SMAR DT302, Owner'S Operation And Maintenance Manual

Page: 59 / 84

Section 4
4.1
MAINTENANCE PROCEDURES
General
DT302
Concentration/ Density transmitters 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 by the end user, if necessary.
In general, it is recommended that end users do not try to repair printed circuit boards. Spare circuit
boards may be ordered from Smar
whenever necessary.
The
DT302 has been designed to operate for many years without malfunctions. The process
application can require periodic cleaning of the repeater diaphragms, and then the flanges may be
easily removed and reinstalled. The transmitter eventually can require maintenance, and then it may
be changed in the field. In this case, the possibly damaged sensor should be returned to Smar
for
evaluation and, if necessary, repair. Refer to the item "Returning Materials" at the end of this
Section. The table 4.1 shows the symptoms and the probable source of problem cause:
SYMPTOM PROBABLE SOURCE OF PROBLEM
NO COMMUNICATION

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.

Power Supply
Check power supply output. The voltage must be between 9 - 32 VDC at
the
DT302 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 application.
c) 1.6 V peak to peak from 3.9 MHz to 125 MHz.

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 Terminators are according to the specifications.
Check length of trunk and spurs.
Check spacing between couplers.

Network Configuration
Check the network communication configuration.

Electronic Circuit Failure
Check the main board for defect by replacing it with a spare one.
INCORRECT READING

Transmitter Connections
Check for intermittent short circuits, open circuits and grounding
problems.
Check if the sensor is correctly connected to the
DT302 terminal block.

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.

Sensor
Check the sensor operation; it shall be within its characteristics.
Check sensor type; it shall be the type and standard that the
DT302 has
been configured to.
Check if process is within the range of the sensor and the
DT302 .
Table 4.1 - Symptoms and Probable Source of Problem