SMAR LD303, Operation And Maintenance Instruction Manual, Page: 69 / 110

Section 4
4.1
MAINTENANCE PROCEDURES
General
NOTE
Equipments installed in hazardous atmospheres must be inspected in compliance with the
IEC60079-17 standard.
SMAR Series 303
devices are extensively tested and inspected before delivery to the end user.
Nevertheless, during their design and development, consideration was given to the possibility of
repairs being made by the end user, if necessary.
In general, it is recommended that end users do not try repair printed circuit boards. Spare circuit
boards may be ordered from
SMAR
whenever necessary. Refer to the item “Returning Materials” at
the end of this Section.
SYMPTOM PROBABLE SOURCE OF PROBLEM
NO COMMUNICATION
ƒ
Transmitter Connections
Check wiring polarity and continuity.
Check for shorts or ground loops.
Check if the power supply connector is connected to main board.
Check if the shield is not used as a conductor.
It should be grounded at one end only.
ƒ
Power Supply
Check power supply output. The voltage must be between 9 - 32 VDC at the
LD303
terminals. Noise and ripple
should be within the following limits:
a) 16 mV peak to peak from 7.8 to 39 KHz.
b) 2 V peak to peak from 47 to 63 Hz for non-intrinsic safety applications and 0.2 V for intrinsic safety
applications.
c) 1.6 V peak to peak from 3.9 MHz to 125 MHz.
ƒ
Network Connection
Check that the topology is correct and all devices are connected in parallel.
Check that two Terminators are OK and correctly positioned.
Check that the coupler connections are OK and correctly positioned.
Check that the Terminators are according to the specifications.
Check length of trunk and spurs.
Check spacing between couplers.
ƒ
Network Configuration
Make sure that device address is configured correctly.
ƒ
Electronic Circuit Failure
Check the main board for defect by replacing it with a spare one.
INCORRECT READING
ƒ
Transmitter Connections
Check for intermittent short circuits, open circuits and grounding problems.
Check if the sensor is correctly connected to the
LD303
terminal block.
ƒ
Noise, Oscillation
Adjust damping
Check grounding of the transmitters housing.
Check that the shielding of the wires between transmitter / panel is grounded only in one end.
ƒ
Sensor
Check the sensor operation; it shall be within its characteristics.
Check sensor type; it shall be the type and standard that the
LD303
has been configured to.
Check if process is within the range of the sensor and the
LD303
.
Table 4.1 - Messages of Errors and Potential Cause