JPS60187877A - Estimation of true ground level - Google Patents

Abstract

PURPOSE:To stabilize the base line after the shaping of a waveform by feeding back errors obtained from the comparative computation with an arithmetic unit to the unit to estimate the true ground level. CONSTITUTION:An error detection circuit 45 receives the supply of a waveform passing signal 46 from a switching circuit 36 and corrects the ground level in other periods. In the operation, the error detection circuit 45 compares the ground with the potential of on the output side of an arithmetic unit 34 to make the level of a simulation signal 41 outputted from a simulation signal generation circuit 37 with the ground level lL on the linear amplifier side. As a result, the output signal becomes equivalent to the true ground level lL in the zero level thereof and hence, the height thereof corresponds exactly to the peak of a signal 33.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a true ground level for correcting an apparent ground level to a true ground level when, for example, a preamplifier and a linear amplifier are AC coupled. Regarding level estimation method.

1 [Technical Background of the Invention] As shown in FIG. 1, in a radiation measurement device, radiation emitted from a radiation source 11 is detected by a detector 1 such as a germanium detector.
2 is used for detection. This detection output is as weak as μ■. The preamplifier 13 amplifies this to about mV and also shapes the waveform using a built-in RC circuit. A linear amplifier (main amplifier) 14 amplifies this to a voltage level suitable for a measuring device 15 such as a pulse height analyzer, and also shapes the waveform.

Now, when the preamplifier 13 and the linear amplifier 14 are AC-coupled by the capacitor 16 as shown in the figure, the ground level on the linear amplifier 14 side varies depending on the state of the signal output from the preamplifier 13. generally the second
If the preamplifier outputs a pulse signal as shown by the solid line 18 in FIG. Also, the same figure (
When the frequency of the pulse signal increases as shown by the solid line 21 in B), the ground level increases as shown by the broken line 22.

In the radiation measuring device shown in FIG. 1, each time radiation is detected, a pulse signal of 2/4, which decreases exponentially as shown in FIG. ．． Normally, 242... are output one by one. These pulse signals 24. ．． 24
．． . . . depends on the state of the radiation source 11 and is, of course, undetermined. Therefore, in the conventional measuring device of this type, the true ground level cannot be estimated on the linear amplifier side, which causes an error in the measurement result of a subsequent measuring device such as a pulse height analyzer.

[Purpose of the invention]

In view of the above-mentioned circumstances, an object of the present invention is to provide a method capable of estimating the true ground level on the linear amplifier side and stabilizing the baseline after waveform shaping.

[Structure of the invention]

In the present invention, an input signal is detected by the rising or falling edge of its waveform, a signal that simulates the signal is generated after a predetermined period of time has elapsed, and a calculator calculates the difference between these two signals to obtain the predetermined value. In a waveform shaping device that shapes the pulse signal into a pulse signal having a time width equal to time, the difference between the ground level on this device side and the level of the signal output from the arithmetic unit is detected, and This difference between the signals is fed back to the arithmetic unit as an error in the signal level output from the arithmetic unit, and the level is corrected. The ground level after this correction is estimated to be the true ground level of the waveform leveling device i11.

〔Example〕

The present invention will be described in detail below with reference to Examples.

FIG. 4 shows the main parts of a linear amplifier using the true ground level estimation method of this embodiment. A signal 32 having a waveform as shown in FIG. 5a, for example, is input to an input terminal 31 of this linear amplifier. At this time, the preamplifier outputs a signal 33 having a waveform as shown in the figure. That is, the level L of the signal 32 is the ground level of the preamplifier, and a predetermined level difference exists between it and the ground level LL of the linear amplifier.

The signal 32 is input to the signal detection circuit 35 via the arithmetic unit 34. The signal detection circuit 35 detects the rise of the signal 32 and supplies the detection signal to the switch circuit 36. In the switch circuit 36, T
When this period has elapsed, a simulated signal transmission start control signal 39 is sent to the simulated signal generation circuit 37.

The simulated signal generating circuit 37 includes, for example, an exponential function generating circuit composed of a capacitor and a resistor, and charges are stored in the capacitor in response to the signal 32. Then, from the time when the simulated signal transmission start control signal 39 is manually input, a simulated signal 41 (FIG. 5C) that decreases exponentially is generated. The waveform of the signal 32 input to the input terminal 31 is determined in advance by the preamplifier. Therefore, when a preamplifier that outputs a pulse signal that decreases exponentially is used, a similar waveform as described above will be output as the simulated signal 41. Further, when a waveform in which the DC level changes stepwise as shown in FIG. 6 is manually generated, the simulated signal 41 also has a stepwise waveform simulating this.

In the case of the simulated signal 41 shown in the figure, the signal level decreases (or increases) by the offset △■ on the linear amplifier side.
The voltage is the apparent ground level of the linear amplifier.
It becomes L'.

Now, the arithmetic unit 34 uses a simulated signal 41 outputted from the simulated signal generation circuit 37 and a signal 32 manually inputted from the input terminal 31.
Take the difference between The resulting output signal 42 is supplied to an output terminal 43, from which it is sent to a subsequent circuit section.

By the way, FIG. 5d shows the waveform of the output signal 42' on the assumption that no ground level correction is performed. As can be understood from this figure, the output signal 42 falls at once by the difference in response to the rise of the waveform of the simulated signal 41 (C in the figure), but even after that, it remains at the apparent ground level IL' of the linear amplifier. decreases exponentially. Therefore, with such an output signal 42', it is not possible to obtain a pulse signal with a wave height that accurately corresponds to the wave height of the signal 33 output from the preamplifier side.

Therefore, in this embodiment, the error detection circuit 45 is used to correct the ground level. The error detection circuit 45 receives a waveform passing signal 46 (FIG. 5e) from the switch circuit 36, and corrects the ground level during other periods. Here, the waveform passing signal 46 is a pulse signal that is generated for a time T from the rising edge of the signal 32. That is, the error detection circuit 45 compares the potential of the ground and the output side of the arithmetic unit 34, and matches the level of the simulated signal 41 outputted from the simulated signal generation circuit 37 with the ground level IIL of the linear amplifier side. As a result, the zero level of the output signal becomes the true ground level 1L, as shown in Figure 5f.
Therefore, the wave height corresponds exactly to the wave height of the signal 33.

〔Effect of the invention〕

As described above, according to the present invention, the error obtained by the comparison calculation of the arithmetic unit is fed back to the arithmetic unit to estimate the true ground level.

Therefore, as shown in the embodiment, it is possible to effectively deal with not only ground level fluctuations due to AC coupling, but also offsets on the preamplifier and linear amplifier side due to causes such as temperature, improving the accuracy of wave height analysis, etc. I can do it.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the general configuration of a radiation measurement device, Figures 2 (Δ) and (B) are waveform diagrams showing the relationship between the duty of the pulse signal and the ground level, and Figure 3 is a waveform diagram showing the relationship between the duty of the pulse signal and the ground level. The figure is a waveform diagram showing an example of a signal output from a preamplifier, Figure 4 is a block diagram showing the main parts of a linear amplifier to which the true ground level estimation method is applied in an embodiment of the present invention, and Figure 5 is a waveform diagram showing an example of a signal output from a preamplifier. Various waveform diagrams for explaining circuit operations in the embodiment, and FIG. 6 are waveform diagrams showing other examples of input signals. 32... Input signals, 34... ... Arithmetic unit, 41 ... Simulated signal, 42 ... Output signal, 45 ... Error detection circuit, flL ... Ground level on the linear amplifier side. Output Applicant: Representative of Japan Atomic Energy Corporation, Patent Attorney Umeo Yamauchi

Claims (1)

[Claims] 1. Detect a human input signal by the rising or falling edge of its waveform, generate a signal that simulates the signal after a predetermined period of time has elapsed, and use a calculator to calculate the difference between these two signals to determine the predetermined time. In a waveform shaping device that shapes a pulse signal into a pulse signal having an equal time width, the difference between the ground level on this device side and the level of the signal output from the arithmetic unit is detected, and A true ground level estimation method in which this difference is returned to the computing unit as an error in the signal level output from the computing unit, the level is corrected, and the signal level of this part after the correction is estimated as the true ground level. .