Detcon DM-700 - Manual (Page 38)

Model DM-700
DM-700 Instruction Manual Rev. 4.0 Page 34 of 48
 Verify Power source is stable.
 Verify field wiring is properly shielded and grounded.
 Contact Detcon to optimize shielding and grounding.
 Add Detcon’s RFI Protection Circuit accessory if problem is proven RFI induced.
Nuisance Alarms
Check condulet for accumulated water and abnormal corrosion on terminal blocks.
If nuisance alarms are happening at night, suspect condensation in condulet.
 Add or replace Detcon’s Condensation Prevention Packet P/N 960-202200-000.
 Investigate the presence of other target gasses that are causing cross-interference signals.
 Determine if cause is RFI induced.
Processor and/or Memory Faults
 Recycle power in attempt to clear problem
 Restore Factory Defaults - This will clear the processor’s memory and may correct problem.
 Remember to re-enter all customer settings for range and cal gas level after Restore Factory Defaults.
 If problem persists, replace the Intelligent Transmitter Module.
Unreadable Display
If due to excessive sunlight, install a sunshade to reduce glare.
Nothing Displayed – Transmitter not Responding
 Verify condulet has no accumulated water or abnormal corrosion.
 Verify required DC power is applied to correct terminals.
 Swap with a known-good ITM to determine if ITM is faulty.
Faulty 4-20 mA Output
If Sensor has a normal reading with no Faults displayed, and the 4-20 mA signal output is 0mA….
 Check that wiring is properly connected at terminal blocks and through to controller inputs.
 The 4-20 output loop must be closed (resistance of < 1000 ohms) to avoid the Loop Fault.
 Perform a “Signal Output Check” sequence via Section 3.5.5 and verify 4-20mA output with Current
Meter.
 Swap with new ITM to determine if the ITM’s 4-20mA output circuit is faulty. If the 4-20mA current
loop is still out of tolerance, contact Detcon at [email protected] , or contact Detcon customer
service.
No Communication - RS-485 Modbus™
If sensor has a normal reading with no Faults displayed and the Modbus™ is not communicating….
 Verify that the correct (and non-duplicated) serial address is entered (per Section 3.5.3).
 Check that the wiring is properly connected at terminal blocks, and the serial loop is wired correctly.
 Perform a “Signal Output Check” per Section 3.5.5 and troubleshoot wiring.
 Consider adding a Modbus™ repeater if the distance from the nearest distribution drop is excessive.
 Swap with new ITM to determine if the ITM’s serial output circuit is faulty.
 Refer to Detcon’s “Guide to Proper Modbus™ Communications” Application Note.