Endress+Hauser gammapilot FTG 671, Руководство по эксплуатации

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4.5 Limit switches
Default settings On completion of the calibration, the (max.) countrate registered with the barrier free is
assigned the normalised countrate 0 and the (min.) countrate registered with the barrier
covered, the normalised countrate 100. The Gammapilot FTG 671 automatically sets the
following switch points.
•
Relay 1 is set to operate in minimum fail-safe mode with switch-off point at 38
and switch-on point at 72 normalised countrate (10/90 for DG 17/27).
•
Relay 2 is set to operate in minimum fail-safe mode with switch-off point at 72
and switch-on point at 38 normalised countrate (90/10 for DG 17/27).
•
On fault condition, both limit relays de-energise.
Table 4.2 indicates the Gammapilot relay responses. If other limits are required or the
relays are to be operated in acknowledgement mode, the settings can be changed as
described in Chapter 5, p. 35.
Switch point monitor Once the relays are set, the Gammapilot monitors the switchpoints as follows:
•
Decay compensation
This function ensures that the maximum and minimum countrate are corrected
for the natural decay in the activity of the radioactive source. It is run once
every twenty four hours.
•
Minimum countrate check
The measured countrate is checked continuously against the corrected mini-
mum countrate. If it is smaller, Alarm E 201 is set, the alarm relay trips and the
alarm LED lights. In default mode, the limit relays de-energise.
•
Maximum countrate check
The measured countrate is checked continuously against the corrected maxi-
mum countrate. If it is greater, Alarm E 202 is set, the alarm relay trips and the
alarm LED lights. This alarm usually indicates the presence of external gam-
ma radiation. In default mode, the limit relays de-energise.
•
Plausibility test
The limits are checked with respect to their plausibility every four minutes. If
the test is failed, Warnings E 631
…
635 may be set and the alarm LED flashes.
Minimum fail-safe mode Maximum fail-safe mode
Level Relay status LED Level Relay status LED
Drops below
switch-off point De-energised
Green Red
off on
Rises above
switch-off point De-energised
Green Red
off on
Rises above
switch-on point Energised
Green Red
on off
Drops below
switch-on point Energised
Green Red
on off
Table 4.8:
Truth table for minimum and
maximum fail-safe mode
z18 d18 b20
z22 d22 b24
z18 d18 b20
z22 d22 b24
z18 d18 b20
z22 d22 b24
z18 d18 b20
z22 d22 b24
Gammapilot FTG 671 Chapter 4: Calibration and Operation
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