JP2811875B2 - Analytical heating furnace temperature controller - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a technique for controlling the temperature of a furnace for heating a sample such as a thermal analyzer.

(Prior Art) For example, in a thermal analyzer, a sample cell and a standard substance cell are usually housed in a heating furnace in pairs, and the same thermal energy change is applied to both cells. The difference is detected and the composition of the sample is analyzed. Such a change in the thermal energy is performed by changing the current supplied to the heating furnace at a constant speed by a temperature control device.

By the way, the heating furnace used in the thermal analyzer is made extremely precisely and is extremely fragile to overheating. Measures have been taken to protect the heating furnace.

(Problems to be Solved by the Invention) However, if the temperature sensor is damaged, the current rapidly increases to the current value that is full of the limited current, the sample temperature rises rapidly, and an explosion occurs depending on the substance. There was fear.

The present invention has been made in view of such a problem, and an object of the present invention is to provide an analytical method capable of preventing a rapid rise in temperature of a heating furnace regardless of a failure of a heating temperature detecting unit. An object of the present invention is to provide a thermal analyzer equipped with a novel temperature control device for a heating furnace.

(Means for Solving the Problems) In order to solve such a problem, in the present invention,
A means for detecting a current supplied to a heater for heating the sample container; a current change rate detecting means for detecting a change rate of the current; a maximum value storage means for setting an allowable change rate of the current; Comparing means for comparing the signals from the speed detecting means and the maximum value storing means and outputting a signal when the current change speed exceeds a set value; and means for cutting off the current supply to the heater by a signal from the comparing means. I prepared for it.

(Operation) The change rate of the current supplied to the heating furnace is compared with a reference value,
When the rate of increase of the current exceeds the reference value, the supply of the current to the heating furnace is stopped.

(Embodiment) Therefore, the details of the present invention will be described below based on an illustrated embodiment.

FIG. 1 shows one embodiment of the present invention. In the drawing, reference numeral 1 denotes a heating furnace for heating a sample cell 2 and a standard substance cell 3, and a heater 4 from a current regulator 9 described later. It is configured to receive a current supply. Thermocouples 5 and 6 are differentially connected to the sample cell 2 and the standard substance cell 3, respectively.
It is configured to detect the temperature difference of. One output of the thermocouples 5 and 6 is supplied to a PID control circuit 1 via an amplifier 8.
Output to 2.

On the other hand, the heater 4 has a current regulator 9, a current detector 10,
And the circuit breaker 11 are connected in series, and electric power is supplied from a commercial electric power source. Reference numeral 12 denotes a PID control circuit for setting the proportional, integral, and differential constants. The PID control circuit receives a temperature signal from the amplifier 8 and a signal from the heating rate setting device 13, and receives a signal from the heating rate setting device.
The current to heater 4 is adjusted via current adjuster 9 so that the temperature rises at the speed set by 13.

Numeral 14 denotes a differentiating circuit for differentiating a signal from the current detector 10 and detecting an increasing speed ΔI / ΔT of the current supplied to the heater 4. Reference numeral 15 denotes a maximum current increase speed storage circuit which stores the maximum current increase speed allowed for the temperature increase speed set in the temperature increase speed setting device 13 and outputs it to a comparison circuit 16 described later. A comparison circuit 16 compares the signals from the differentiating circuit 14 and the maximum current increasing speed storage circuit 15 and outputs a signal for turning off the circuit breaker 11 when they match.

In this embodiment, when the sample is stored in the sample cell 2 and the standard substance is stored in the standard substance cell 3 and the apparatus is operated,
The PID control circuit 12 supplies a current for realizing the heating rate set in the heating rate setting device 13 to the heater 4 via the current regulator 9 to increase the temperature. Thereby, the sample cell 2
Causes an endothermic or exothermic reaction based on its composition and the like. The endothermic and exothermic reactions are detected by the thermocouples 5 and 6 as a temperature difference between the cells 5 and 6. In this manner, the characteristics of the sample can be known by causing the heater 4 to generate heat to the predetermined temperature at the heating rate set in the heating rate setting device 13.

In parallel with such a temperature raising operation, the differentiating circuit 14 receives the current value signal from the current detector 10 and receives the current increasing rate ΔI / Δ
T is detected. When operating normally, the increasing speed ΔI / ΔT does not exceed the maximum current increasing speed stored in the maximum current increasing speed storage circuit 15.

On the other hand, when the temperature of the heating furnace 1 cannot be detected due to the disconnection of the thermocouples 5 and 6, the PID control circuit 12 determines the difference between the signal from the heating rate setting device 13 and the temperature signal from the thermocouple 6, that is, the error. The current is rapidly increased by the current regulator 9 in order to make the signal into a signal (a portion indicated by a chain line in FIG. 2). That is, since there is no input of the temperature signal, the PID control circuit 12 considers that the temperature of the heating furnace 1 is extremely low, and performs an operation of supplying an extremely large current to reach the set temperature.

For this reason, the change rate ΔI / ΔT of the current detected by the differentiating circuit 14 becomes extremely large and exceeds the value of the maximum current increasing speed storage circuit 15, so that the comparing circuit 16
Outputs a signal, turns off the circuit breaker 11, and cuts off the current supply to the heater 4.

As a result, the temperature rise of the heater 4 is stopped, and a rapid temperature rise of the sample is prevented.

FIG. 3 shows a second embodiment of the present invention. In the figure, reference numeral 20 denotes a maximum current operation circuit which operates the heating furnace 1 at the heating rate set by the heating rate setting unit 13. The current value at that time is detected by the current detector 10, and the value I _m (T _s ) obtained by multiplying the current I (T _s ) at each time point (T _s ) by a constant ratio K, for example, 1.01 to 1.1, is maximized. It is configured to output to the current value storage circuit 22. A comparison circuit 21 compares the comparison data I _m (T _s ) of the maximum current value storage circuit 22 with the current value I (T _s ) from the current detector 10 and determines that the current value I (T _s ) is the maximum. When the value exceeds the value _Im (T _s ) of the current value storage circuit 22, a signal for turning off the circuit breaker 11 is output.

In this embodiment, prior to the analysis, the heating furnace 1 is operated at the heating rate set in the heating rate setting unit 13 without storing the sample in the heating furnace 1. Arithmetic circuit
22 is a current value I from the current detector 10 at each time point (T _s ).
A value _Im (T _s ) obtained by multiplying (T _s ) by a constant ratio K is stored in the maximum current value storage circuit 22.

When the comparison data for the current up to the maximum temperature is stored in this way, the heating furnace 1 is returned to room temperature, the sample is stored, and the heating furnace 1 is operated again. Comparison circuit 21, in accordance with the operation timings of the heating rate setting circuit 13 reads the maximum current value comparing data I _m from the storage circuit 22 (T _s), from the data I _m (T _s) and the current detector 10 Compare the value I (T _s ). When the temperature of the heating furnace 1 is rising at the heating rate set in the heating rate setting unit 13, the current value of the heating furnace 1 is compared with the comparison data I _m (T _s ) of the maximum current value storage circuit 22. Is not exceeded.

On the other hand, if the temperature signals from thermocouples 5 and 6 are interrupted, PI
The D control circuit 12 causes the current regulator 9 to rapidly increase the current so as to make the difference between the signal from the heating rate setting device 13 and the temperature signal from the thermocouples 5 and 6, that is, the error signal zero. Become.

Therefore, the current value I detected by the current detector 10 is
Since (T _s ) exceeds the value of the comparison data _Im (T _s ) stored in the maximum current value storage circuit 22, the comparison circuit 21
Outputs a signal to turn off the current breaker 11 and turn on the heater 4.
Will cut off the current to.

In the above-described embodiment, an example has been described in which the present invention is applied to a thermal analyzer. However, it is apparent that the same effect can be obtained by applying the present invention to another heating furnace such as a sample heating furnace of a gas chromatograph. It is.

(Effect of the Invention) As described above, in the present invention, a means for detecting a current supplied to a heater for heating a sample container, a current change speed detecting means for detecting a change speed of the current, and an allowable current A maximum value storage means for setting a change rate of the current, a comparison means for comparing signals from the current change rate detection means and the maximum value storage means and outputting a signal when the current change rate exceeds a set value; A means to cut off the current supply to the heater by the signal from the heater, so that even if the temperature signal from the heating furnace is interrupted, the current supply to the heating furnace is stopped immediately to prevent a sharp rise in temperature. can do.

[Brief description of the drawings]

FIG. 1 is a block diagram of an apparatus showing one embodiment of the present invention, FIG. 2 is a diagram showing the operation of the above apparatus, and FIG. 3 is a block diagram showing another embodiment of the present invention. 1 ... heating furnace, 2 ... sample cell 3 ... standard material cell, 4 ... heater 5, 6 ... thermocouple, 7, 8 ... preamplifier

Claims (2)

(57) [Claims] 1. A means for detecting a current supplied to a heater for heating a sample container, a current change rate detecting means for detecting a change rate of the current, and a maximum value storage for setting an allowable current change rate. Means for comparing a signal from the current change rate detection means and the maximum value storage means to output a signal when the current change rate exceeds a set value; and a current to the heater based on a signal from the comparison means. An analysis furnace temperature control device comprising means for cutting off the supply. 2. A current detecting means for detecting a current supplied to a heater for heating a sample container, a current changing rate detecting means for detecting a changing rate of the current, and a temperature increasing means for setting a temperature increasing rate of the heater. Speed setting means, calculating means for calculating the maximum value of the current allowed from the heating rate, maximum current storing means for storing the calculation result, and comparing the values of the current detecting means and the maximum current storing means. An analysis furnace temperature control apparatus comprising: a comparison unit that outputs a signal when a current to a heater is exceeded; and a unit that cuts off current supply to the heater in accordance with a signal from the comparison unit.