APL Applied Physics Laboratory, Faculty of Electronic Engineering, University of Nis, A. Medvedeva 14, P.O. Box 73, 18001 Nis, Serbia A new microcontroller-based RADFET dosimeter reader A new microcontroller-based RADFET dosimeter reader Nikola D. Vasović, Goran S. Ristić Applied Physics Laboratory, Faculty of Electronic Engineering, University of Nis APL A new reader for radiation dose measurements using RADFET (pMOSFET) dosemeters has been developed. The threshold voltage (V ) of the pMOSFETs is measured using a “one-point” method that determines V as the gate voltage for a given drain current. Using V , the absorbed dose, which is directly proportional to the threshold T T T voltage shift, is calculated. The reader is based on a low cost 8-bit PIC 18F4520 microcontroller (MCU), and works independently of a personal computer, uses a touch screen and stores the data in microcontroller memory. Good agreement in threshold voltage values, obtained using a high-quality source-measure unit and the reader, was obtained. In addition, the reader can be used for threshold voltage measurement with other types of MOSFETs, especially in long duration experiments, as well as for the real-time measurements in radiotherapy, either as an autonomous system or integrated in a larger monitoring configuration. ABSTRACT: Radiation Measurements Vol. 47, pp. 272-276 (2012) Fig. 1. Set-up for a measurement of VT in one point (a reader circuit configuration). gate source bulk drain Current Source +V s I D V =V measured T G A EEPROM 256by GLCD TouchPanel Micro Controller 18F4520 MCP3304 13bit A/D SPI TSC272 Lm334 10μA RC S B D G RADFET TouchPanel Controller Power Supply Ds1820 Pt100 +V S V T Fig. 2. Block diagram of the PDOS v1.0 reader. Fig. 4. The photograph of realized PDOS v1.0 reader. +5V 110R 110R 110R Wd3 Wd2 Wd1 PIC18F4520 8 MHz 18 pF Reset +5V 10k 100n TS272 +12V Pt100 Lm334 +12V 1K3 56K +5V MCP3304 pMOS RADFETS Lm334 +12V Ds1820 Ds1820 GLCD + TouchPanel 10k 100k 10k 10k 100k JMP +5V 64R 10K +5V +5V +5V 4K7 4K7 10K 4K7 4K7 10K 4K7 4K7 10K 10K 100n 100n 1K 12VDC 330n +5V 100u + LM7805 Fig. 3. Circuit diagram of PDOS v1.0 reader. A new system, called gasmem v1.0, for the measurements of gas electrical breakdown time delay (t ), with significantly better characteristics than older systems, has been developed and realized. It is based on the PIC 18F4550 microcontroller and could measure the minimal td of about 1.5 μs with the resolution d of 83.33 ns. The relaxation (afterglow) period (τ) could vary from 1 to 232 ms (≈ 50 days). The successive series of td measurements with various τ could be performed, giving very reliable td data that are stored on the personal computer (PC) hard drive via the USB interface. The td and τ values enable the drawing of memory curves (td = f (τ)) and the analysis of memory effects in the gases. The randomness of t values measured by the gasmem system for more τ values was tested using the nonparametric Wald–Wolfowitz test showing the stochastic nature of obtained results. The memory curves obtained by this d system have shown very high reproducibility. In addition, the system has a capability of operating as a stand-alone system (independently of a PC), with the possibility for the implementation of a touch screen for controlling the system and additional memory (e.g. memory card) for data storage. Fig. 1. The block diagram of the gasmem v1.0 system for the td measuring and memory curve recordings. USB Micro Controller 18F4550 HIGH VOLTAGE switching circuit with optocouplers and mosfet driver Power Supply High Voltage Supply 0 V - 1 kV PC Gas tube LCD Micro Controller 16F887 Fig. 2. The modules of the realized gasmem v1.0 system PIC18F4550 Control module Analog switch Switcher trigger Stop signal Voltmeter PIC16F887 LCD 2x16 USB V R Gas tube A LM393N PIC18F4550 15 pF 220 nF 8 MHz 15 pF Vcc 22R 110R 110R 110R Reset Wd1 Wd2 Wd3 HCPL2631 Gejt H +5V Gejt L Stop Voltmetar Stop trimer Vcc +15V +15V +15V Vcc PstopA 1K 1K 470R 1K 100n 390R 22R 6N137 1K2 2K2 18p 10k 100n 220V 50Hz 1A / Fast Prekidac 100n Lm7805 Lm7815 0.2m 330n +15V +5V Lm7805 0.2m 330n +5V 100n 1K FBC Fig. 3. The modules of the realized gasmem v1.0 system IRG4PH40KD Gejt H Gejt L IRG4PH40KD 470n 100u +15V 10R 10R 100n +5V IR2213 0 - 1000 V R3 R4 R12 mA 1M2/3W Gas tube 10K 1K Stop trimer 250mA LM393N +15V +15V PstopA 390R 6N137 FBC 1k 5 X 1M 47K +5V IRG4PH40KD 10 x 10K / 5W Tc429 Pobuda tranzistora +5V +5V Fig. 4. The ASM of the gasmem v1.0 system. Fig. 6. Photographs of the released system. A new, low cost switching system based on PIC 18F4550 microcontroller (MCU), called APL-SM v1.0 system, which enables the successive measuring of both the electrical characteristics in midgap-subthreshold technique (MGT) and charge-pumping currents in charge-pumping technique (CPT) of metal-oxidesemiconductor field effect transistor (MOSFET), has been developed. The APL-SM v1.0 system, instead of expensive switching matrix which price is considerably higher, could be used for the switching from MGT to CPT and vice versa. Using the appropriate program, the system allows the monitoring of MOSFETs during long time periods, helping the performing of long lasting experiments. The good agreement in the electrical characteristics, as well as in the charge-pumping currents, obtained using ultra low current, high speed Keithley switching matrix (SM) and APL-SM system, was obtained. Fig. 2. Block diagram of the experimental set-up for MGT and CPT of four-pin MOSFETs. PC SG SMU1 1 2 3 SMU2 G D S B MGT CPT SG SMU1 1 2 3 SMU2 G D S B GPIB 488 IEEE Fig. 1. Block diagram of the experimental set-up for MGT and CPT of three-pin MOSFETs. PC SG GPIB 488 IEEE SMU1 SMU2 G D S MGT A CPT Sw7 Sw6 Sw5 Sw4 Sw3 Sw2 Sw1 Sw0 PC USB Power Supply Micro Controller 18F4550 Fig. 3. Block diagram of relay controls; Sw0, Sw1, ..., Sw7 are the relays (switchers). Sw6 Sw4 G D S B G B S D SMU2 SG Pt100 SMU1 Sw0 Sw1 Sw2 Sw3 Sw5 Sw7 Sw6 Sw4 G D S B G B S D Pt100 Sw0 Sw1 Sw2 Sw3 Sw5 Sw7 SMU1 SMU2 SG GPIB 488 IEEE PC Bipolar Transistor Driver MGT USB Micro Controller 18F4550 CPT Relay Controls: Sw0 - Sw7 Fig. 4. Switching system maps for four-pin MOSFETs in two modes. Fig. 5. Electrical circuit of realized APL-SM v1.0 system. Sw6 Sw4 Gate Body Source Drain SMU2 SG Pt100 SMU1 Sw0 Sw1 Sw2 Sw3 Sw5 Sw7 12 V 1K 1N4007 12 V 1K 1N4007 12 V 1K 1N4007 12 V 1K 1N4007 12 V 1K 1N4007 12 V 1K 1N4007 12 V 1K 1N4007 12 V 1K 1N4007 PIC18F4550 220 nF 8 MHz 15 pF MCLR RA0 RA1 RA2 RA3 RA4 RA5 RE0 RE1 RE2 VDD GND OSC1 OSC2 RC0 RC1 RC2 RC3 RD0 RD1 Rb7 RB6 RB5 RB4 RB3 RB2 RB1 RB0 VDD GND RD7 RD6 RD5 RD4 RC7 RC6 RC5 RC4 RD3 RD2 5V 220V / 50Hz 2200uF 220 nF LM7812 LM7805 12 V 5V Sw6 Sw4 G D S B G B S D SMU2 SG Pt100 SMU1 Sw0 Sw1 Sw2 Sw3 Sw5 Sw7 Sw6 Sw4 G D S B G B S D Pt100 Sw0 Sw1 Sw2 Sw3 Sw5 Sw7 SMU1 SMU2 SG GPIB 488 IEEE PC Bipolar Transistor Driver MGT USB Micro Controller 18F4550 CPT Relay Controls: Sw0 - Sw7 Fig. 6. Application of APL-SM v1.0 system on three-pin MOSFETs. Fig. 7. Photographs of the released system. ABSTRACT: A system for gas electrical breakdown time delay measurements based on a microcontroller Miomir Todorović, Nikola D. Vasović and Goran S. Ristić Applied Physics Laboratory, Faculty of Electronic Engineering, University of Nis Measurement Science and Technology Vol. 23, 9pp. 015901 (2012) PIC18F887 15 pF 8 MHz 15 pF Vcc 110R 110R Reset Vcc +15V +5V 10k 100n P1: Voltage U 0 P2: Current I 0 Wd1 Wd2 TS272IN 4K7 4K7 4K7 4K7 AinHI1 AinHI2 39R Fig. 5. The VM of the gasmem v1.0 system. ABSTRACT: A switching system based on microcontroller for successive applying of MGT and CPT on MOSFETs Nikola D. Vasović, Goran S. Ristić Applied Physics Laboratory, Faculty of Electronic Engineering, University of Nis Measurement, (2012) DOI: 10.1016/j.measurement.2012.03.011