A Geiger-Müller counter signal acquisition circuit

Abstract

The present invention discloses a Geiger-Müller counter signal acquisition circuit. This circuit incorporates a delayed discharge circuit at the output stage, accelerating the discharge of the GM tube cathode charge and shortening the GM tube circuit's dead time. Specifically, the circuit comprises a GM tube sampling circuit and a delayed discharge circuit. The GM tube sampling circuit is connected to the cathode of GM tube G1. The output stage of the GM tube sampling circuit is connected to the delayed discharge circuit and then to a counter. This accelerates the discharge of the GM tube cathode charge and shortens the GM tube circuit's dead time. The signal acquisition circuit proposed in this invention features a fixed output signal width determined by charging resistor R5 and charging capacitor C1, with dead time matching for different GM tubes. When the GM tube is overloaded, the circuit maintains continuous charging and discharging, outputting a fixed-frequency signal, preventing a drop in count rate due to overload.

Description

Technical Field

[0001] The invention belongs to the technical field of counter signal acquisition circuits, and in particular relates to a Geiger-Mueller counter signal acquisition circuit. Background Art

[0002] At present, radioactive materials and radiation devices are widely used in various fields such as production, scientific research, medical treatment, biology, and laboratories. As radioactive detection instruments, especially x and gamma personal dose (rate) meters and x and gamma inspection meters, they are necessary measuring equipment for radioactive workers and environmental monitoring of radiation environment sites.

[0003] The Geiger-Müller counter (GM tube) is the most widely used detector device in radioactivity measurement instruments. It features compact size, reliable performance, simple data acquisition circuitry, and high cost-effectiveness. However, GM tubes have a long dead time, making them prone to accumulation and blockage. This degrades the linearity of the dose rate measured by the GM tube, and can even cause a drop in the indicated value when the dose rate exceeds a certain level.

[0004] Most of the existing GM tube signal acquisition circuits use Figure 1 The circuit shown uses C1 to capture the AC signal when the GM tube is conducting. This circuit cannot effectively distinguish between partially overlapping pulses, resulting in a longer dead time in the system and a drop in counts when the GM tube is overloaded. Summary of the Invention

[0005] The purpose of the present invention is to solve the deficiencies of the prior art and provide a Geiger-Müller counter signal acquisition circuit, which specifically adopts the following technical solutions:

[0006] A Geiger-Müller counter signal acquisition circuit includes a GM tube sampling circuit and a time-delay discharge circuit, wherein the GM tube sampling circuit is connected to the cathode of the GM tube G1, and the output stage of the GM tube sampling circuit is connected to the time-delay discharge circuit and then connected to the counter, which can accelerate the discharge of the GM tube cathode charge and shorten the dead time of the GM tube circuit.

[0007] Furthermore, the GM tube G1 is connected to an anode current limiting resistor R1.

[0008] Furthermore, the GM tube sampling circuit includes a sampling resistor R2, a first switching tube Q1 and a pull-up resistor R3. The cathode of the GM tube G1 is connected to the base of the first switching tube Q1 through the sampling resistor R2; the collector of the first switching tube Q1 is respectively connected to the pull-up resistor R3, the counter Ct and the delayed discharge circuit, and the emitter of the first switching tube Q1 is grounded.

[0009] Furthermore, the delayed discharge circuit includes a current-limiting resistor R4, a second switch tube Q2, a charging resistor R5, a charging capacitor C1, a capacitor discharge resistor R6, a gate protection resistor R7, a third switch tube Q3, and a fourth switch tube Q4. The current-limiting resistor R4 is connected between the collector of the first switch tube Q1 and the base of the second switch tube Q2. The emitter of the second switch tube Q2 is connected to a power supply. The collector of the second switch tube Q2 charges the charging capacitor C1 through the charging resistor R5. The charging capacitor C1 is connected to the base of the fourth switch tube Q4. The other end of the charging capacitor C1 is grounded. The gate of the third switch tube Q3 is connected to the collector of the first switch tube Q1 through the gate protection resistor R7. The drain of the third switch tube Q3 is connected to the charging capacitor through the capacitor discharge resistor. The source of the third switch tube Q3 is grounded. The collector of the fourth switch tube Q4 is connected to the cathode of the GM tube G1. The emitter of the fourth switch tube Q4 is grounded. When gamma rays enter GM tube G1, the gas inside GM tube G1 is ionized, causing an avalanche discharge. Charge flows into the base of first switch tube Q1 through GM tube sampling resistor R2, turning on first switch tube Q1 and dropping its collector to zero potential. Second switch tube Q2 turns on, and third switch tube Q3 turns off. Second switch tube Q2 then charges charging capacitor C1 through charging resistor R5. When the voltage on charging capacitor C1 reaches the turn-on voltage of fourth switch tube Q4, fourth switch tube Q4 turns on, and the charge at the cathode of GM tube G1 is rapidly discharged through fourth switch tube Q4. The base voltage of first switch tube Q1 drops to zero potential, turning off first switch tube Q1 and returning its collector to a high level. Second switch tube Q2 turns off, stopping charging capacitor C1. Third switch tube Q3 turns on, and fourth switch tube Q4 turns off. Charging capacitor C1 discharges to zero potential through capacitor discharge resistor R6 from third switch tube Q3, waiting for the next gamma ray to enter GM tube G1 and trigger an avalanche discharge.

[0010] The beneficial effects of the present invention are:

[0011] The signal acquisition circuit proposed in the present invention adds a delayed discharge circuit at the output stage, which can accelerate the discharge of the GM tube cathode charge and shorten the GM tube circuit dead time. The tube dead time is only one-third of that of the conventional circuit, and the instrument measurement upper limit can be increased by more than 3 times.

[0012] The output signal width of the present invention is determined by the charging resistor R5 and the charging capacitor C1. Since the dead time of different types of GM tubes is different, the circuit sets different times by adjusting R5 and C1 to achieve dead time matching of the GM tubes.

[0013] When the GM tube is overloaded, the charging and discharging process of the present invention will continue to work and output a fixed frequency signal, and the counting rate will not drop due to overload.

[0014] The method of the present invention is simple and can be well mastered by designers and applied to actual designs. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The figure shows the conventional GM tube signal acquisition circuit;

[0016] Figure 2 Shown is a circuit diagram of embodiment 1 of the present invention;

[0017] Reference numerals: GM tube G1, anode current limiting resistor R1, sampling resistor R2, pull-up resistor R3, current limiting resistor R4, charging resistor R5, capacitor discharge resistor R6, gate protection resistor R7, charging capacitor C1, first switch tube Q1, second switch tube Q2, third switch tube Q3, fourth switch tube Q4, counter Ct. DETAILED DESCRIPTION

[0018] The following will be combined with the embodiments and drawings to clearly and completely describe the concept, specific structure and technical effects of the present invention so as to fully understand the purpose, scheme and effect of the present invention. It should be noted that the embodiments and features in the embodiments of this application can be combined with each other unless there is a conflict. The same reference numerals used throughout the drawings indicate the same or similar parts.

[0019] Example 1

[0020] A Geiger-Müller counter signal acquisition circuit is implemented using discrete circuits. That is, discrete passive components are fabricated on a circuit board to implement the GM counter signal acquisition circuit design. The signal output width is fixed and adjustable, and a GM tube dead time matching design can be achieved. The circuit includes a GM tube sampling circuit and a delayed discharge circuit. The GM tube sampling circuit is connected to the cathode of the GM tube G1. The output stage of the GM tube sampling circuit is connected to the delayed discharge circuit and then connected to the counter. This can accelerate the discharge of the GM tube cathode charge and shorten the GM tube circuit dead time.

[0021] Specifically, the anode of the GM transistor G1 is connected to an anode current-limiting resistor R1. The GM transistor sampling circuit includes a sampling resistor R2, a first switching transistor Q1, and a pull-up resistor R3. The cathode of the GM transistor G1 is connected to the base of the first switching transistor Q1 via the sampling resistor R2. The collector of the first switching transistor Q1 is connected to the pull-up resistor R3, a counter Ct, and a delayed discharge circuit. The emitter of the first switching transistor Q1 is grounded, and the other end of the pull-up resistor R3 is connected to a power supply.

[0022] Specifically, the delayed discharge circuit includes a current-limiting resistor R4, a second switching tube Q2, a charging resistor R5, a charging capacitor C1, a capacitor discharge resistor R6, a gate protection resistor R7, a third switching tube Q3, and a fourth switching tube Q4. The current-limiting resistor R4 is connected between the collector of the first switching tube Q1 and the base of the second switching tube Q2. The emitter of the second switching tube Q2 is connected to a power supply. The collector of the second switching tube Q2 charges the charging capacitor C1 through the charging resistor R5. The charging capacitor C1 is connected to the base of the fourth switching tube Q4. The other end of the charging capacitor C1 is grounded. The gate of the third switching tube Q3 is connected to the collector of the first switching tube Q1 through the gate protection resistor R7. The drain of the third switching tube Q3 is connected to the charging capacitor through the capacitor discharge resistor. The source of the third switching tube Q3 is grounded. The collector of the fourth switching tube Q4 is connected to the cathode of the GM tube G1. The emitter of the fourth switching tube Q4 is grounded. When gamma rays enter GM tube G1, the gas inside GM tube G1 is ionized, causing an avalanche discharge. Charge flows into the base of first switch tube Q1 through GM tube sampling resistor R2, turning on first switch tube Q1 and dropping its collector to zero potential. Second switch tube Q2 turns on, and third switch tube Q3 turns off. Second switch tube Q2 then charges charging capacitor C1 through charging resistor R5. When the voltage on charging capacitor C1 reaches the turn-on voltage of fourth switch tube Q4, fourth switch tube Q4 turns on, and the charge at the cathode of GM tube G1 is rapidly discharged through fourth switch tube Q4. The base voltage of first switch tube Q1 drops to zero potential, turning off first switch tube Q1 and returning its collector to a high level. Second switch tube Q2 turns off, stopping charging capacitor C1. Third switch tube Q3 turns on, and fourth switch tube Q4 turns off. Charging capacitor C1 discharges to zero potential through capacitor discharge resistor R6 from third switch tube Q3, waiting for the next gamma ray to enter GM tube G1 and trigger an avalanche discharge. When the GM tube G1 is overloaded, a continuous current will flow from the anode A to the cathode K of the GM tube G1, the fourth switch tube Q4 will be intermittently turned on and off, and the collector of the first switch tube Q1 will output a continuous square wave pulse signal.

[0023] This embodiment uses a J302GM counter tube. Specific test data are shown in Figure 1:

[0024]

[0025] As shown in Table 1 above, for the same model GM tube, the overall dead time of the patented circuit is only one-third of that of the conventional circuit, and the upper limit of the instrument measurement can be increased by more than 3 times.

[0026] The above description is merely a preferred embodiment of the present invention. The present invention is not limited to the above-described embodiments. As long as the technical effects of the present invention are achieved by the same means, they shall fall within the scope of protection of the present invention. Within the scope of protection of the present invention, various modifications and variations of the technical solutions and / or implementation methods may be made.

Claims

1. A Geiger-Müller counter signal acquisition circuit, characterized in that: The signal acquisition circuit comprises: GM tube (G1); A GM tube sampling circuit is connected to the cathode of the GM tube (G1), comprising a sampling resistor (R2), a first switch tube (Q1) and a pull-up resistor (R3); the cathode of the GM tube (G1) is connected to the base of the first switch tube (Q1) via the sampling resistor (R2); the collector of the first switch tube (Q1) is respectively connected to the pull-up resistor (R3), a counter (Ct) and a time-delay discharge circuit, and the emitter of the first switch tube (Q1) is grounded; A time-delayed discharge circuit, wherein the output stage of the GM tube sampling circuit is connected to the time-delayed discharge circuit and then connected to a counter (Ct), wherein the time-delayed discharge circuit comprises a current-limiting resistor (R4), a second switch tube (Q2), a charging resistor (R5), a charging capacitor (C1), a capacitor discharge resistor (R6), a gate protection resistor (R7), a third switch tube (Q3) and a fourth switch tube (Q4); a current-limiting resistor (R4) is connected between the collector of the first switch tube (Q1) and the base of the second switch tube (Q2), the emitter of the second switch tube (Q2) is connected to a power supply, and the collector of the second switch tube (Q2) is connected to a power supply. A charging resistor (R5) charges the charging capacitor (C1); a gate protection resistor (R7) is connected between the gate of the third switch tube (Q3) and the collector of the first switch tube (Q1); a capacitor discharge resistor (R6) is connected between the drain of the third switch tube (Q3) and the charging capacitor (C1); the source of the third switch tube (Q3) is grounded; the charging capacitor (C1) is connected to the base of the fourth switch tube (Q4); the other end of the charging capacitor (C1) is grounded; the collector of the fourth switch tube (Q4) is connected to the cathode of the GM tube (G1); and the emitter of the fourth switch tube (Q4) is grounded.

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