Input Channel Trouble - Macurco DVP-120C User Instructions

Macurco DVP-120C Manual
• 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.

6.1.1 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".
6.1.1.1 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
Sensors Submenu. 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".
6.1.1.2 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.
6.1.1.3 Sensor Trouble
All Macurco™ Sensors are either supplied with a STATUS LED 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".
6.1.1.4 Faulty Wiring
Finally, the wiring between the DVP-120C 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 power supply and the sensor should not be an issue if the wiring guidelines in Table 2
2 are followed. A multimeter 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-120C and the sensor. Ensure power is removed from the DVP-120C
prior to removing the input or output connectors from the DVP-120C controller board. Be sure that the 4-20mA
output on each sensor is set to "On".
6.1.1.5 Resettable Fuse
Each sensor channel is provided with a PTC-resettable fuse internal to the DVP-120C to protect against over current
situations. To reset a sensor channel, power should be removed from the channel. This can be accomplished by
REV – 1.0 [34-8708-4770-8 ]
4.13.3 Configure
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