Specifications

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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.
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 3.3.3.2. After returning to normal mode
(using the MENU key), the power light should return to steady green.
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. 3M™ Macurco™ Toxic Sensors can indicate high gas
concentrations with signals of up to 24mA in the current loop. However, a combustible sensor can indicate a trouble condition with a 21mA 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 3M™ 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. 3M™ 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. 3M™
Macurco™ Sensors will step the output current level from 4mA to 20mA 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.
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 3M™ Macurco™ Sensors are
rated for operation between 12 and 24VDC 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.
4.1.1.5 Resettable Fuse
Each sensor channel is provided with a PTC-resettable fuse internal to the DVP-120 to protect against over current situations. To reset a sensor channel, power should be removed from the
channel. This can be accomplished by removing power from the sensor – causing the loop current to go to zero, or by completely removing power from the DVP-120.
4.1.2 Internal Controller Board Trouble
If the sensor status display and investigative efforts reveal no problems with the input channel current loops and channel configuration, the most likely trouble condition is an internal
problem detected by the DVP-120 controller. In this case, contact the 3M Macurco Technical Service for advice and help.
4.2 Timed ventilation problem
When using the timed ventilation mode, the system clock should be checked regularly (at least twice a year). The battery backed real time clock in the DVP-120 does not adjust for daylight
saving time so the spring and fall switch over points are good choices to check the system clock.
W WARNING
Highvoltageterminals(120/240VAC)arelocatedwithintheDVP-120,presentingahazardtoservicetechnicians.OnlyqualiedtechniciansshouldopentheDVP-120caseandservice
the internal circuits. Ensure power is removed from the DVP-120 prior to servicing the unit.
4.3 No Power
The DVP-120 starts up as soon as power is applied to the microcontroller, and the DVP-120 is designed to have power continuously applied to the unit. An external indication of successful
power application to the unit is the immediate operation of the Status Lamps grouped around the LCD. If the operator does not see immediate response from the status lamps, power
should be checked at AC~ (refer to Figure 1-2 for connector locations).
If the correct voltage is noted at AC~, then the internal fuse of the DVP-120 should be investigated. The DVP-120 is protected from over-current and transient situations by the fuse at F3.
AFTER removing power from the DVP-120, F3 can be checked by removing the safety cover. If necessary, replace F3 with a 5x20 mm SLO-BLO® fuse with a rating of 1 Amp 250V, e.g.
Littelfuse™ P/N 218001. Be sure to REPLACE THE SAFETY COVER on F3 before re-applying power to the DVP-120.
W WARNING
DVP-120maynotfunctioneffectivelybelow32°F(0°C).Usingtheinstrumentbelowthistemperaturemayadverselyaffectproductperformanceandresult in sickness or death.
4.4 LCD Display unreadable
It is possible that the LCD is unreadable due to temperature or aging of the control panel. If this is the case the following steps should rectify the problem:
- Hold the MENU key for three (3) seconds.
After three seconds, the power led will turn red. After two additional seconds, the LCD backlight will also be turned off.
- Press the UP and DOWN cursor keys to change the LCD contrast.
Each press of the UP or DOWN cursor key will change the contrast by a step in that direction. Adjust the contrast for best viewing.
- Press any other key to exit the contrast-setting mode.
4.5 The Keypad does not respond (LCD shows KEYS LOCKED)
The keypad can be unlocked by holding the zero (0) key for three seconds. At this time the backlight will turn on and the display will return to normal mode.
The keypad can again be locked by holding the zero key for three seconds, until the display shows KEYS LOCKED.
4.6 The Keypad does not respond after silencing an Alarm, Warning or Trouble.
LCD continues to show the Alarm, Warning or Trouble message.
It is possible that the horn or strobe have been configured to respond in alarm, warning or trouble conditions, even though there is no horn or strobe connected (or perhaps they are used
for some purpose that is not audible or visible).
First,holdtheHUSHkeyforveseconds,oruntilthedisplaychangesto“ALARMsilencedfor5minutes”orotherrelevantmessage.
Second, use the configuration menu to disable the horn or strobe, if they are not being used for some other purpose.