JPH0116371B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a differential thermal balance. More specifically, the present invention relates to a horizontal differential thermal balance with little measurement error.

Conventionally, in a horizontal differential thermal balance, heating is carried out by placing a sample on one end of the balance beam and inserting the sample into a heating furnace. FIG. 1 shows a schematic diagram of a basic horizontal differential thermal balance when there is only one balance beam. When the sample 5 in the container 4 loses or increases in weight due to the heat of the heating furnace 3, the sample balance beam 1 tilts. This is detected using the lamp 8, the shutter 9, and the photocell 10, and the change in the photocell signal is amplified by the power amplifier 11, and a current i is applied to the feedback coil 7 so that the photocell signal is balanced.
is controlled to keep beam 1 horizontal.
Since this current i corresponds to the weight change of the sample, it is measured by the current measuring section 12 and recorded by the recorder 1.
5, the change in weight of the sample can be measured.

However, in the case of a single balance beam as described above, beam 1 thermally expands due to temperature rise, and the fulcrum
There were disadvantages in that the length l between the points changed, causing a drift due to the fluctuation of the moment, and furthermore, the balance sensitivity changed. Furthermore, what is meant by drift here?
This is a phenomenon in which the moment of the beam itself changes due to a change in the balance beam length, and the balance output is generated or changed, and corresponds to so-called zero point fluctuation or baseline fluctuation. On the other hand, a change in balance sensitivity refers to a phenomenon in which the contribution rate of sample weight fluctuation to the balance output changes due to a change in the balance beam length.

Therefore, a reference balance beam with an empty container placed on a beam with the same mechanism as the sample balance beam was inserted into the same heating furnace and differentially connected to the sample balance beam, and the output signals of the two balance beams were A differential thermobalance that takes the difference between the two has been proposed and is in use. However, in this case, although the drift due to the moment variation can be canceled by the reference side, the sensitivity change cannot be canceled.

The present invention has been made to solve these problems, and provides a differential thermal balance that not only cancels drift but also measures while continuously correcting the sensitivity of the balance beam.

This invention continuously measures changes in the weight of the sample while canceling drift by inserting two sets of balance beams, one for the sample and one for reference, into a single heating furnace and measuring the difference in the output of these two sets of balance beams. In a horizontal type differential thermal balance, a variable amplification amplifier is provided to control the balance output on the sample side based on the balance output on the reference side, and the sensitivity is continuously corrected.

Hereinafter, the present invention will be described in detail based on the accompanying drawings.

FIG. 2 is a schematic diagram showing a specific example of the differential thermal balance of the present invention. In FIG. 2, the differential thermal balance consists of a sample balance beam 1 and a reference balance beam 2, which are formed by inserting the tips of the containers 4 in parallel into a heating furnace 3. is lamp 8, shutter 9, photocell 1
0, power amplifier 11, current measuring section 12 and 1
2' is attached. Then, the variable amplification differential amplifier 13 reduces the reference side balance output (current value) to cancel the drift, and the sample side balance output from which the drift has been canceled can be further controlled by the reference side balance output. The current measurement units 12 and 12' are connected to each other. In addition, 6 is a counterweight, 7 is a feedback coil, 14 is a function generator that sets the amplification factor of the amplifier 13, 15 is a recorder, and 16 is a
indicates a carrier gas flow path for removing generated gas.

The function of the differential thermal balance with the above configuration will be explained.
First, the change in length l due to temperature rise of the reference balance beam is investigated, and the function generator is configured to output the amplification factor setting input to the variable amplification factor differential amplifier 13 based on the relationship with the corresponding balance output. Adjust 14. Specifically, for example, if the beam length l increases by Δl due to temperature rise and changes to (l + Δl), the balance sensitivity will change and a measured value that is (l + Δl)/l times the actual value will be obtained. In order to correct the elongation, the elongation is detected using the balance output (current i), and based on this, l/
Adjustment is made so that an amplification factor of (l+Δl) can be set.

After the above adjustment, the sample 5 is introduced into the container 4 and heated by the heating furnace 3. As mentioned above, the sample balance beam 1 is tilted due to the weight loss of the sample caused by heating and the elongation of the balance beam length l. A current i flows through the yield back coil 7. On the other hand, on the reference side, the reference balance beam 2 is tilted due to the elongation of the beam length l due to heating, and a current i' similarly flows. The variable amplification differential amplifier 13 first outputs the balance output i on the sample side.
The sample-side balance output (i-i') is set by subtracting the reference-side balance output i' from the reference-side balance output (i-i'), which cancels the drift, and is further amplified by the functions of 13 and 14 in accordance with the reference-side balance output i. l/(l+
Δl) times] and the final output is output to the recorder 15.
recorded in

In this invention, the amplification factor variable differential amplifier 13
It may be an analog amplifier or a microcomputer, as long as it has at least the differential function and control function as described above. Note that it is preferable to use a microcomputer because it eliminates the need for a control input setting device such as the function generator 14 and simplifies the circuit.

The differential thermobalance of this invention eliminates the influence on measured values due to the expansion of the balance beam during sample heating, which is the biggest problem with horizontal thermobalances, reducing measurement errors and requiring high precision and accuracy. It can be suitably used for measurements that are carried out.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of a conventional horizontal type differential thermal balance. FIG. 2 is a schematic diagram showing a specific example of the differential thermal balance of the present invention. 1... Balance beam for sample, 2... Balance beam for reference, 3... Heating furnace, 4... Container, 5... Sample,
6... Counterweight, 7... Feedback coil, 8... Lamp, 9... Shutter, 1
0...Photo cell, 11...Power amplifier, 1
2, 12'...Current measuring section, 13...Variable gain amplifier, 14...Function generator, 15...Recorder, 16...Carrier gas flow path.

Claims (1)

[Claims] 1. Two sets of balance beams of the same length, one for sample and one for reference, are inserted into one heating furnace and the difference in the output of these two sets of balances is taken to cancel the drift and change the weight of the sample. In a horizontal type differential thermal balance that continuously measures : l/l+Δl (In the formula, l is the balance beam length, and Δl is the increase in the balance beam length during temperature rise determined by the balance output on the reference side). A differential thermal balance, characterized in that it is configured to correct balance sensitivity.