JPS60100039A - Zero adjustor for automatically recording heat analysis - Google Patents

Abstract

PURPOSE:To enable an automatically recording analysis with a high accuracy by compensating for the temperature difference between the standard sample and a sample immediately after the change in the furnace temperature starts with a servo mechanism only while the temperature changes sharply to prevent missing of observation record due to changes in the zero point. CONSTITUTION:A sample 2 and the standard sample 3 are arranged side by side in a furnace 1 whose temperature rises or lowers linearly and contacts 4 and 5 of a differential thermocouple are bonded on the samples 2 and 3. The temperature difference between the samples 2 and 3 is computed with a differential amplifier 8 through these contacts 4 and 5 and the temperature of the sample 2 via an amplifier 13 is measured with an automatic recorder 10 with the base line based on the temperature difference as zero to perform an analysis on the sample 2. In this case, with a switch 20 closed as controlled with a timer 21, a potentiometer 16 is controlled through a servo motor 19 to allow a servo compensation for the temperature difference while the furnace temperature changes sharply after the start of rise or the like thereof and the amplifier 8 is fixed to the compensated value after the temperature difference is stabilized. This prevents missing of record at the observation part due to variations in the base line thereby enabling a automatically recording analysis with a high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION In differential thermal analysis, scanning type differential calorimeter, etc., two junctions of a differential thermocouple are connected to a sample and this sample (a standard sample with close thermal conductivity and heat capacity, that is, a reference temperature point). Automatic recording of the output of the differential thermocouple is performed by placing each of these in a furnace and continuously raising or lowering the temperature of the thermocouple.

In such automatic recording thermal analysis, it is virtually impossible to accurately match the heat capacity, etc. of a sample and a standard sample. Therefore, when the temperature of the furnace is raised or lowered at a constant rate, unless there is a change in the thermal properties of the sample, the differential thermocouple will send out a constant output corresponding to the rate of temperature change C: Differential temperature can be recorded using this output level as a baseline. However, the temperature rises 72
Immediately after the temperature starts to decrease, large fluctuations occur in the direction of the differential thermocouple, and especially in highly sensitive measurement equipment, this fluctuation alone can cause the baseline of the automatic recording needle to overscale. occurs, making measurement impossible. For this reason, conventionally it has been necessary to use a standard sample with thermal properties very similar to those of the sample, which requires a great deal of effort in weighing and the like. The present invention eliminates these drawbacks and facilitates particularly high-precision analysis.
This is what I did to get it.

FIG. 1 is a diagram showing the circuit configuration of an embodiment of the present invention, in which two samples 2 and a standard sample 3'ft are juxtaposed in a vertically arranged circle III-shaped electric Fl, and the contact numbers of differential thermocouples are placed on them. and 5 are attached respectively. That is, the standard sample 3 is the reference temperature point, and the input resistance 6. ? -i,'9 The ends of the differential thermocouple of the lever are connected to the input terminal of a differential operational amplifier 8, and the amplifier is provided with a feedback resistor 9, and its output is sent to one of the two manual automatic recorders 10ζ. Add as input. Also, connect both ends of the thermocouple with contact numbers attached to sample 2.
The input terminal of the operational amplifier 13 (
Connect the two, and provide the amplifier direct feedback resistor 141iH,
Its output is all the recorder 10 (- plus as input to the other).

Therefore, when the temperature of the furnace 1 is raised from, for example, room temperature at a constant rate, the temperature of the sample 2 is amplified by the amplifier 13, and the temperature of the sample 2 is amplified by the recorder 10 (= the temperature between the sample g and the standard sample 3 is simultaneously recorded). The difference is amplified by an amplifier 8 and recorded on the same recording needle.The curve PFi in FIG. 2 shows the recorded temperature of the sample 2, where the horizontal axis - is time and the vertical axis T is temperature.

In addition, an input resistor 1 is connected to one input terminal of the differential operational amplifier 8.
Connect the slider 1 of variable potentiometer 16 through 5, that is, the output end of this potentiometer 1.
Reference numeral 6 has a neutral point grounded, and the output of the amplifier 8 is amplified by a servo amplifier 1B to drive a servo motor 19 (= in addition to the amplifier 18 and the motor 19) which drives the slider 17.
A switch ``go'' is provided between ``C2'' and ``C2'' so that this switch is opened by a timer +11, for example.

At time 1 in FIG. (=Assuming that the temperature of furnace 1 has started to rise, the temperature of sample 2 will change as shown in the curve P above, and at the same time, the sinitimer Blf will start. In this case, sample 2 and standard sample 3 If the heat capacity and surface radiant heat absorption characteristics are perfectly equal to C2, the above temperature rise will not cause a temperature difference between sample 2 and standard sample 3, so the output of differential amplifier B will be kept at zero. However, since it is usually difficult to exactly equalize the heat capacity, etc., a temperature difference occurs between the sample record and the standard sample 3. When performing measurements, a large output is sent out from the amplifier 8, but this output reaches a certain value and stabilizes after a certain period of time (:) when the rate of rise or fall of the furnace temperature is constant.

Therefore, at the start of temperature rise, etc., move the recording pen to the recording range @W.
If it is placed in the center of , it deviates from Hw shown by the broken line Q in FIG. 2, for example.

However, the device shown in Figure @1 further increases the output of amplifier 8 by I1. i
The motor is amplified by the servo motor 19 (in addition, the slider 17 of the potentiometer 16 is
I'm sorry. Therefore, when amplifier 8 generates an output,
A voltage corresponding to the output signal is sent out from the slider 17, and an input is fed back to the amplifier 8 through the input resistor 1fi (0, which cancels out the output of the amplifier 8). Therefore, the output of amplifier B is r
A recording line R approximately parallel to the time axis is drawn on the recorder 10 by keeping 4il of zero in f.

Therefore, the time limit of the timer is set to point 1 in Figure C2, or the time until point t1 when the curve Q becomes stable, for example, 1 minute, and the temperature rise or fall of the furnace L is started.
sIf you start that timer at the same time, the above time point 1
At x, timer gl is activated and switch 20 is opened. For this reason, the servo motor 19 stops, and after that, from the slider 17 of the potentiometer 16,
The voltage at
Since the humidity difference between the sample 3 and the standard sample 3 is partially maintained and does not change, a horizontal recording line 8 is drawn by the output of the amplifier 8. However, the temperature of furnace 1 was TttF
If it is assumed that there is a change in the thermal properties of the sample 8 when it reaches iTmaC, then at that point, the curves X and Y as described above will be created in the recording line 8 at I and Ni. That is, the part to be observed is recorded reliably at the center of the recording surface, and there is no possibility that it will deviate from the recording range w.

As mentioned above, the apparatus of the present invention uses a servo mechanism to adjust the temperature difference between the sample and a reference temperature point, such as a standard sample, by the servo mechanism only during the period of rapid IS change immediately after the furnace temperature starts to change. The compensation value is fixed at the point when the temperature difference becomes stable. Therefore, it eliminates the possibility that the recording of the part to be observed will be lost due to fluctuations in the baseline. It is extremely effective for the measurement of You can also do it.

[Brief explanation of drawings]

FIG. 1 shows the configuration of an embodiment of the present invention. The second factor is a diagram illustrating the operation of the apparatus of the present invention. In the figure, l indicates the furnace, 2Fi sample, 3Fi standard sample, 4. Contact point of Ilt Iri differential thermal turtle pair, 10g automatic recorder, 16 is potentiometer, 1) is slider, 19 is servo motor, 1alVi timer low-couple/ml

Claims (1)

[Claims] Each of the two contacts is connected to the sample and the reference temperature point (the output end of the differential thermocouple attached to each and the output end of the variable potency date meter are connected to the input end of the differential operational amplifier (=each via an input resistor, and the output end of the operational amplifier is connected to the input end of a recorder and a servo amplifier, and the drive motor of the slider of the variable potentiometer is connected to the output end of the servo amplifier, and the input circuit of the C2 motor is connected to the output end of the servo amplifier. Zero-point mm device for automatic recording thermal analysis, characterized in that it is equipped with a switch for opening at four desired observation temperatures.