APLApplied 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 readerNikola 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, wasobtained. 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).

gatesource

bulk

drain

CurrentSource

+Vs

ID

V = Vmeasured

T G

A

EEPROM256by

GLCD

TouchPanel Micro Controller18F4520

MCP330413bit A/D

SP

I

TSC272

Lm33410μA

RC

S

B

D

G

RADFET

TouchPanelController

Power SupplyDs1820Pt100

+VS

VT

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

PIC

18

F4

52

0

8 MHz

18 pF

Reset

+5V

10k 100n

TS272

+12V

Pt100

Lm334

+12V

1K3

56K

+5V

MC

P3

30

4

pMOS RADFETS

Lm334

+12V

Ds1

820

Ds1

820

GLCD+

TouchPanel

10k

100k

10k

10k 100k

JMP

+5V

64R

10K

+5V

+5V

+5V

4K

7

4K

7

10K

4K

7

4K

7

10K

4K

7

4K

7

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 tdmeasuring and memory curve recordings.

US

B

Micro Controller18F4550

HIGH VOLTAGEswitching circuit

with optocouplers and mosfet driver

Power Supply

High VoltageSupply

0 V - 1 kV

PC Gas tube LCD

Micro Controller

16F887

Fig. 2. The modules of the realized gasmem v1.0 system

PIC18F4550

Controlmodule

Analogswitch

Switcher trigger

Stop signal

Voltmeter

PIC16F887

LCD 2x16

USB

V

R

Gas tube

A

LM393N

PIC

18

F4

55

0

15 pF

220 nF

8 MHz

15 pF

Vcc

22R

110R

110R

110RReset

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

2K218p

10k

100n

220V50Hz

1A / Fast

Prekidac

100n

Lm7805Lm7815

0.2m 330n

+15V +5V

Lm7805

0.2m 330n

+5V

100n

1K

FBC

Fig. 3. The modules of the realized gasmem v1.0 system

IRG

4P

H40K

D

Gejt H

Gejt L

IRG

4P

H40K

D

470n

100u

+15V

10R

10R

100n

+5V

IR2213

0 - 1000 V

R3 R4 R12

mA

1M2/3W

Gas tube

10K

1K

Stoptrimer

250mA

LM393N +15V

+15V

PstopA

39

0R

6N137

FBC

1k5 X 1M

47K

+5V

IRG

4P

H40K

D

10 x 10K / 5WTc429

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 SMU2G

D

S

B

MGT

CPT

SG

SMU1

1

2

3 SMU2G

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

SMU2G

D

S

MGT

A

CPT

Sw7Sw6Sw5Sw4Sw3Sw2Sw1Sw0

PCUSB

Power Supply

Micro Controller18F4550

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

Sw7Sw6

Sw4

G

D

S

B

G

B

S

D

Pt100Sw0

Sw1

Sw2

Sw3

Sw5

Sw7

SMU1

SMU2

SG

GPIB 488 IEEE

PCBipolar

TransistorDriver

MGT

USB Micro Controller18F4550

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

Sw1Sw2

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

PIC

18F

4550

220 nF

8 MHz

15 pF

MCLRRA0RA1RA2RA3RA4RA5RE0RE1RE2VDDGNDOSC1OSC2RC0RC1RC2RC3RD0RD1

Rb7RB6RB5RB4RB3RB2RB1RB0VDDGNDRD7RD6RD5RD4RC7RC6RC5RC4RD3RD2

5V

220V / 50Hz2200uF 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

Sw7Sw6

Sw4

G

D

S

B

G

B

S

D

Pt100Sw0

Sw1

Sw2

Sw3

Sw5

Sw7

SMU1

SMU2

SG

GPIB 488 IEEE

PCBipolar

TransistorDriver

MGT

USB Micro Controller18F4550

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 microcontrollerMiomir 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)

PIC

18

F8

87

15 pF

8 MHz

15 pF

Vcc

110R

110R

Reset

Vcc

+15V +5V

10k 100n

P1: Voltage U0P2: Current I0

Wd1Wd2

TS

272IN

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 MOSFETsNikola 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