JPH04125473A - Filament-life prediction device - Google Patents

Abstract

PURPOSE:To enable life to be predicted by setting a target threshold of life and by calculating filament current ratio from the detection filament current and setting initial value. CONSTITUTION:A filament current Ii and an integral value Ti of current- conduction time for the filament are measured at a filament current detection part 14 and by a total current-conduction time 16, respectively. Also, an initial value Imax of filament current and target threshold Rsh of life are set previously at a setting part 18. Then, a filament current ratio calculation part 20 calculates a filament current ratio Ri from the current Ii and the initial value Imax. Then, an operation part 24 determines time ratio corresponding to a current ratio Ri according to a characteristic curve and the current ratio Ri of change with time of filament current which are stored in a memory 22. Then, remaining time required before the current ratio Ri reaches the threshold Rsh is calculated from this time ratio and the integral time value Ti, thus enabling filament life to be predicted.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an apparatus for predicting the lifespan of a filament used when ionizing a gas sample using thermoelectrons.

<Conventional technology> Conventionally, for example, in a gas chromatograph mass spectrometer,
A gas sample whose components have been separated using a gas chromatograph is guided into an ionization chamber, where it is ionized by collision with thermionic electrons generated from a filament, and the ionized sample is mass-separated using a mass spectrometer to identify the component elements contained in the sample. analysis.

In this case, in order to achieve stable ionization, the filament current is usually controlled so that the amount of hot electrons reaching the trap is constant. In other words, the material in the filament gradually evaporates as it is heated, becoming thinner over time, and correspondingly, it becomes easier to emit thermoelectrons.
The filament current is controlled to gradually decrease over time. Even if the filament current is controlled in this way, the filament itself gradually becomes thinner and eventually melts and breaks. Therefore, the filament has its own lifespan, but the lifespan of the filament depends on the type of sample to be analyzed, the analysis conditions, the material of the filament, etc., and is not necessarily uniform.

On the other hand, it usually takes tens of minutes to several hours to analyze one sample using a gas chromatograph mass spectrometer, but if the filament reaches the end of its life and breaks during such an analysis, The analysis of the sample must be re-analyzed from the beginning, which takes time and effort. In addition, some samples cannot be re-analyzed if there are only a few samples. Therefore, predicting filament life is important.

In the prior art, the filament current is monitored using an ammeter or the like, and when the filament current drops below a preset threshold, the filament is considered to have reached the end of its life and is replaced.

<Problem to be solved by the invention> However, just by monitoring the filament current and comparing it with a threshold as in the past, it is not possible to equally predict how long the filament can be used in the future. . Therefore, the problem of filament breakage during analysis still remains unsolved.

Means for Solving the Problems The present invention has been made in view of the above circumstances, and is intended to make it possible to predict the time from the present moment until the filament reaches its end of life.

Therefore, the filament life prediction device according to the first invention includes a filament current detection section that detects the filament current Ii, an integrating time meter that integrates the energization time to the filament and outputs the integrated time Tt, and an initial value of the filament current. A setting section that sets I max and a threshold value Rsh that is a guideline for filament life, and a filament current I detected by a filament current and current detection section.
a filament current ratio calculating section that calculates the filament current ratio Ri (=Ii/I max) from i and the initial value 1 max set in the setting section; A time ratio ti corresponding to the filament current ratio Ri is determined based on a memory in which a characteristic curve obtained from the above is stored in advance and the characteristic curve stored in this memory, and this time ratio ti and the integrated time Tt are The present invention includes an arithmetic unit that calculates the remaining time T++ required for the filament current ratio R4 to reach the threshold value Rsh, and an output unit such as a printer or a display that outputs the arithmetic result Tr of this arithmetic unit. .

The filament life prediction device according to the second invention includes a filament current detection section that detects the filament current Ii, a setting section that sets the initial value 1 maX of the filament current and a threshold value Rsh that is a guideline for the filament life, respectively; The filament current Ii detected by the filament current detection section and the initial value I max set in the setting section
and filament current ratio Ri (=Ii/1 max
), a slope calculation unit that calculates the change slope k per unit time of this filament current ratio Ri, the change slope k calculated by this slope calculation unit, the threshold value Rsh and Filament current ratio R
The filament current ratio Ri from each point of i is the threshold value R
The computer includes an arithmetic unit that calculates the remaining time Tr2 required to reach sh, and an output unit such as a printer or a display that outputs the arithmetic result Tr2 of this arithmetic unit.

<Operation> In the filament life prediction device according to the first invention, the filament current Ii is measured by the filament current detection section, and the integrated value Tt of the current application time to the filament is measured by the integrated time meter. Further, the initial value I max of the filament current and the threshold value Rsh are set in advance by the setting section. The filament current ratio calculation section calculates a filament current ratio Ri (-I i /Imax) from the filament current Ii and its initial value 1 max, and sends it to the calculation section. Further, the cumulative time Tt is also sent to the calculation section.

The calculation unit calculates, from the characteristic curve of the filament current change over time stored in the memory and the filament current ratio Ri,
A time ratio t+ corresponding to the filament current ratio R4 is determined, and then a remaining time Tr+ required for the filament current ratio Ri to reach the threshold value Rsh is calculated from this time ratio ti and the integrated time Tt. This calculation result Tr+ is then output to the output section.

In the configuration according to the second invention, the filament current ■i is detected by the filament current detection section. Further, the initial value I max of the filament current and the threshold value Rsh are set in advance by the setting unit. filament current ratio calculation section,
is the filament current Ii and its initial value I max
and filament current ratio R4 (-I i/I ma
x) and sends it to the gradient calculation unit and calculation unit, respectively. The gradient calculation section calculates a change gradient k of the filament current ratio Ri per unit time, and sends this to the calculation section.

The calculation unit calculates the remaining time T required for the filament current ratio Ri to reach the threshold value Rsh from the above-mentioned change slope k, threshold value Rsh, and filament current ratio Ri.
r! Calculate. This calculation result Trt is then output to the output section.

In this way, in both the first and second inventions, the remaining time T r
+, Trs is output, so this remaining time Tr1,
Trs can be determined as the period from the current moment until the end of the filament's life.

<Examples> Example 1 FIG. 1 is a block diagram of a filament life prediction device according to an example of the first invention.

In the figure, ■ is an ion source, which consists of an ionization chamber 2 into which a gas sample is introduced, a filament 4 that emits thermionic electrons, a trap 6 that receives thermionic electrons that have passed through the ionization chamber 2, and a lens 8 for focusing ions. . IO is a filament heating control circuit that controls the filament current flowing through the filament 4 based on the electron current obtained by receiving thermoelectrons in the trap 6.

12 shows the entire filament life prediction device, 14 a filament current detection unit that detects the filament current Ii output from the filament heating control circuit IO, and 16
is an integrating time meter that integrates the current application time to the filament 4 and outputs the integrated time Tt.

Reference numeral 18 denotes a setting unit for setting an initial value I max of the filament current value obtained when the filament 4 is first turned on, and a threshold value Rsh serving as a guide for the filament life. 20 is a filament current ratio calculation unit that calculates a filament current ratio Ri (=Ii/Imax) from the filament current Ii detected by the filament current detection unit 14 and the initial value Imax set by the setting unit 18. .

22 is a memory in which a characteristic curve C obtained by normalizing the change in filament current over time on both the vertical and horizontal axes is stored in advance. In other words, the lifetime of the filament 4 until it melts depends on the type of sample to be analyzed, the analysis conditions, the material of the filament, etc., and is not necessarily uniform. If the time ratio corresponding to the ratio threshold value Rsh is taken as 1 and plotted on the horizontal axis, then the change over time of the filament current will have a tendency as shown in FIG. 2. Therefore, this characteristic curve C is stored in the memory 22.

24 determines a time ratio ti corresponding to the filament current ratio R4 based on the data of the characteristic curve C stored in the memory 22, and determines that the filament current ratio Ri is a threshold value from this time ratio ti and the integrated time Tt. Value Rs
A calculation section 26 calculates the remaining time Tr+ required to reach h, and 26 is an output section (in this example, a display) that outputs the calculation result of the calculation section 24.

Next, the operation of the above configuration will be explained.

The filament heating control circuit 10 feedback-controls the filament current Ii flowing through the filament 4 based on the value of the electron current obtained by receiving thermoelectrons from the filament 4 in the trap 6. The filament current (1) at this time is detected by the filament current detection section 14. In this control, the material of the filament 4 gradually evaporates due to heating and becomes thinner over time, and correspondingly, it becomes easier to emit thermoelectrons. Therefore, the filament current Ii is The maximum value I max is taken at 1, and gradually decreases as time passes.Furthermore, while the filament heating control circuit 10 is operating and heating the filament 4, the integrated value Tt of the energization time is calculated by the integrated time meter 16. be measured.

On the other hand, the maximum value of the filament current obtained when the filament 4 is first turned on is measured in advance, this maximum value is set as the initial value 1 max, and the setting unit 18 sends the filament current ratio detection unit 20 to the filament current ratio detection unit 20. Send. Also,
When the filament current ratio is, for example, 0.85 when the initial value I max is 1, it is set as the threshold value Rsh, and the threshold value Rsh is sent from the setting section 18 to the calculation section 2.
Give to 4.

The filament current ratio calculating section 20 sequentially calculates the filament current ratio Ri (=Ii/I max) from the filament current Ii and its initial value 1 max, and sends it to the calculation section 24 . Further, the cumulative time Tt obtained by the cumulative time meter 16 is also sent to the calculation section 24 .

The calculation unit 24 calculates the characteristic curve S of the filament current change over time and the filament current ratio R stored in the memory 22.
From i, a time ratio ti corresponding to the filament current ratio Ri is determined. That is, once the filament current ratio Ri is known, the time ratio ti corresponding to this filament current ratio Ri is uniquely determined from the characteristic curve C in FIG. The remaining time Tr+ required for the filament current ratio Ri to reach the threshold value Rsh from the integrated time Tt is calculated as Tr, -Tt·(1/Ii-1) (1).

That is, if the cumulative time corresponding to the time ratio ti is Tt, the cumulative time T when the time ratio corresponding to the threshold value Rsh is 1 is T=Tt/li, and therefore, the current filament current ratio Ri The remaining time Tr+ until reaching the threshold value Rsh is Tr,=T-Tt=Tt/
Since Ii-Tt = Tt·(1/l+-1) and formula (1) is obtained, the remaining time Tr+ is calculated based on this formula (1). This calculation result Tr+ is then displayed on the display 26.

Therefore, the remaining time Tr+ displayed on the display 26 can be determined as the time from the current time until the filament reaches the end of its life.

Embodiment 2 FIG. 3 is a block diagram of a filament life prediction device according to an embodiment of the second invention, and parts corresponding to those in FIG. 1 are given the same reference numerals.

In FIG. 3, 14 is a filament current detection section, 18
20 is a setting section, 20 is a filament current ratio calculation section, and 26 is a display, and since these structures are the same as in the first embodiment, their explanations will be omitted.

In addition, in this embodiment, an integrating time meter 1 like in embodiment 1 is used.
6 and memory 22 are not provided, and instead, a gradient calculation unit 23 that calculates a change gradient k per unit time T of the filament current ratio Ri calculated by the filament current ratio calculation unit 20, The filament current ratio Ri is the threshold value Rsh from each of the change slope k calculated by the calculation unit 23, the filament current ratio Ri1 calculated by the filament current ratio calculation unit 20, and the threshold value R8h preset by the setting unit 18. The remaining time T required to reach
It also includes a calculation unit 25 that calculates rt.

Next, the operation of the above configuration will be explained.

Filament current Ii is detected by filament current detection section 14. Further, the initial value I max of the filament current is set in advance by the setting unit 18 . Further, a threshold value Rsh is set when the filament current ratio becomes, for example, 0.85 when the initial value 1 max is set to 1, and the threshold value Rsh is provided from the setting section 18 to the calculation section 24 . The filament current ratio calculation section 20 calculates the filament current ratio Ri (=1 i/I max) from the filament current Ii and its initial value I max, and sends this to the calculation section 25 and the gradient calculation section 23, respectively. .

As shown in FIG. 4, the gradient calculation unit 23 calculates the current filament current ratio Ri and the unit time ΔT using this as a base point.
Saw I3 Calculate the change gradient k of the filament current ratio per unit time ΔT from the previous filament current ratio Ri + at the time of going back, as k = (Ri − Ri 1)/ΔT, and use this as It is sent to the calculation unit 25.

The calculation unit 25 calculates the remaining time Tr2 until the filament current ratio Ri reaches a preset threshold value Rsh from each of the L threshold value Rsh and the filament current ratio Ri to the above-mentioned change gradient. )/k (2)
Calculated as

That is, in FIG. 4, the cumulative time of the filament 4 is Tt, and the straight line (gradient k) at the cumulative time tjlTt.
Let D be the value of the intercept that intersects with the vertical axis of R4= -Tt
Since the relationship +D holds true, D=Ri- -Tt On the other hand, if T is the cumulative time corresponding to the threshold value Rsh, then the following equation holds true.

Rsh=-T+D=-T+Ri-Tt Therefore, T=-(Rt-Rsh)/+Tt Therefore, the remaining time Tr required for the current filament current ratio Ri to reach the threshold value Rsh is: Since Trz=T-Tt=-(Ri-Rsh)/, equation (2) is obtained, the remaining time Tr is calculated based on equation (2). Then, this calculation result Tr
t is displayed on the display 26.

Therefore, the remaining time Tr displayed on the display 26 can be determined as the time from the current time until the filament reaches the end of its life.

<Effects of the Invention> According to the present invention, it is possible to predict the remaining time until the filament reaches the end of its life from the present time, so if the remaining time is longer than the time required to analyze the sample, analysis can be performed; If it is short, you can make decisions such as replacing the filament before analysis. therefore,
Since it is possible to avoid redoing the analysis, etc., the efficiency of the analysis can be improved.

This is particularly useful in online automatic analysis, etc., since it allows determining when to replace the filament when analyzing samples one after another.

In particular, in the second invention, the filament current ratio R
Since the slope of change k per unit time of i is calculated, even if the characteristic curve of the change over time of the filament current changes somewhat due to the influence of subsequent analysis conditions, it is possible to determine the appropriate filament life accordingly. It has the advantage of being predictable.

[Brief explanation of drawings]

The drawings show embodiments of the present invention, and FIG. 1 is a block diagram of a filament life prediction device according to the embodiment of the first invention, and FIG. 2 is an explanatory diagram for predicting filament life.
FIG. 3 is a block diagram of a filament life prediction device according to an embodiment of the second invention, and FIG. 4 is an explanatory diagram for predicting filament life. 4... Filament, 12... Filament life prediction device, 14... Filament current detection unit, 16...
- Integrating time meter, 20... filament current ratio calculation unit,
22...Memory, 23...Gradient calculation unit, 24.25
...Arithmetic unit, 26...Display unit.

Claims (2)

[Claims] (1) Filament current detection unit (14) that detects the filament current Ii flowing through the filament (4)
and an integrating time meter (16) that integrates the energization time for the filament (4) and outputs the integrated time Tt, an initial value Imax of the filament current, and a threshold value Rsh that is a guide to the filament life. Setting section (18
), and the filament current ratio Ri (=Ii/
A filament current ratio calculation unit (20
) and a memory in which the characteristic curve obtained by normalizing the change in filament current over time on both the vertical and horizontal axes is stored in advance (22)
And, based on the characteristic curve stored in this memory (22),
A calculation for determining a time ratio ti corresponding to the filament current ratio Ri, and calculating the remaining time Tr_1 required until the current filament current ratio Ri reaches the threshold value Rsh from this time ratio ti and the integrated time Tt. Department (
24); and an output section (26) such as a printer or a display that outputs the calculation result Tr_1 of the calculation section (24). (2) Filament current detection unit (14) that detects the filament current Ii flowing through the filament (4)
, a setting section (18) for setting the initial value Imax of the filament current and a threshold value Rsh serving as a guide for the filament life, respectively; and a setting section (18) for setting the filament current Ii detected by the filament current detection section (14) and the setting section ( From the initial value Imax set in 18), the filament current ratio Ri (=Ii/Im
ax); a slope calculation unit (23) that calculates the change gradient k per unit time of this filament current ratio Ri; The change slope k, the threshold value Rsh
and a calculation unit (25) that calculates the remaining time Tr_2 required for the filament current ratio Ri to reach the threshold value Rsh from each value of the filament current ratio Ri, and outputs the calculation result Tr_2 of the calculation unit (24). A filament life prediction device comprising: an output unit (26) such as a printer, display, etc.