JPS5820930Y2 - Constant temperature chamber temperature control device - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a device that adjusts the temperature of a plurality of constant temperature chambers of an analysis device such as a gas chromatograph to a predetermined temperature.

For example, a column constant temperature bath is used for a gas chromatograph.

There are multiple constant temperature chambers, such as a sample chamber constant temperature chamber and a detector constant temperature chamber, each of which requires independent temperature control.

As shown in Figure 1, the conventional method for adjusting the temperature of this thermostatic chamber is to measure the temperature of the thermostatic chamber using a current flowing through a platinum resistor, convert this measured value into voltage, and then set the temperature using a comparator. In this method, the temperature is adjusted by comparing the values and controlling the heater on and off through a heater current controller based on the comparison result.

In addition, the voltage-converted temperature value is analog-digital (A
-D) It is also converted into digital data using a converter and displayed directly as a number.

However, in this conventional method, a control unit or display device is required for the number of thermostats, and if a single display device is to be used, a changeover switch is required as shown in Figure 1, and a temperature control device is required. The disadvantage was that it was complicated.

Additionally, in devices that detect extremely small signals, such as gas chromatographs, spike noise that occurs when turning on and off the AC power supply for the heater is a problem, so measures must be taken to prevent this noise from occurring. The current supply to the heater is turned on and off at the phase where the current becomes zero (hereinafter referred to as Xerox switching).

Therefore, even in the conventional case, a mechanism for performing this zero-cross switching is required in the above-mentioned control section, and providing this zero-cross switching for each constant temperature type makes the control section even more complicated.

The present invention attempts to provide a constant temperature bath temperature control device that solves the above-mentioned problems, and the main part thereof is a constant temperature bath temperature control device that consists of the following combinations of (1) to (6). .

(1) A heater heated by alternating current supplied via a switching element arranged in each of a plurality of constant temperature ovens, and a detection element that detects the internal temperature caused by this heating.

(2) A pulse generator that generates a zero phase pulse signal indicating the zero phase of the alternating current.

(3) A clock pulse generator that generates a clock pulse signal at a shorter period than the zero-phase pulse signal.

(4) A multiplexer that selects the output of any one of the plurality of detection elements according to the clock pulse signal.

(5) An A-to-digital converter that converts the output of the multiplexer from analog to digital and outputs a temperature measurement digital signal.

(6) A control device comprising each means of (a) to (d).

(a) Means for holding digital signals corresponding to the set temperatures of each of the thermostats.

(b) Means for comparing the temperature measurement signal of the detection element of the selected thermostatic oven with the set temperature digital signal of the corresponding thermostatic oven.

(C) Means for sequentially storing the results of this comparison.

(d) Means for transmitting a signal to the switching element based on the comparison result stored by generation of the zero phase pulse signal.

That is, the present invention shares the central part of the temperature control device for each thermostat (for example, a microcomputer seems to be suitable for use in this configuration.

), the aim is to realize a control device that is extremely simple and capable of zero-cross switching.

The following description will be made with reference to FIG. 2, which is a schematic diagram of one embodiment of the present invention.

In Fig. 2, 1 is a gas chromatograph, 11 and 12 are thermostats, 112 and 114 are heaters, 111° and 113 are temperature detection elements, 2 is a multiplexer, 3 is a resistance voltage converter, 4 is an A-D converter, and 5 is a control device (detailed later), 6
1 is a keyboard, 7 is a display device, 8 is a commercial power source, 9 is a zero-phase pulse generator, and 13° and 14 are bidirectional thyristors.

The control device 5 also includes a microprocessor 51, a fixed memory 52, a temporary memory 53, an input terminal 54, an output terminal 55, and the like.

First, the multiplexer 2 is driven by a pulse signal from a (clock) pulse generator (not shown) that generates a (clock) pulse signal at a shorter period than that period in relation to the zero-phase pulse. 11 detection element 111 is selected, and the resistance voltage converter 3 selects this detection element 11.
The temperature measurement digital signal which is converted into a voltage through the A/D converter 4 is introduced into the control device 5 and is temporarily stored in the memory 53.

On the other hand, the set temperature of each thermostatic oven is converted into a corresponding digital signal via the keyboard 6, and each is temporarily held in the memory 53.

The microprocessor 51 then compares the previously measured temperature digital signal with the corresponding set temperature digital signal, and causes the comparison result to be temporarily held in the memory 53.

Then, as the zero-phase pulse from the pulse generator 9 is introduced into the control device 5, if the comparison result stored in the temporary memory 53 instructs the heating of the heater 112, the bidirectional thyristor 13 is activated. The opening signal is this control device 5
A half cycle of alternating current flows through the heater 112.

On the other hand, the comparison result based on the temperature measurement signal from the detection element 113 is also temporarily stored in the memory 53, so if the comparison result at this time is an instruction to heat the heater 113, the thyristor 14 is also An open signal is sent from this controller 5, and a half cycle of alternating current flows through the heater 114.

Of course, if the comparison result does not indicate heating of the heater, no alternating current will flow through the heater.

Further, the operation of the microprocessor 51 or the order of these operations is performed according to a program written in a fixed memory 52, and signals between the control device 5 and each external device are transmitted through an input terminal 54 and an output terminal 55. The delivery will take place.

The display device 7 selects and displays one of the temperature measurement signals stored in the temporary memory 53.

If a printer is used as the display device 7, the actual temperature value can be printed.

FIG. 3 is an explanatory diagram of the above-mentioned zero phase pulse, in which waveform a shows the waveform of the AC power supplied to the heater, and this waveform a is energized to the input side of the pulse generator 9.

The waveform is a waveform of a zero phase pulse indicating that the voltage of the power supply is zero, and is output from the pulse generator 9.

In this example, the temperature of all thermostatic chambers was measured during one interval of the zero-phase pulse, but if the thermal response between the heater heat generation and the detection element is slow, the temperature of the zero-phase pulse is measured. The temperature may be measured for each type of constant temperature at several intervals; in this case, a low-speed A-D converter 4 will suffice.

As described in detail above, the present invention simplifies the temperature control section of each thermostatic chamber, which was previously provided separately, by using one control section in a time-sharing manner. By performing the process from detecting the temperature to comparing it with the set temperature within the cycle interval of the zero-phase pulse signal, AC current control (zero cross switching) using the zero-phase pulse signal can be performed accurately without any time delay, and the heater can be turned on.・It is possible to completely prevent the generation of noise caused by turning off.

[Brief explanation of drawings]

Figure 1 is a schematic explanatory diagram of a conventional thermostat temperature control device, Figure 2
The figure is a schematic explanatory diagram of a constant temperature chamber temperature control device according to the present invention, and FIG. 3 is an explanatory diagram of a zero phase pulse. 1... Gas chromatograph, 2... Multiplexer, 3... Resistance voltage converter, 4...
...A-D converter, 5...Control device, 6.
...Keyboard, 7...Display device, 8.
... Commercial power supply, 9 ... Pulse generator, 1
1.12... Constant temperature bath, 112,114...
... Heater, 111, 113 ... Temperature detection element, 51 ... Microprocessor, 52 ...
... Fixed memo, 53 ... Temporary memory, 54.
...Input terminal, 55...Output terminal.

Claims (1)

[Claims for Utility Model Registration] A constant temperature chamber temperature control device that is claimed by the following (1) to (6). (1) A heater heated by alternating current supplied via a switching element arranged in each of a plurality of constant temperature ovens, and a detection element that detects the internal temperature caused by this heating. (2) A pulse generator that generates a zero phase pulse signal indicating the zero phase of the alternating current. (3) A clock pulse generator that generates a clock pulse signal at a shorter period than the zero-phase pulse signal. (4) A multiplexer that selects the output of any one of the plurality of detection elements according to the clock pulse signal. (5) An A converter that converts the output of the multiplexer from analog to digital and outputs a temperature measurement digital signal. (6) A control device comprising each means of (a) to (d). (a) Means for holding a digital signal corresponding to the set temperature of each thermostatic oven. (b) Means for comparing the temperature measurement signal from the detection element of the thermostatic oven of the selected detection element with the digital signal of the set temperature of the corresponding thermostatic oven. (C) Means for sequentially storing the results of this comparison. (d) Means for transmitting a signal to the switching element based on the comparison result stored by generation of the zero phase pulse signal.