JPS598164Y2 - radiation thickness gauge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radiation thickness meter that measures the thickness of an object to be measured from the amount of radiation beam that has interacted with the object, and particularly to a calibration device for a radiation thickness meter.

Radiation thickness gauges are calibrated so that there is linearity between the measured thickness and the actual thickness.

That is, in the conventional radiation thickness meter, the relationship between the thickness of the object to be measured and the output of the preamplifier becomes as shown in FIG. 3C as the thickness increases, due to the influence of scattered radiation.

In order to reduce the setting error, it is necessary to match the characteristics of the set thickness value and set voltage in the setting circuit to those shown in FIG. 3D.

However, in reality, this is difficult.

For this reason, the relationship between the set thickness value of the setting circuit and the set voltage is made a linear function, and the detection signal level before logarithmic conversion can be shifted using the shift voltage generation circuit. Calibrating the meter.

When the thickness is zero, the indicator on the thickness gauge is adjusted so that it shows zero, and when calibrating the maximum thickness, the shift voltage generation circuit is adjusted so that the indicator shows zero, and calibration is performed at two points. was.

However, since calibration is performed only at the thickness O and the maximum thickness, the relationship between the error and the measured thickness may show significant nonlinearity, as shown in curve A in Figure 1, due to nonlinearity of the amplifier in the process. Ta.

The present invention was developed to eliminate the above-mentioned drawbacks, and an object of the present invention is to provide a radiation thickness meter with improved linearity of measured values.

The purpose of this invention is to compare the electrically converted signal of the amount of radiation beam transmitted or scattered through the object to be measured with a separately given set value, find the deviation, and calculate the measured thickness from the set value and the deviation value. A radiation thickness meter comprising a measurement system for measuring the measured thickness, and a calibration system that has a reference sample in the radiation beam path for calibrating the measured thickness and supplies a calibration signal corresponding to the thickness to the measurement system as a calibration setting value. , the calibration system comprises at least one auxiliary sample in the radiation beam path for calibrating the intermediate thickness, and a calibration signal corresponding to the auxiliary sample thickness is provided to the measurement system as a calibration set point. .

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 2 is an explanatory diagram of an embodiment of the present invention, and as described above, the structure is roughly divided into a measurement system and a calibration system.

Furthermore, the measurement system is further divided into a radiation system and an electronic circuit system.

The radiation system is for irradiating radiation onto the measurement object 13 and detecting the amount of radiation that has passed through the radiation source 10.
, a detector 14 such as an ionization chamber.

In addition, a shutter 11 and two samples 12 and 12' for calibration are provided in the path of the radiation beam,
It is controlled by a control device 15.

Conventionally, only one sample having a thickness equal to the maximum measured thickness was used.

The electronic circuit system converts the electrical output signal of the detector 14 into a predetermined signal, and includes a preamplifier 21 and a zero adjustment amplifier 2.
2, logarithmic amplifier 23, calibration amplifier 24, comparison amplifier 25
It is constructed with the following.

The calibration system includes a measurement setting device 40, a calibration setting device 42, a calibration switch 30 that cooperates with the control device 15 of the measurement system, and a buffer amplifier 26.

Of the contacts ae to a5 of the calibration switch 30, a1 is used for measurement, a2 and a3 are used for zero point adjustment, and a4 and a5 are used for calibration.

These contacts are switched in sequence to adjust the corresponding adjustment points.

Hereinafter, the operation of the embodiment of the present invention will be explained according to the measurement preparation operation.

(1) Position the switch 30 at contact a2.

At this time, since there is no setting input to the comparator amplifier 25, the measurement input is also set to zero, so that no comparison deviation output is produced.

That is, the variable resistor 21b is adjusted so that the output of the amplifier 21 becomes zero when the shutter 11 is closed.

(2) Next, open the shirt cover 11 and use the calibration sample 12.
．． 12' and the object to be measured 13 are not in the radiation beam, that is, the thickness is zero, switch the contact point to a3, and adjust the variable resistor 22a so that the output of the preamplifier 21 becomes a predetermined value (for example, 10■). .

At this time, the output of the shift voltage generator 22b is adjusted to zero in advance.

Further, the logarithmic amplifier 23 is also set in advance so that the output is zero when the input is 10.

In this way, when the output of the amplifier 21 becomes 10 volts, the output of the calibration amplifier 24 becomes 0 volts, and the output of the buffer amplifier 26 becomes 0 volts.
Since the output of is also zero, the deviation indicator (not shown) on the output side of the comparator amplifier 25 becomes zero.

That is, in this process, the variable resistor 22a is adjusted so that the pointer of the deviation indicator becomes zero (3) Furthermore, the switch 30 is switched to contact a4, and the sample 12 with the maximum thickness is inserted into the radiation beam path. I'll do what I do.

At this time, a set voltage corresponding to the thickness of the sample 12 is supplied from the setter 42 to the buffer amplifier 26.

Here, a deviation indicator (
variable resistor 24 a so that the indication of
Adjust.

(4) Switch to contact a5 of the calibration switch 30 and insert the sample 12' with the maximum thickness into the radiation beam path.

At this time, a set voltage corresponding to the thickness of the sample 12' is supplied from the setter 42 to the buffer amplifier 26.

Here, if the deviation indicator (not shown) on the output side of the comparator amplifier 25 is outside the allowable range, the shift voltage generator 22b is adjusted so that the indicator becomes zero.

(5) Repeat operations (3) and (4) until the desired calibration accuracy is achieved.

By the above operations, conventionally the two points a, l) in Fig. 1 are
A characteristic curve such as curve A was obtained corresponding to the above, but it is now possible to obtain a characteristic curve superior to the conventional one such as curve B corresponding to the three points a, b, and c.

By increasing the number of calibration points as described above, the present invention can provide a radiation thickness meter with excellent linearity of measured values.

In addition, in the present invention, many modifications other than the above-mentioned embodiments can be considered, but the main ones are listed as follows.

(a) Calibration sample 12' is approximately ÷ of calibration sample 12.
(b) The number of calibration samples is three or more; (c) The deviation output of the comparison amplifier 25 is not used, and the amplifier (2) The deviation output of the comparison amplifier 25 is amplified by a servo amplifier to automate each adjustment.

[Brief explanation of drawings]

FIG. 1 is an output characteristic diagram of the radiation thickness meter, FIG. 2 is an explanatory diagram of the embodiment of the present invention, and FIG. 3 is an explanatory diagram of the operation of the embodiment of the present invention. 10...radiation source, 11...shaft, 12.12'...sample, 13...
・Object to be measured, 14...Detector, 15...
...Control device, 21...Preamplifier, 22...
...Zero-tune amplifier, 23 ... Logarithmic amplifier, 2
4... Calibration amplifier, 25... Comparison amplifier, 26... Buffer amplifier, 30...
・Switch, 40.42...Setting device.

Claims (1)

[Scope of utility model registration request] A radiation source, a detector that receives radiation from the radiation source and electrically converts the incident radiation, and inputs the output of the detector to adjust the electrical zero point when the radiation is shielded. A preamplifier having an operating parameter adjustment means for manually controlling the output of the preamplifier, a level adjustment means for adjusting an output level when measuring zero plate thickness, and a means for adjusting a shift of the output level when measuring intermediate plate thickness. A zero-scale amplifier, a logarithmic amplifier that takes the logarithm of the output of the zero-scale amplifier and outputs a signal proportional to the thickness of the plate to be measured, and inputs the output of the logarithmic amplifier to adjust the level when inserting the maximum plate thickness. A sensitivity amplifier having a gain means for the measurement, a measurement setting device that generates a set plate thickness signal proportional to the plate thickness to be measured, an electrical zero setting signal when inserting a shielding plate, and a zero thickness at a plate thickness of zero at the time of measurement. a setting signal for calibration, a maximum thickness setting signal at the maximum plate thickness at the time of measurement, and an intermediate thickness setting signal corresponding to the intermediate thickness value between zero thickness and the maximum plate thickness at the time of measurement; A shielding plate that can be individually inserted into the radiation flux between the radiation source and the radiation detector, a reference piece with the maximum thickness, a reference piece with an intermediate thickness, and a setting device for calibration that receives a switching command signal. a calibration switch that outputs a setting signal corresponding to this command among the plurality of outputs and the output of the measurement setting device; and a calibration switch that outputs the switching command signal and adjusts the maximum thickness of It consists of a control device for moving the reference plate and the intermediate thickness reference plate into and out of the radiation flux, and a comparison circuit that outputs the deviation between the output of the calibration switch and the output of the sensitivity amplifier,
A radiation thickness gauge characterized in that an adjustment means corresponding to the switching command is adjusted based on the switching command state and the output of the comparison circuit.