Magtrol LMU 212, Руководство пользователя

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Magtrol Load Monitoring Units LMU 212 & 217
Chapter 4 – Applications
4.3.2 “ok”
philosophy
When using simultaneously several load monitoring units, the "OK" inputs and outputs allow the user
to cascade the operational checks of the different units and obtain overall control of the measuring
chain.
If the output signal "OK" (OK
O/P
) of a load monitor indicates a fault (low impedance), either the
transmission between the transducer and the load monitoring unit is interrupted or short-circuited,
or the load monitoring unit is defective.
If several load monitoring units are cascaded, the unit causing potentionally a problem sends this
information to all following monitoring units. So, all effects described in the previous chapter
4.3.1
will be displayed on the LMU outputs and on all downstream load monitoring units connected to
the measuring chain. In case of a defect inspect the output voltages U
O/P
[terminal (15)– grounding
(7), voltage >10 VDC] or the current output I
O/P
[terminal (10)– grounding (7), current >20 mADC].
Another method of localising a default is to interrupt the line OK
I/P
− OK
O/P
between the load
monitoring units and then short-circuit terminal (8) and (11) of the suspected LMU(s). If the voltage
measured between terminal (8) and the ground (7) is less than 1 VDC, something must be wrong
with the LMU. If the voltage is around 24 VDC, the LMU is ok. Remove the short circuit after
having carried out the measurements.
4.5 perManent supply CheCk
The load monitoring unit LMU is fitted with a device, which permanently checks the internally
generated voltage supplies. Any drop of one of these voltages causing a problem on the LMU will
force the LMU to switch to error mode with the following effects:
• The relays REL1 and REL2 will be de-energised.
• The LED shown on
figure 4–5 will go off.
As far as possible (the basic supply units must still remain operational) the voltage and current
outputs (U
O/P
respectively I
I/P
) indicate the problem:
• The OK
O/P
will go on error mode (low impedance).
• Current output I
O/P
> 20 mA.
• Voltage output U
O/P
> 10 V DC.
"OK supply" LED
Fig. 4–5 Permanent supply check LED