KROHNE VFM 5090 EN - Manual (Page 50)

7. Functional checks
This section describes some functional checks which
can be performed without using any special
equipment. It must be noted that these checks are
very preliminary and do not check the total
functionality of the primary head or the signal
converter.
7.1 Primary head functional checks
7.1.1 Vortex sensor
To perform preliminary testing of the vortex piezo
sensor, the signal cable of the piezo sensor should be
disconnected from the signal converter electronics.
To do this : always switch-OFF power source
before commencing work!
1. Use the special wrench to remove the cover
from the electronic compartment. Ensure that
screw threads of electronic compartment cover
are well greased at all times!
A
Power
supply
board
D
D
A
CPU board
Z
Y
X
Preamplifier
board
Flat cable
to Display
board
2. Remove screws A and fold display board to side.
3. Remove the piezo cable from the preamplifier
board at location Z by its connector (and not by
pulling cable itself!)
4. Do the following tests.
Capacitance between centre pin and each outer pin.
ANSI
DN 3/8” S to 1”
10S to 25 1.5”, 2”
40, 50 3” & above
80 & above
C(nF) 0.8 to 1.5 2.0 to 3.4 2.7 to 4.5
Resistance between centre pin and each outer pin >
200 M ohm. Also resistance between each sensor
wire pin and earth should be > 200 M ohm.
Part C Function Checks and Trouble Shooting hints
5. Re-assemble converter in the reverse order
7.1.2 Temperature Sensor
PT-1000 temperature sensor can be checked by
measuring its resistance.
Always switch-OFF power source before
commencing work!
Follow the steps 1, 2 same as in the above Section.
7.1.1
3. Remove the temperature sensor cable at location
Y of the preamplifier board. Pull cable by its
end connector and not by cable itself!
4. Resistance between the 2 pins should be within
1K [0
0 C] - 1.193k [50 0 C] depending on the
ambient temperature. For other temperatures
resistance values as per DIN43760.
5. Re-assemble converter in the reverse order.
7.2 Signal converter functional checks.
7.2.1 Self
diagnostics
On power-ON VFC 090 itself carries out diagnostic
checks wherein the instrument checks its functional
elements as far as possible. Diagnostic failure result
in fatal errors and are indication of a hardware fault
within electronics. Usually it is necessary to replace
electronics in such cases.
Meanings of diagnostic error messages are given
below for information purpose.
Error message Meaning
INTL.ERR20 RAM (read/write memory) failed
INTL.ERR21 EPROM (program memory) failure
INTL.ERR22 GA (Gate Array) failure
INTL.ERR23 Interrupt function failure
INTL.ERR24 LCD (display) controller failure
INTL.ERR25 Timer channel #0 failure
INTL.ERR26 Timer channel #1 failure
INTL.ERR27 Timer channel #2 failure
INTL.ERR28 A/D converter #1 failure
INTL.ERR29 A/D converter #2 failure
INTL.ERR30 NOVRAM(nonvolatile mem.)failure
INTL.ERR31 EEPROM failure
INTL.ERR32 UART (Communication controller)
failure
INTL.ERR33 KEYS (3 Keys on display board)
problem
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