Gammapilot M
12 Endress+Hauser
Suppression of interference radiation using the Gamma-Modulator FHG65
The Gammapilot M can suppress interference radiation when used in conjunction with the Gamma-modulator
FHG65. The useful radiation is switched on and off periodically by the modulator using a fixed frequency.
The Gammapilot M can filter this alternating portion out of the total radiation as a measured value. This does
not entail any interruption to measurement or point level detection as in the case of basic gammagraphy
detection.
The following diagram shows, for example, a comparison between pulse rates with and without the
suppression of interference radiation.
SD230en08
Measuring signal of Gammapilot M in the event of interference radiation, for example
This function suppresses all sources of interference radiation, regardless of the source of useful radiation in use,
up to a local dose rate of approx. 50 μSv/h at the Gammapilot M (depending on detector length and the source
of interference involved).
Higher local dose rates can lead to a reduction in the detected pulse rate due to the statistical superposition of
pulses. This means that, for example, non-destructive material testing using gamma sources in the direct
vicinity of the Gammapilot M may lead to an overflow signal. Therefore, in these cases too, the Gammapilot M
is guaranteed to behave in a fail-safe manner.
!
Note!
• The failure of the modulator (e.g. due to power failure) in this mode of operation, results in the Gammapilot
M having a higher output current (max. 20.5 mA) and is therefore fail-safe.
• In this operating mode of the Gammapilot M, modulator failure during the calibration of the measuring point
may cause the error message A692 "Gammagraphy detected" in the subsequent measuring mode.
35000
30000
25000
20000
15000
10000
0
5000
0
90 180 270 360 450
Time [s]
Behavior in the event of interference radiation
Pulse rate
[cps]
without suppression of interference radiation
with suppression of interference radiation
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