JP2500716B2 - TOC meter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TOC meter for measuring TOC (total organic carbon) in a sample.

[0002]

2. Description of the Related Art A TOC meter includes a carrier gas supply unit, a sample injection unit, a combustion oxidation reaction unit, and a CO ₂ detection unit, and measures a TOC value in a sample and outputs an analog signal corresponding to the TOC value. There is a total. Some TOC meters have a function of measuring and automatically calibrating a standard solution at a predetermined cycle and outputting an analog signal corresponding to the TOC value of a sample. Such TOC
In the meter, the TOC value of the sample is obtained by calibration with the latest standard solution, and the standard solution is automatically calibrated (automatically calibrated sensitivity), and the next standard solution is measured and output as an analog signal. If the span standard solution is adjusted to the full scale of the output of the recorder, the output will shake the full scale of the recorder when the sensitivity changes to the + side, and the recorded value cannot be read by the recorder. In order to prevent such an inconvenience, a span standard solution having a lower concentration than the full scale, for example, a concentration of 80% of the full scale is used.

[0003]

Since the output signal of the standard solution measurement value is the measurement value in the state in which it was previously automatically calibrated,
It is difficult to determine how much the TOC meter sensitivity change has occurred since the first calibration. When a span standard solution with a concentration smaller than the full scale value of the recorder is used, the range between the span standard solution concentration and the full scale value is the uncalibrated region. For example, with a TOC meter with a full scale of 100 ppm, 80 pp
When calibrated with the standard solution of m, the range of 80 to 100 ppm becomes an uncalibrated region. An object of the present invention is to provide a TOC meter in which the state of sensitivity change from the start of measurement can be understood and which is calibrated with a standard solution to a full scale concentration.

[0004]

The present invention will be described with reference to FIG. The measurement control unit 1 is provided to control the measurement operation so as to measure the standard solution in each predetermined cycle,
An initial calibration value memory 3 for storing the first standard solution measurement value and a latest calibration value memory 4 for storing the latest standard solution measurement value are provided. The TOC calculation unit 5 calculates the TOC value from the measured value of the sample using the calibration value of the latest calibration value memory 4. The analog output unit 10 adjusts the full scale of the analog signal to the value of the latest span standard solution when measuring the sample, and sets it to a position within the range of 70% to 95% of the full scale when measuring the span standard solution. Also outputs the span standard solution measurement values from the second time onward based on the solution output value.

[0005]

[Function] The sample measured value is measured in the calibrated state after each automatic calibration and is output as an analog signal. However, the standard solution measured value is output in the uncalibrated state. You can see the change. Use a span standard solution with a full-scale concentration. When it is output to the recorder as an analog output, it is output as a value in the range of 70 to 95% of full scale, and it is prevented from swinging out of the full scale of the recorder even when the sensitivity changes to the + side.

[0006]

FIG. 2 is a block diagram showing a configuration for realizing the control system of FIG. The output of the detection unit 2 is captured by the MPU (microprocessor unit) 7, and the automatically calibrated sample measurement value and the standard solution measurement value after the second measurement are output from the analog output unit 10 as analog signals. A memory 8 such as a RAM for temporarily storing the standard solution measurement value is connected to the MPU 7. The measurement control unit 1, the calibration value memories 3 and 4 and the TOC calculation unit 5 in FIG.
It is realized by the MPU 7 and the memory 8.

FIG. 3 shows a TOC meter of one embodiment. The sample flows into the flow-type sample container 12 from the lower inlet, and is discharged from the upper outlet. The sample in the sample container 12 is stored in the sample
, A certain amount is collected and switched to the TC reaction unit 16 or the IC reaction unit 18 for guiding. The TC reaction section 16 is provided with a TC combustion tube filled with an oxidation catalyst, and a heating furnace is provided outside the TC combustion tube to heat the TC combustion tube. Pure oxygen gas or high-purity air excluding CO ₂ and hydrocarbons is supplied from the carrier gas supply unit 20 to the TC reaction unit 16 at a controlled gas flow rate as a carrier gas.
In the TC reaction unit 16, all the carbon components in the supplied sample are converted into CO ₂ gas, which is led to the measurement cell of the non-dispersive infrared gas analyzer (NDIR) 22 of the CO ₂ detection unit and detected. In the IC reaction unit 18, inorganic carbon is generated as CO ₂ gas, and is guided to the measurement cell of the NDIR 22 together with the carrier gas and detected. The sample injection part 14 is TC or IC
The standard solution 23 can also be injected for preparing (calibrating) the calibration curve.

In order to process the detected value of the NDIR 22,
As shown in FIG. 2, an MPU 7 is provided, and the MPU 7 calculates the TOC value from the TC value and the IC value, and connects the analog output unit 10 to the MPU 7 to output the TOC value to the recorder. Have been. Reference numeral 26 denotes a measured value display / printing unit for displaying and printing measured values.

The operation of one embodiment will be described with reference to the flowchart of FIG. 4 and the output example of the recorder of FIG. Simultaneously with the start of measurement, the analog output value is set to 0 (step S1).
The analog output value is held in the memory until it is recalculated in step S8 or S9, and the value is stored in step S7.
The analog signal is output by. When the first calibration is completed (steps S2 and S3), the standard solution measured value is stored in the latest calibration value memory 4 (stored value is B) (step S).
4). Since this is the first standard solution measurement, it is also stored in the first calibration value memory 3 (stored value is A) (step S
5, S6). Here, since the analog output value is not calculated, the analog output value set to 0 in step S1 continues to be output in step S7. This state is the state shown as in FIG.

Each time the measurement of the sample is completed, the procedure advances to step S9 through steps S2 and S3, and the calibration value B stored in the latest calibration value memory 4 is set to full scale,
The analog output value is calculated based on this, and step S
The value is output at 7. This state is the state shown as in FIG. When the second calibration is performed, the measured value is stored in the latest calibration value memory 4 in steps S4 through S4 and the calibration value B is updated to the latest value (step S5), and then in step S8. The first span standard solution measurement value A is set to 0.8 of full scale, and the analog output value of the latest span standard solution is calculated based on it (step S8), and this value is output (step S).
7). This state is the state shown as in FIG. It shows that there is almost no change in sensitivity during the second calibration. During calibration, the standard solution is measured, for example, three times, and the sensitivity of the TOC meter is calibrated from the average value. In the sample measurement after the second calibration is performed, the TOC concentration is calculated from the measured value based on the calibration value B of the latest calibration value memory 4 and output as an analog signal. This state is the state shown as in FIG. After that, the calibration and the sample measurement are repeated in the same manner. In the example of FIG. 5, it can be seen that the sensitivity is lowered for some reason during the third calibration.

In the example of FIG. 5, the span value at the time of initial calibration is set to 80% of the full scale of the recorder, but this is an example, and it may be set to another appropriate value. In addition, although an example in which the present invention is applied to a calibration method using only the span standard solution is shown in the examples, when the calibration is performed using two points, that is, a zero point and a span point, the span point is the same as above. By using the method, the measured value of the zero standard solution can be adjusted to, for example, 20% of full scale so that the sensitivity can be recognized even when the sensitivity changes in the negative direction.

[0012]

In the present invention, the output signal of the sample measured value is output as a value calibrated by automatic calibration every time, but the output of the standard solution measured value is output in the uncalibrated state, so The sensitivity change from the start point and the zero point change in the case of two-point calibration can be easily seen. Since the full-scale value and the span standard solution concentration match, the sample measurement is performed using the range confirmed with the standard solution.
Higher measurement reliability. In addition, it is possible to prevent mistakes such as making a mistake in the concentration of the span standard solution.

[Brief description of drawings]

FIG. 1 is a block diagram showing the present invention.

FIG. 2 is a block diagram showing a configuration for realizing FIG. 1;

FIG. 3 is a configuration diagram showing a TOC meter according to one embodiment.

FIG. 4 is a flowchart illustrating the operation of one embodiment.

FIG. 5 is a waveform diagram recorded in the recorder as a result of the operation of the embodiment.

[Explanation of symbols]

 1 Measurement control unit 2 Detection unit 3 Initial calibration value memory A 4 Latest calibration value memory B 5 TOC calculation unit 7 MPU 8 Memory 10 Analog output unit

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Hiroaki Matsuhisa, Hiroaki Matsuhisa, No. 1 Kuwabara-cho, Nishinokyo, Nakagyo-ku, Kyoto-shi, Shimadzu Corporation Sanjo Plant (56) References JP-A-2-91569 (JP, A)

Claims (1)

(57) [Claims] 1. A TOC meter for measuring a TOC value in a sample, which comprises a carrier gas supply section, a sample injection section, a combustion oxidation reaction section and a CO ₂ detection section, and which outputs an analog signal corresponding to the TOC value, A measurement control unit that controls the measurement operation so as to measure the standard solution at each predetermined cycle,
The initial calibration value memory that stores the first standard solution measurement value, the latest calibration value memory that stores the latest standard solution measurement value, and the calibration value of the latest calibration value memory from the sample measurement value
The TOC calculator that calculates the OC value and the full scale of the analog signal are adjusted to the latest span standard solution value when measuring the sample, and 70% of the full scale when measuring the span standard solution.
To 95%, and a TOC meter that has an analog output section that also outputs the span standard solution measured value from the second time onward based on the first span standard solution output value.