KROHNE DWM 1000-2000 EN - Manual (Page 10)

10
Trouble Shooting
Below is a list of possible problems, and the checks required for their resolution. In all cases ensure that the installa-
tion instructions have been followed e.g. supply voltage, relay compatibility (DWM1000 only), earthing (<10 Ohms),
straight line flow distances, and flow in pipe is full.
DWM 1000
Fault: The relay does not switch according to reference velocity.
Checks Action
When the selector is inverted, does the relay If no, measure the consumption of the unit whilst the LED is
switch? illuminated. If i<5.5mA for DC (12 mA for AC), insert a resistor in
parallel with the relay coils of ratings 1, 3 or 10kOhms (5W)
corresponding to voltages 48, 110, and 230V respectively.
Advance the reference velocity from 0 m/s If no, and the LED changed state, replace the electronics unit.
through to 9m/s - does the relay switch? If yes, note the reference velocity value, and check this against
the real velocity.
Fault: The relay switches randomly.
Checks Action
Liquid heavily charged with particles? Flow Increase the time constant to 10s. If results are the same,
speed close to 0.1m/s? Straight line flow increase the reference velocity. If the results remain the
distances too short? Air bubbles in liquid same, insert a resistor in parallel with the relay coils of ratings 1,
(at high temperatures)? 3 or 10kOhms (5W) corresponding to voltages 48, 110, and
230V respectively.
DWM 2000
Fault: The output current is fixed at 0mA.
Checks Action
Output signal correctly powered? Refer to Technical Data specifications.
Polarity correct on supply connections? Refer to wiring diagrams.
Liquid inside the probe body? Contact KROHNE Service Department.
Fault: The pipe flow is higher than 0.1m/s and the output current remains at 4mA (+/- 0.02mA).
Checks Action
Orientation of the electronic unit correct? Loosen the fixing screws, and align the arrow with the pipe flow
Fault: The output current is fixed at below 3mA.
Checks Action
Power supply stable? (nominally +/-1%) Change power supply.
Current at 2.0mA? Reset the Full Scale switches to between 1 and 8m/s.
Current at 2.4mA? Zero setting too large - reset the zero with the pipe full and v=0
m/s.
For all other alarm output readings, contact KROHNE.
Fault: There is no flow in the pipe, and the output current is instable (4mA +/-1mA).
Checks Action
Is the output current stable when tested If no, trace and eliminate the interference source.
by a multi-meter?
Is the earth <10 Ohms?
Establish a correct earthing point.
Fault: The output current is above 4mA, but the reading is incorrect.
Checks Action
Reading above 24mA? Ensure conformity to power supply specifications.
Fluctuations, but average reading correct? Increase the time constant value using the HHC2000 console.
Installation correct? Verifiy mounting specifications (probe penetration in pipe, right-
angles, orientation of electronic unit).
Pipe not full? Ensure that the pipe is full during flow conditions.
Speed/flow calculations correct? Check the internal diameter of the pipe and reset the Full Scale.
Is the output current correctly calibrated? Test the output current with the HHC2000 console.