (wire breakage detection signal) 24 of 23 becomes a pot break °'1'' (indicating a wire breakage) as shown by the broken line in FIG. It is possible to determine if the thermocouple TCJ is disconnected.In this example, all negative and positive pressures are used for the delicate output of the thermoelectric lamp TC1.For this reason, the disconnection The pressure applied to the thermocouple TCZ at the end of detection can be set to Ov.
is ON 71 (at this time switch 811.821.8
61 is OIi''Fs1+, ru), a correct thermocouple TC1 input that is not affected by disconnection detection is applied to the noise removal filter F.

〔Effect of the invention〕

As described in detail above, according to the present invention, disconnection of a thermocouple can be detected during scanning. Furthermore, correct thermocouple input (temperature measurement) is possible without being affected by disconnection detection. Furthermore, since disconnection of the thermocouple can be detected during scanning, there is no problem with high-speed input. Furthermore, for the same reason, control is performed only by PBJ compared to a method in which scanning and disconnection detection are performed at different timings.

4 Simple Ma of drawings? , Figure 1 is a diagram showing the configuration of a conventional analog input device FIG. 4 is a timing chart for explaining the operation of the analog input device according to the example.

13...Analog/7' innotal converter (ADC),
2: Controller, 23: Comparator (COMP
), Fl~Fn...Noise removal filter, TC1~T
Cn-thermocouple, T71=TZn, T31, T41・
= /f # Strans, 841~S4n, S51°S 7 J...Semiconductor switch, CKT11~CK
T1n...Disconnection detection circuit, D11-DJn...Drive circuit.

Claims (1)

[Claims] In the analog input device d, which inputs the thermocouple input applied to the noise removal filter via the first pulse transformer in response to the scan request from the controller, during the scan request, the corresponding thermocouple input is input to the filter. a first half-uniform six-body switch that stops the voltage applied to the
The heat 'rlJ: the second) applying a pulse voltage to the pair
a drive circuit that drives the second pulse transformer so that positive and negative /P pulse voltages are applied from the second pulse transformer to the thermocouple and the second pulse transformer; A third pulse transformer dissipates a part of the loose current passing through the second pulse transformer; amplifying the output of the semiconductor switch and the third pulse transformer,
An analog input device characterized in that it is completely equipped with a comparator circuit that compares it with a reference voltage and outputs a binary signal indicating whether or not the corresponding thermocouple is disconnected.