Installation Manual

32
4 Troubleshooting
The DVP-120 is tested at the factory for reliable operation. Most problems can be traced to the set-up of configurable features and
modes, system wiring or trouble with the sensors.
! WARNING
Do not disassemble unit or attempt to repair or modify any component of this instrument. This instrument contains no user serviceable parts, and
substitution of components may adversely affect product performance and result in sickness or death.
4.1 System Status Light Flashing
The system status light (section 3 Operation) is normally green indicating power is present, but will change to yellow whenever the
controlling firmware detects a Trouble condition. Possible trouble conditions are:
– Any configured channel has less than 4 mA flowing in the current loop
– A sensor is reporting a trouble condition
– Any configured channel wiring is open.
– Internal controller board problems are detected.
4.1.1 Input Channel Trouble
Any time the POWER light is yellow, the first thing the technician should consider is that one of the input channels is in trouble.
Reviewing the Sensor Status displays (using the up and down keys), should reveal which channel has a problem since the gas reading
will be replaced with the word TROUBLE. Be sure that the 4-20mA output on each sensor is set to “On”.
4.1.1.1 No Sensor
A common source of a trouble condition is an input channel that is configured for a sensor that does not exist. In this case, the system
expects to see current flowing within the current loop, but there cannot be current if there is no sensor connected. Either fix the miss-
wired sensor, or change the sensor type to NONE, section 3.3.2.2. After returning to normal mode (using the MENU key), the power
light should return to steady green. Be sure that the 4-20mA output on each sensor is set to “On”.
4.1.1.2 Wrong Sensor Type
If all channels are configured properly, another source a trouble condition could be the type of sensor attached to an input channel.
Macurco™ Toxic sensors can indicate high gas concentrations with signals of up to 24 mA in the current loop. However, a combustible
sensor can indicate a trouble condition with a 21 mA signal. Therefore, a toxic sensor connected to channel which is configured for a
combustible sensor can cause a fault indication if the gas concentration is high enough.
4.1.1.3 Sensor Trouble
All Macurco™ Sensors are either supplied with a STATUS lamp that will indicate the health of the device, or will display a trouble
condition on the digital display. Macurco sensors may be tested by depressing the TEST button on the sensor printed circuit board, or
(depending on the type of sensor), the button on the interior front panel of the unit. Macurco sensors will step the output current level
from 4 mA to 20 mA over the course of the warm-up period, allowing the technician to determine where the trouble condition exists. If
the sensor is still in a trouble condition, resetting the power may clear the trouble condition. Remove one of the power wires from the
sensor terminal strip causing the sensor to go through a power-up reboot. Be sure that the 4-20mA output on each sensor is set to
“On”.
4.1.1.4 Faulty Wiring
Finally, the wiring between the DVP-120 and the sensor should be investigated. The power input to the sensor should be investigated
at the sensor. Since Macurco sensors are rated for operation between 12 and 24 VDC or VAC, the voltage drop between the DVP-120
and the sensor should not be an issue if the wiring guidelines in Table 2-2 are followed. A multi-meter can be inserted to check the
current flow within the loop, or a continuity test can be performed on all four wires between the DVP-120 and the sensor. Ensure power
is removed from the DVP-120 prior to removing the input or output connectors from the DVP-120 controller board. Be sure that the 4-
20mA output on each sensor is set to “On”.