JPH0553657A - Electronic temperature controller - Google Patents

Abstract

PURPOSE:To provide an electronic temperature controller which fetches the A/D converted input and can improve the influence of the induced noises without requiring a case where a user sets an A/D conversion cycle with a switch in accordance with the power supply frequency. CONSTITUTION:The variance of the mean value of the A/D conversion 3 applied to the input received from a temperature sensor 2 synchronously with 50Hz is compared with the variance of the mean value of the A/D conversion 3 applied to the input of the sensor 2 synchronously with 60Hz. Thus a deciding means 7 decides the frequency of a commercial power supply based on the result of the preceding comparison. Therefore a user is not required to operate a switch for setting the cycle of the A/D conversion 3 in accordance with the power supply frequency since the frequency of the commercial power supply is automatically set. Thus, no setting mistake is produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic temperature controller, and more specifically, to improve the influence of inductive noise received from a commercial power source in synchronization with the power source frequency, the input from the temperature sensor is changed to the power source frequency. A / D at synchronized cycle
The present invention relates to an electronic temperature controller that is converted and captured.

[0002]

2. Description of the Related Art Generally, in an electronic temperature controller, the controllability thereof is often affected by inductive noise received by an input temperature sensor.

For example, as shown in FIG. 3, a molding machine 1
When the temperature control of the band heater 12 wound around the 0 cylinder 11 is performed by the electronic temperature controller 13,
The cylinder 11 is often affected by the commercial power supply, and as shown in FIG. 4, common mode noise (noise between the ground) is generated in the temperature sensor 14, and the temperature sensor 14 If the input impedance of the electronic temperature controller 13 with respect to each of the plus and minus terminals is different, normal mode noise (noise between plus and minus lines) is generated and affects the electronic temperature controller 13. ..

[0004]

In order to reduce the induction noise due to such a commercial power source, it is conceivable to insert a CR filter in the input section from the temperature sensor 14 as shown in FIG. However, in order to obtain a sufficient effect, a considerable time constant is required, and there is a drawback that the speed cannot be increased.

In order to solve such a problem, the input from the temperature sensor 14 is changed to a commercial power frequency (50 Hz /
There is a system for A / D conversion in synchronization with 60 Hz). In this system, for example, as shown in FIG. 6, an input affected by inductive noise is A / D-converted in a cycle synchronized with the commercial power supply frequency, and several times within one cycle T of the commercial power supply. The effect of induced noise is eliminated by performing conversion (six times as indicated by Δ in the figure) and taking the arithmetic mean thereof.

However, in this method, if the A / D conversion cycle is not synchronized with the power supply frequency, the value of the arithmetic mean will fluctuate periodically.

Therefore, in this method, the user operates the switch provided in the electronic temperature controller in accordance with the frequency of the commercial power source used to set the A / D conversion cycle to five.
It is necessary to set the cycle corresponding to 0 Hz or 60 Hz, which is cumbersome, and there is a drawback that a setting error may occur.

The present invention has been made in view of the above points, and provides an electronic temperature controller capable of improving the influence of induced noise without requiring setting according to the commercial power supply frequency. The purpose is to do.

[0009]

In order to achieve the above object, the present invention is configured as follows.

That is, according to the present invention, in an electronic temperature controller including an A / D converter for A / D converting an input from a temperature sensor, an input from a temperature sensor is A / D converted at a cycle synchronized with 50 Hz. A discrimination means for discriminating the commercial power supply frequency is obtained by comparing the fluctuation of the average value of the converted values at this time with the fluctuation of the average value of the converted values when the input is A / D converted in a cycle synchronized with 60 Hz. The input from the temperature sensor is A / D converted in a cycle synchronized with the commercial power supply frequency determined by the determination means.

[0011]

According to the above structure, A / D conversion is performed at a period corresponding to 50 Hz and 60 Hz, and fluctuations in average conversion values are compared to determine whether the commercial power supply frequency is 50 Hz or 60 Hz. Therefore, unlike the conventional example, the user does not need to set the A / D conversion cycle corresponding to the power supply frequency.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an electronic temperature controller according to an embodiment of the present invention.

The electronic temperature controller 1 of this embodiment includes an A / D converter 3 for A / D converting the input from the temperature sensor 2.
A setting unit 4 for setting the target temperature, a display unit 5 for displaying the current temperature detected by the temperature sensor 2 and the target temperature set by the setting unit 4, and whether or not the current temperature has reached the target temperature. It is provided with a microcomputer 7 that determines whether or not to give a corresponding control output to the output unit 6 and controls each unit.

In this embodiment, in order to eliminate the influence of inductive noise from the commercial power source, the input from the temperature sensor 2 is A / D converted and taken in at a cycle synchronized with the commercial power source frequency. In order to eliminate the need to set the cycle of A / D conversion with a switch as in the conventional case depending on whether the commercial power supply frequency is 50 Hz or 60 Hz, the following configuration is adopted.

That is, in this embodiment, the temperature sensor 2
At the time of A / D conversion of the input from the, the average value of the converted values fluctuates unless the A / D conversion is performed in a cycle synchronized with the power supply frequency, and a micro controller having a function as a discriminating means. The computer 7 synchronizes the input with the variation of the average value of the converted values when the input from the temperature sensor 2 is A / D converted in a cycle synchronized with 50 Hz and the input with 60 Hz in the initial operation when the power is turned on. The commercial power supply frequency is discriminated by comparing the fluctuation of the average value of the converted value when A / D conversion is performed in a cycle, and thereafter, the input from the temperature sensor 2 is performed in a cycle synchronized with the determined commercial power supply frequency. Is A / D converted.

FIG. 2 is a flowchart of this discriminating operation.

When the power is turned on, in step n1,
A / D conversion is performed in a cycle synchronized with 50 Hz for a predetermined period over several cycles of the commercial power source, and in step n2, the average value of the converted values per cycle of the commercial power source (cycle T in FIG. 6) is the same as in the conventional case. Then, the fluctuation range (variation) A of the calculated average value is calculated.

Next, at step n3, similarly, 60H
A / D conversion is performed in a cycle synchronized with z for a predetermined period over several cycles of the commercial power source, and in step n4, the average value of the converted values per cycle T of the commercial power source is calculated, and the calculated average is calculated. The fluctuation range B of the value is calculated.

Then, in step n5, it is judged whether or not the fluctuation width A of 50 Hz is larger than the fluctuation width B of 60 Hz, and if it is larger, the routine proceeds to step n6, where the commercial power supply frequency is discriminated as 60 Hz and thereafter 60 Hz. A / D conversion is performed in a cycle synchronized with. In step n5,
When the fluctuation width A of 50 Hz is not larger than the fluctuation width B of 60 Hz, the process moves to step n7, the commercial power supply frequency is discriminated as 50 Hz, and thereafter A is synchronized with 50 Hz.
/ D conversion is performed.

Thus, the commercial power supply frequency is automatically discriminated and the A / D conversion is performed in the cycle synchronized with the discriminated commercial power supply frequency. Therefore, the influence of the induced noise from the commercial power supply is improved and the conventional example is used. Thus, the user does not need to operate the switch according to the frequency of the commercial power source used.

It is needless to say that the present invention can be applied not only to the case of converting the input at a high speed with respect to the power supply cycle but also to the case of converting the input at a low speed.

[0023]

As described above, according to the present invention, 50 Hz
Since the A / D conversion is performed at a cycle corresponding to 1 Hz and 60 Hz, and the fluctuation of the average value of the converted values is compared to determine whether the commercial power supply frequency is 50 Hz or 60 Hz, as in the conventional example, the user Does not need to operate the switch for setting the A / D conversion cycle in accordance with the power supply frequency, and therefore, a setting error does not occur.

[Brief description of drawings]

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

FIG. 2 is a flowchart for explaining the operation of the embodiment of FIG.

FIG. 3 is a configuration diagram for explaining temperature control of a molding machine.

FIG. 4 is a diagram for explaining the influence of induced noise.

FIG. 5 is a configuration diagram of a conventional example.

FIG. 6 is a diagram for explaining A / D conversion for eliminating the influence of induction noise.

[Explanation of symbols]

 1 electronic temperature controller 2 temperature sensor 3 A / D converter 7 microcomputer (discriminating means)

Claims (1)

[Claims] 1. A for A / D converting an input from a temperature sensor
In an electronic temperature controller equipped with an A / D converter, the input from the temperature sensor is A / at a cycle synchronized with 50 Hz.
The commercial power supply frequency is discriminated by comparing the fluctuation of the average value of the converted values when the D conversion is performed and the fluctuation of the average value of the converted values when the A / D conversion is performed at the cycle in which the input is synchronized with 60 Hz. An electronic temperature controller, comprising: a determining means, wherein the input from the temperature sensor is A / D converted in a cycle synchronized with the commercial power supply frequency determined by the determining means.