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When calculating the Radon concentration by the given formula, the concentration value for
the interval with the one count is much too high while all other values show zero. Then, all
intervals have to be averaged to get a usable result. This procedure is nothing else than to
create an integration interval long enough to meet the Detection limit for the applied Radon
concentration. To avoid zero readings, set the integration interval with respect to the lowest
expected concentration level during measurement.
The mean („true") value of the number of decays during an integration interval in case of a
Radon concentration in the surrounding of the detection limit is less than 16 and therefore
the statistical fluctuations have to be derived by the Poisson distribution. The stated
confidence interval gives the probability that the detected number of decays within the
interval is not zero.
Confidence Interval
63,2%
95%
99,75%
Example:
Determination of the detection limit of the Monitor using the „Fast-Mode" and an integration
interval of 60 Minutes. The confidence interval shall be 95% (that means in about 95 from 100
intervals a no zero reading should appear):
Required mean value (number of counts from the table): N = 3. Calculating the detection limit
by the formula:
C = N / (T * S) = 3 cts / (60 min * 8 cts/(min*kBq/m³)) = 0.00625 kBq/m³ = 6.25 Bq/m³ The
detection limit in this case is 6.25 Bq/m³.
Service
We offer a comprehensive repair, maintenance and calibration service for all our products.
Please fill out the form on our homepage
send it to us. We need the device type and serial number as well as a short description of the
error that occurred or the expected service. You will then receive an initial cost estimate from
us as well as information on how to proceed.
The device check and the preparation of the cost estimate for repairs after the warranty has
expired are subject to a fee.
SARAD GmbH 2023
Required Mean Value for N at the Detection Limit
1
3
6
(SARAD -
Manual_RTM1688-2_EN_24-02-2023.docx
Service) BEFORE SENDING A DEVICE and
RTM 1688-2
17
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