KROHNE IFC 210 E-EEx EN - Manual (Page 64)

Sect. 6.6 Part C Special applications, functional checks, service, and order numbers
IFC 210 E 05/2002
64
6.6 Stable signal outputs when measuring tube empty
Important, please note!
•
Observe the directions and regulations and the electrical data specified in the
EC type test certificate.
•
In addition to the regulations for heavy-current installations (VDE 0100),
pay particular attention to the requirements specified in EN 60079-14 “Electrical
equipment in hazardous areas”.
•
Assembly, installation, commissioning and maintenance work may only be carried
out by ”personnel trained in explosion protection” !
Output signals can be stabilized to values as for “zero” flow to prevent random output signals
when the measuring tube is empty.
- Display: 0
- Current output: 0 or 4 mA, see setting in Fct. 1.05
- Pulse output:
no pulses (= 0 Hz), see setting in Fct. 1.06
Precondition: - electrical conductivity of product:
≥
200 µS/cm,
≥
500 µS/cm for meter sizes DN 2.5 – 15 and
1
/
10
” –
1
/
2
”
- Signal cable length
≤
10m and vibration free with signal converter
- Homogeneous liquid products, free of solids and gasses an do not tend to
electrical or catalytic reactions.
LA / S3 Empty Tube indication LA / S2 Empty Tube stabilization
steady display at “0“ flow LA / S4 electrode cleaning
and Empty Tube stabilization
LA / S3 actively detects an empty
measuring tube and switches
outputs and display to “0“ flow.
When the measuring tube is
empty, resistance between the
electrodes becomes very high.
A low current flows through the
-15 V at the one electrode (the
other is connected to 0 V, chassis)
via the high-resistance resistor and
overdrives the instrumentation
amplifier and then the A/D
converter. This overdriving is
evaluated. LA / S2 should be used when
problems are encountered with LA /
S3, e.g. due to electrolysis effects.
Display is then particularly
unsteady.
At “0“ flow, the electrodes are
connected to 0 V (chassis) via high-
resistance resistors. LA / S4 prevents any deposits of
high-resistance layers on the
electrodes (e.g. fat from very
creamy milk) and effects
stabilization similar to the LA / S2.
For this purpose, the electrodes
are connected to –15 V via high-
resistance resistors.
To join the “semicircles“ of the two
soldering points S1 and S4,
see under ”Point 5“. To join the “semicircles“ of the two
soldering points S1 and S2,
see under ”Point 5“. To join the “semicircles“ of the two
soldering points S3 and S4,
see under ”Point 5“.
Under Fct. 3.06 Applications, set
“yes“ for empty pipe. Possibly reset low-flow cutoff
(SMU), see under Point 8 Possibly reset low-flow cutoff
(SMU), see under Point 8
- 15 V 0 V