JP2770267B2 - Thermobalance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermobalance for measuring a change in weight of a sample according to a change in temperature.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram of a conventional thermobalance. The balance beam 10 is rotatably supported by a fulcrum 12. A sample container 14 is provided at one end of the balance beam 10, and the sample container 14 is disposed inside a heating furnace 15. A sample to be measured is placed in the sample container 14. A shutter 16 having a slit is fixed to the other end of the balance beam 10. In the middle of the balance beam 10 is a movable weight 1
8 is attached so that the imbalance of the balance beam 10 in the initial state can be corrected. The inclination of the balance beam 10 from the horizontal state is detected by the inclination detecting device 20. The tilt detecting device 20 includes a light source 22 and a shutter 16.
And the light receiving device 24. The shutter 16 is a light source 22
Of the light emitted by the light source 22, only the light that has passed through the slit of the shutter 16 reaches the light receiving device 24.

The light receiving device 24 is constituted by arranging a pair of photodiodes. When light passing through the slit of the shutter 16 strikes the light receiving device 24, a signal proportional to the difference between the irradiation areas on the two photodiodes is output. You. That is, a signal corresponding to the inclination of the balance beam 10 is output.
Then, the light source 22 and the shutter 1 are set so that the output of the light receiving device 24 becomes zero when the balance beam 10 is in the horizontal state.
The positional relationship between 6 and the light receiving device 24 is adjusted.

The output of the light receiving device 24, that is, the tilt detection signal 25 is input to a balance control circuit 26. Balance control circuit 2
Reference numeral 6 denotes a PID control circuit, which outputs a control current 27 for returning the balance beam 10 to a horizontal state to the control coil 28 based on the tilt detection signal 25. In the middle of the balance beam 10, a permanent magnet 30 is fixed.
Receives a vertical force by the control current 27 flowing through the control coil 28. Thereby, the balance beam 10 receives a rotational moment, and the horizontal state of the balance beam 10 is maintained.

From the balance control circuit 26, the control current 2
The balance output signal 32 proportional to 7 is output, and is converted by the TG measurement circuit 34 into a measurement signal indicating a change in weight of the sample.

[0006]

In a thermobalance, it is not necessary to measure the weight of the sample itself, but it is sufficient that the change in weight of the sample can be accurately measured. Therefore, if the balance beam is balanced so that the output signal of the balance is almost zero in the initial state of loading the sample, the absolute value of the output signal of the balance will be maintained even if the sample weight increases or the weight of the sample container changes. Precise measurement can be performed without increasing. Therefore, in the conventional apparatus shown in FIG. 3, the movable weight 18 is moved along the balance beam 10 or the weight is added or removed.
The balance beam is balanced so that the control current 27 flowing through the control coil 28 in the initial state where the sample is placed is almost zero. The balance output signal 32 is a signal proportional to the control current 27 (the control current itself may be used).

In order to achieve the initial balance of the balance beam using the movable weight 18, there are the following problems. First, every time the sample is changed, a careful operation of adjusting the position of the movable weight and adding / removing the weight is required, which places a burden on the operator. Second, the mechanical structure of the balance beam is complicated. Third, since the balance room generally has a vacuum-resistant structure, the operation window for operating the movable weight must also have a vacuum-resistant structure.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method for determining a weight change signal of a sample by a simple operation without an operator mechanically operating a weight. An object of the present invention is to provide a thermobalance that can be initially adjusted to fall within a measurable range of the thermobalance.

[0009]

According to the thermobalance of the present invention, a setter for outputting an adjustable initial setting signal is provided in place of the conventional movable weight, and the initial setting signal is subtracted from the balance output signal. Thus, the weight change signal of the sample is set within a predetermined measurable range. That is, the thermal balance of the present invention places a sample on one end of the balance beam, places the sample inside the heating furnace, and applies a rotational moment to the balance beam so that the balance beam maintains a predetermined balance state. A thermometer configured to detect a balance output signal corresponding to the rotational moment and measure a change in weight of the sample; a setting device that outputs an arbitrarily adjustable analog value initial setting signal; and the balance output signal. And a subtractor for subtracting the initial setting signal from the sampler, and measuring a change in weight of the sample based on an output of the subtractor.

It is optimal to set the initial setting signal so that the output signal of the subtractor becomes substantially zero when the sample is in the initial state. However, the present invention is not limited to this. When the sample is in the initial state, a not so large predetermined value may be output as the output signal of the subtractor .

The operation of the present invention will be described. When a sample is placed on a balance beam and the sample is in an initial state (a state before starting measurement), the output of the subtracter is checked while checking the output of the subtractor. Adjust the initialization signal of the setter so that the output is substantially zero (or a predetermined small value). Next, the weight change of the sample accompanying the temperature change is measured while heating the sample in the heating furnace. The output of the subtractor represents a weight change from the initial state of the sample, and the numerical value falls within a predetermined measurable range (for example, ± 250 mg). In the conventional apparatus, a movable weight is used to balance the balance beam in the initial state of the sample, but in the present invention, the final detection signal (subtractor) is used by using the initial setting signal by the setting device. Output signal) within a predetermined measurable range. This eliminates the need for complicated adjustment work of the movable weight. Further, if the movable weight is completely eliminated, a mechanism relating to the movable weight becomes unnecessary.

The mechanism of the movable weight may be left, and a part of the unbalance of the balance beam caused by the weight of the sample and the weight of the sample container may be balanced by the movable weight. Even in this case, the unbalance due to the sample exchange (the unbalance due to the difference in the weight of each sample) is adjusted by the setting device.

The present invention may be applied to a differential thermobalance provided with a balance beam for a sample and a balance beam for a reference material. In that case, an individual setting device is provided for each of the two balance beams, or a common setting device is used.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a configuration diagram of an embodiment of a thermobalance according to the present invention. The balance beam 40 is rotatably supported by a fulcrum 42. A sample container 44 is provided at one end of the balance beam 40, and the sample container 44 is disposed inside a heating furnace 46. A sample to be measured is placed in the sample container 44. A shutter 46 having a slit is fixed to the other end of the balance beam 40. Balance beam 4
The inclination from the horizontal state of 0 is detected by the inclination detecting device 48. The tilt detecting device 48 includes a light source 50, a shutter 46, and a light receiving device 52. The shutter 46 is disposed between the light source 50 and the light receiving device 52. Of the light emitted from the light source 50, only the light that has passed through the slit of the shutter 46 reaches the light receiving device 52.

The light receiving device 52 is constituted by arranging a pair of photodiodes. When light passing through the slit of the shutter 46 hits the light receiving device 52, a signal proportional to the difference between the irradiation areas on the two photodiodes is output. You. That is, a signal corresponding to the inclination of the balance beam 40 is output.
Then, the light source 50 and the shutter 4 are set so that the output of the light receiving device 52 becomes zero when the balance beam 40 is in the horizontal state.
The positional relationship between 6 and the light receiving device 52 is adjusted.

The output of the light receiving device 52, that is, the inclination detection signal 54 is input to a balance control circuit 56. Balance control circuit 5
Reference numeral 6 denotes a PID control circuit, which outputs a control current 58 to the control coil 60 for returning the balance beam 40 to a horizontal state based on the tilt detection signal 54. In the middle of the balance beam 40, a permanent magnet 62 is fixed.
Is subjected to a vertical force by a control current 58 flowing through the control coil 60. Thus, the balance beam 40 receives a rotational moment, and the horizontal state of the balance beam 40 is maintained.

From the balance control circuit 56, the control current 5
A balance output signal 64 proportional to 8 is output. On the other hand, the setting device 66 outputs an initial setting signal 68. The subtracter 70 subtracts the initial setting signal 68 from the balance output signal 64 and outputs the result as a detection signal 72 to the TG measurement circuit 73. The TG measurement circuit 73 calculates a change in weight of the sample based on the detection signal 72.

The balance output signal 64 output from the balance control circuit 56 is a signal proportional to the control current 58 (the control current 5
8 itself). Each time a thermogravimetric measurement is performed on a new sample, the initial control current 58 for balancing the balance beam will be different. In the conventional apparatus, the movable weight is adjusted so that the initial control current 58 is reduced to zero as much as possible. In the present invention, however, the control current 58 may have a large absolute value (the range of the maximum load specification of the balance). I did not mind. Instead, by adjusting the initial setting signal 68 from the setting unit 66, the final detection signal 72 is adjusted to the measurable range (± 25) of the TG measuring circuit 73.
0mg).

The balance adjusting ability (that is, the maximum load specification) of the balance beam 40 of this embodiment is ± 5 g. That is, the control current 58 can be controlled within a range corresponding to a weight of ± 5 g. On the other hand, by adjusting the initial setting signal 68 of the setting device 66, the detection signal 72 is set to be within the measurable range (± 250 mg). Typically, the setting device 66 is set so that the detection signal 72 becomes substantially zero when the sample is placed on the balance beam 40 in the initial state.
Is set. Thus, only the signal corresponding to the change in the weight of the sample is output as the detection signal 72. The detection signal 72 is sent to the TG measurement circuit 73. The TG measurement circuit 73 includes a scaling circuit, a smoothing circuit, a differentiation circuit, a zero shift circuit, and a% (percent) calculation circuit. The output of the TG measurement circuit 73 is supplied to a host computer for data processing, a recorder,
The data is sent to a display device, a temperature control circuit, an atmosphere controller, and the like, and is used for data analysis, recording, temperature control, atmosphere gas control, and the like.

FIG. 2A is a circuit diagram showing a first embodiment of the setting unit 66. A potentiometer 7 is connected to two DC voltage sources 74 and 76 (both having an output of 5 V) connected in series.
8 is connected, and the midpoint between the two DC voltage sources 74 and 76 is grounded. By moving the contact point of the potentiometer 78, an arbitrary voltage value can be output to the set output terminal within a range of ± 5V. As a specific setting method, the detection signal 7 is set in an initial state where the sample is placed on the balance beam.
While displaying the measured value corresponding to 2 on the display device, the potentiometer 78 is adjusted so that the measured value becomes zero, and an optimal initial setting signal is obtained.

FIG. 2B is a block diagram showing a second embodiment of the setting unit 66. When a digital set value is set by the host computer 80, the digital set value is converted into an analog signal by the digital / analog converter 82 and output to the set output terminal. By properly adjusting the setting range of the host computer 80 and the conversion voltage of the digital-to-analog converter 82, the output range of the setting output terminal can be set to a range of ± 5V. The host computer 80 used in the setting device is a host computer used for data processing of measured values, sample temperature control, and the like. The setting method using the setting device also adjusts the digital setting value of the host computer 80 while watching the display of the measured value, as in the embodiment of FIG. Alternatively, the host computer 8
When the storage function of 0 is used, the initial setting value for balancing the balance beam may be automatically determined with reference to sample conditions and the like measured in the past.

FIG. 2C is a block diagram showing a third embodiment of the setting unit 66. When a digital set value is set by a digital switch 84 (a multi-digit decimal switch), the digital set value is converted by a control circuit 86 to become a digital signal suitable as an input signal to a digital / analog converter 88, which is further converted into a digital / analog signal. Bowl 88
Is converted to an analog signal and output to the setting output terminal. By appropriately adjusting the setting range of the digital switch 84, the conversion specification in the control circuit 86, and the conversion voltage in the digital / analog converter 88, the output range of the setting output terminal can be set to a range of ± 5V. As in the embodiment of FIG. 2A, the setting method according to this embodiment is also initialized by increasing or decreasing the digital switch 84 while observing the display of the measured values.

[0023]

According to the thermal balance of the present invention, the initial setting signal is subtracted from the balance output signal. Therefore, even if the sample weight is different, the detection signal can always be measured by adjusting the initial setting signal. Can be in the range. This eliminates the need for complicated adjustment of the movable weight and facilitates the initial setting of the thermobalance. It is also possible to eliminate the movable weight, in which case the mechanism of the balance beam is simplified.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of a thermobalance according to the present invention.

FIG. 2 is a configuration diagram showing various forms of a setting device.

FIG. 3 is a configuration diagram of a conventional thermobalance. .

[Explanation of symbols]

 40 Balance Beam 44 Sample Container 46 Heating Furnace 48 Tilt Detector 54 Tilt Detection Signal 56 Balance Control Circuit 58 Control Current 60 Control Coil 62 Permanent Magnet 64 Balance Output Signal 66 Setting Device 68 Initial Setting Signal 70 Subtractor 72 Detection Signal 73 TG Measurement circuit

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-9-26402 (JP, A) JP-A-60-72553 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01N 5/04

Claims (5)

(57) [Claims] 1. A sample is placed on one end of a balance beam, the sample is placed inside a heating furnace, and a rotational moment is applied to the balance beam so that the balance beam maintains a predetermined balance state. In a thermobalance configured to detect a balance output signal corresponding to and measure a change in weight of a sample, a setting device that outputs an arbitrarily adjustable analog value initial setting signal, and the initial setting from the balance output signal. A thermobalance comprising: a subtractor for subtracting a signal; and measuring a weight change of the sample based on an output of the subtractor. 2. The subtractor when a sample is in an initial state .
The thermobalance according to claim 1, wherein the initial setting signal is set so that the output signal of the thermobalance is substantially zero. 3. A tilt detecting device for detecting a tilt of the balance beam, and a control coil for giving a rotational moment to the balance beam, wherein a current flowing through the control coil is controlled according to an output signal of the tilt detecting device. 2. The thermobalance according to claim 1, wherein the thermobalance is controlled and a signal proportional to the current value is used as the balance output signal. 4. The thermobalance according to claim 1, wherein the setting device includes a DC voltage source and a potentiometer. 5. The thermobalance according to claim 1, wherein the setting device comprises a means for setting a digital setting device, and a digital / analog converter for converting the digital setting value into an analog value.