The Environmental Radon Daughter Monitor (ERDM) is a microprocessor-based radiation monitoring system developed by RDS for the monitoring of the potential alpha energy concentration (PAEC) of radon daughters in outdoor and indoor environments.
The ERDM is powered by an external battery or a 240 VAC-to-DC power adaptor with output between 7.2 V and 14.2 V. It can continuously monitor and log data into the microcontroller memory for about 3 months at a 10-minute logging interval. With a 60-minute logging interval, the system can continuously gather data for about 1.5 years.
Air with radon daughters is continuously sampled by the constant 0.3 L/min flow-rate air sampler. Radon decay products are filtered by a glass-fibre filter and the alpha particles emitted by the radon daughters on the filter are detected by a ZnS(Ag) scintillation foil coupled with a photomultiplier tube. The Lowest Limit of Detection (LLD) of the ERDM is approximately 0.04 µJ/m³.
The ERDM can also be used for sampling long-lived alpha activity of airborne dust. After completion of the radon-daughter monitoring, the filter with long-lived dust is removed from the ERDM and alpha-counted after a lapse period of no fewer than 5 days.
Logged data can be downloaded into a MS Windows Hyperterminal as a text file that can be opened in MS Excel.
Gallery
