Errors in electronic Radon gas monitors ????

http://www.info-optim.ro/abstracts/1791.pdf

Errors in electronic Radon gas monitors due to electromagnetic interferences
L.E. Aciu1**, IEEE Member, P. Ogrutan1, IEEE Member, G. Nicolae1, C. Ursachi**1
1Transilvania University of Brasov, Romania
Abstract
The present paper presents several sets of measurements of electric field at low and high frequency and Radon concentrations
measurement made in a specific location where the values of electric field were higher than the normal ones. The obtained values
were compared with values measured in a reference location.
The Radon concentration measurements were performed both with electronic devices and with the alpha track detectors.
To determine the susceptibility for Radon detectors, tests were carried out for galvanic and radiated disturbances coupling.
Radiated Immunity test were made in a TECM cell in the range 850MHz-900MHz, accordingly to IEC 61000-4-6. Tests
revealed uncertainties of measuring the Radon gas concentrations in the presence of electromagnetic disturbances.
The presence of the electric field and conducted disturbances affects the Radon Gas digital detector.
The test made in TEM cell and in the presence of conducted radiated disturbances according to EU standards confirm this
conclusion.
In the TEM cell, a field average value of 3.05V/m causes a change of 3.74 times of the Radon gas concentrations,
measured in TEM cell, while a field of 280V/m causes a change of only 1.98 times. It can be said that the electric
field in the 850-950MHz affect digital measurement device, but it can not be said that this in the only cause of the
errors that appears. Similarly, the test for burst and conducted disturbance affect Radon detector, introducing
unacceptable errors of 176% and respectively 220%.
a) b) c)
Fig. 1. Radon Gas measurements a)Block diagram for testing in TEM cell, b) Electric field strength values, c) Radon
concentrations measured in the presence and the absence of electric field
Method Average
value
Bq/m
3
Average
value –
reference
location
Limit Electric
Field
HF
Electronic 165 56 148 3.05
Track
detector 44 36 148 0.17
a)
Method Radon
concentration
Electric Field HF Uncert
ainty
Electronic 165 Bq/m
3 3.05 mV/m 375%
Track detector 44 Bq/m
3 3.05 mV/m 0%
b)
Testing Type Average Radon concentration
values in 48 hours
Uncert
ainty
Without perturbation 92.5 Bq/m
3 -
Conducted RF disturbance 203.5 Bq/m
3 220 %
Burst disturbance 162.8 Bq/m
3 176 %
Radiated RF in TEM cell,
without perturbation
21.09 Bq/m
3 -
Radiated RF in TEM cell,
Electric Field 280 mV/m
41.81 Bq/m
3 198 %
Fig.2. Radon concentration comparison Fig.3. Uncertainties in Radon gas concentration measurements
References
[1] J.Viel, ”Testing for Immunity to EMP”, National Technical Systems, July, 2010.
[2] J. Chen, R. Falcomer, B. Walker, “Field Evaluations of Digital Radon Detectors”, Health Physics, vol 93, pp. S184-
S186, November 2007.
[3] P. Giligan, S. Somerville, J.T. Ennis, “GSM cell phones can interfere with ionizing dose monitoring equipment”, British
Hournal of Radiology, vol 73, pp. 994-998, 2000.
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