JPH0580005A - Differential thermal balance - Google Patents

Abstract

PURPOSE:To eliminate an influence due to difference in inclination of beam between a sample-side balance and a reference substance side balance. CONSTITUTION:A sensor 10a at a position-detection part of a reference substance side balance is fixed to a beam 4 of a sample side balance. When the weight of a measurement sample changes due to heating of sample pans of both balances, a current corresponding to the weight change flows to a feedback coil 12. However, when the beam 4 is balanced at a slightly inclined position, the sensor 10a at the reference substance side is displaced accordingly and a relative position with a shutter 8a also changes, thus enabling a current of a feedback coil 12a at the reference substance side to be changed and a beam 4a of the reference substance side balance also to be inclined by an amount which is equal to that of the beam 4 of the sample side balance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermobalance used in a thermal analysis apparatus, and more particularly to a feedback for balancing a beam, which is provided with a sample plate at one end of the beam and a position detecting section composed of a sensor and a shutter at the other end. The present invention relates to a differential thermal balance in which a balance equipped with a coil is provided on each of a sample side and a reference material side.

[0002]

2. Description of the Related Art In order to eliminate the influence of signal drift caused by the balance itself from the signal of the weight change obtained from a thermobalance, a sample side balance on which a measurement sample is placed, and a standard with the same structure as that for not placing a sample A differential thermobalance is used in which the detection signal of the reference material side balance is subtracted from the detection signal of the sample side balance under the same conditions as possible for the material side balance.

[0003]

When a differential thermal balance is used for measurement, when the weight of the sample to be measured changes, the shutter of the position detecting section is displaced, and the sensor detects it, and the shutter is released. Current is applied to the feedback coil so as to eliminate the tilt of the beam to return to the position. The current is detected as a weight signal. However, although the tilted beam tries to be returned to the original state by energizing the feedback coil, it does not return to the original state correctly, and stops in a slightly tilted state. On the other hand, since the beam does not tilt in the balance on which the sample is not placed, a difference in tilt occurs between the beam of the sample side balance and the beam of the reference material side balance. As the fulcrum of the balance, for example, a torsion band or an elastic fulcrum is used, but the force applied to the fulcrum changes depending on the tilt angle of the beam at these fulcrums. When occurs, the influence of the force at the fulcrum appears as an error in the detection signal. An object of the present invention is to provide a differential type thermobalance capable of eliminating the influence of the difference in beam tilt between the sample side balance and the reference material side balance.

[0004]

In the present invention, the tilts of the beams of both balances are made equal. Therefore, in the present invention, the sensor of the position detection unit of the reference material side balance is fixed to the beam of the sample side balance, or the current flowing in the feedback coil of the sample side balance is approached to the feedback coil of the reference material side balance. A second feedback coil is provided that flows in the opposite direction to the side balance.

[0005]

In the invention in which the sensor of the position detecting section of the reference material side balance is fixed to the beam of the sample side balance, when the beam of the sample side balance tilts due to the weight change of the sample, the reference material side balance corresponds to the tilt of the beam. The sensor of the position detecting section of (1) is displaced, and the beam of the reference material side balance is tilted by the same angle as the beam of the sample side balance accordingly. In the invention in which a second feedback coil is provided which causes a current flowing in the feedback coil of the sample side balance to approach the feedback coil of the reference material side balance in a direction opposite to that of the sample side balance, the beam of the sample side balance is changed by the weight change of the sample. Is tilted, the force applied to the reference material side balance through the second feedback coil of the reference material side balance is changed, so that the beam of the reference material side balance is tilted accordingly. In this way, if the balance of the beam on the sample side balance is slightly tilted due to the weight change of the sample, the balance is also maintained on the reference material side balance with the beam tilted by the same tilt, and the beam between the two balances is balanced. The influence of the difference in the slope of is eliminated.

[0006]

FIG. 1 shows an embodiment corresponding to the invention of claim 1. FIG. 2 is a partially enlarged view of the position detector in the embodiment of FIG. In the sample side balance S, a sample pan 6 on which a sample is placed is fixed to one end of a beam 4 which rotates around a fulcrum 2 by a torsion band, and a shutter 8 is attached to the other end of the beam 4.
Is installed. The shutter 8 is combined with a sensor 10 fixed to the main body of the balance device to form a position detector. The sensor 10 is of an optical type including, for example, an LED and a phototransistor. A feedback coil 12 is attached to an intermediate position of the beam 4, and the feedback coil 12 is inserted into a permanent magnet 14 to be assembled. The shutter 8 of the position detector is a sensor 10
Feedback coil 12 so that it comes to a fixed position in
A feedback coil current generation circuit (not shown) for supplying a current to generate a force is provided, and the current is detected as a weight signal.

The reference material side balance B has the same structure. However, in the reference substance side balance R, the sensor 10a of the position detecting portion is fixed to the beam 4 of the sample side balance via the fixing metal fitting 16 as shown in FIG. In order to distinguish each part of the reference material side balance R from each part of the sample side balance S,
The symbol a for each part of the reference substance side balance R is attached.

At the time of measurement, the measurement sample is placed on the sample dish 6 of the sample side balance, and nothing is placed on the sample dish 6a of the reference material side balance. To heat. When the weight of the sample to be measured changes due to the heating of the sample pan of the double balance, a current according to the change in weight flows to the feedback coil 12, but when the beam 4 is balanced at a slightly tilted position, the reference material is changed accordingly. Since the sensor 10a on the side is displaced and the relative position to the shutter 8a is changed, the current of the feedback coil 12a on the reference material side is changed, and the beam 4a of the reference material side balance is tilted by the same amount as the beam 4 of the sample side balance. ..

FIG. 3 shows an embodiment corresponding to claim 2. FIG. 3 (A) shows the balance on both the sample side and the reference material side, and FIG. 3 (B) shows the coupling relationship of the feedback coils. The structure of both balances is the same as that shown in FIG. 1, but the sensor 10a of the reference material side balance R is not fixed to the beam 4 of the sample side balance, but is the same as the sample side sensor 10. It is fixed to the device body. The feedback coil 12 of the sample side balance and the feedback coil 12a of the reference material side balance are wound in the same direction on the respective cores, but in the core of the reference material side balance is wound in the opposite direction in addition to the feedback coil 12a. The second feedback coil 20 is wound. The sample side feedback coil 12 is connected to the feedback coil current generation circuit 22 and also connected to the second feedback coil 20 wound around the core on the reference material side. 24 is the feedback coil 12 of the reference material side balance
It is a feedback coil current generation circuit of a.

In the embodiment of FIG. 3, the structure of both balances is the same as that of FIG. 1, but the sensors of the position detecting section are independent of each other, and instead the current flowing in the feedback coil 12 of the sample side balance is on the reference material side The feedback coil 12a also flows. Feedback coil 12 on the sample side when the measurement sample changes in weight due to temperature
Current Is flows to the reference material side feedback coil 1
It is assumed that the current Ir flows through 2a. Is = Iδw-Iθ. Iδw is a current corresponding to the weight change of the sample, and Iθ is a current flowing due to the influence of the inclination θ of the fulcrum of the beam 4. On the other hand, since the current Is flows in the opposite direction in the second feedback coil 20 on the reference material side, in order to cancel the inclination of the beam 4a generated thereby, Is and the beam 4a at the balance position in the feedback coil 12a are canceled. The difference from the current Iθ due to the influence of the inclination θ,
That is, Ir = Is−Iθ = Iδw−2Iθ flows. In order to obtain the weight change from the detection signal of the two balances, the signal Is on the sample side is amplified twice and then the signal Ir on the reference material side is subtracted to cancel the influence of the tilt of the beam and the signal Iδw of the weight change. Can be asked.

FIG. 4 shows another example of the elastic fulcrum. A bent portion 26 is provided at the center, a support rod is inserted into and supported by a lower hole, and a beam is inserted through an upper hole 30 to elastically support the beam.

[0012]

According to the present invention, the sensor of the position detecting portion of the reference material side balance is fixed to the beam of the sample side balance, or the current flowing in the feedback coil of the sample side balance approaches the feedback coil of the reference material side balance. Is provided with a second feedback coil that flows in the opposite direction to the sample side balance,
Since the beams of both the balance on the sample side and the beam on the reference substance side always have the same inclination, by taking the difference between the detection signals of the two balances, the measurement without the influence of the inclination of the beam can be performed.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing an embodiment corresponding to claim 1. FIG.

FIG. 2 is an enlarged perspective view showing a position detector of the embodiment of FIG.

FIG. 3 is a diagram showing an embodiment corresponding to claim 2;
(A) is a perspective view of the balance mechanism, (B) is a circuit diagram showing the connection relationship of the feedback coil.

FIG. 4 is a perspective view showing an elastic fulcrum as an example of a fulcrum used in the embodiment.

[Explanation of symbols]

 S sample side balance R reference material side balance 2,2a fulcrum 4,4a beam 6,6a sample dish 8,8a shutter 10,10a sensor 12,12a feedback coil 14,14a permanent magnet 20 second feedback coil

Claims (2)

[Claims] 1. A balance having a sample dish at one end of the beam and a position detection unit comprising a sensor and a shutter at the other end, and a balance equipped with a feedback coil for the beam, one set on each of the sample side and the reference substance side. A differential thermobalance, in which the sensors of the position detection part of the reference material side balance are fixed to the beam of the sample side balance. 2. A balance having a sample dish at one end of the beam and a position detection unit composed of a sensor and a shutter at the other end, and a feedback coil for balancing the beam, one set each on the sample side and the reference substance side. The differential type heat generator is provided with a second feedback coil that is provided for each of them and that is close to the feedback coil of the reference material side balance and further causes a current flowing in the feedback coil of the sample side balance to flow in the opposite direction to the sample side balance. Balance.