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Mobile pulse electrometer for measuring small ionization chamber currents in continuous and pulsed radiation fields


Based on the long‑term experience and developments of Department 6.3 with regard to measuring very small currents of ionization chamber (in the range of a few 10‑15 amperes), a compact mobile measuring instrument was developed within the scope of a technical project. To this end, an innovative principle for measuring ionization currents and charges simultaneously was enhanced. In addition, modern communication technology (WiFi) was integrated into this compact measuring instrument that will for the first time allow the mobile measurement of dose and dose rate in continuous as well as in pulsed radiation fields.

Air ionization chambers are used as secondary standards in radiation protection dosimetry for photon radiation because their response is largely independent of the incident photon energy. These chambers therefore enable reliable measurements even in almost unknown radiation fields legal radiation protection applications. In certain cases or within the scope of project activities, PTB also performs measurements at external facilities where the radiation fields are often unknown. For such tasks, it is important that the equipment used is easily transportable and mobile.

A novel mobile pulse electrometer has been developed for this type of use. Thanks to its multiple charge measuring ranges that are simultaneously active, it is a valuable and innovative development, in particular for measuring unknown pulsed radiation fields.

Pulsed radiation requires the measurement of an unknown amount of pulsed dose and therefore of an unknown amount of charge. Here, the simultaneous measurement over several parallel charge integrator ranges is a great advantage. Also, the dose rate of continuous radiation is simultaneously determined by measuring the current via a shunt resistance. This lifts the limitations of previous measurement techniques and allows immediate, reliable measurement in an entirely unknown radiation field.

A power‑saving microprocessor (Silicon Labs Giant Gecko ARM‑M4) was selected to acquire the analog signals of the electronic components described above. Additional modules allowing the chamber BIAS voltage to be generated and the temperature and air pressure to be measured were also integrated into the firmware. The data connection between the measuring instrument and the terminal was realized via an HTML server on an ESP32 microprocessor which is integrated into the measuring instrument. Thus, any browser‑compatible device such as a PC, a tablet computer or a cellphone can be used as a terminal.

This cooperation project with the Technikakademie der Stadt Braunschweig was aimed at implementing the enhancing measures described above.

mobile pulse electrometer

Figure 1: Mobile pulse electrometer in operation, connected to a browser‑compatible terminal (laptop) to display the measurement results and to control the mobile pulse electrometer. The secondary standard connected is the HS01 ionization chamber, which is optimized to measure the ambient dose equivalent H*(10).


Opens local program for sending emailJ. Roth, Department 6.3, Working Group 6.35

Opens local program for sending emailH. Zutz, Department 6.3, Working Group 6.31

Opens local program for sending emailO. Hupe, Department 6.3