Dwyer DPM - Manual (Page 30)

Particulate Monitoring Systems
Installation & Operating Manual
Document No. 210-1003-M Page 23 ©2007
7. Manual System Zero Check
The System Zero Check is used at installation to confirm proper installation and for troubleshooting.
This check is mostly for control units that are not equipped with the optional self check subsystem.
SAFETY
• Always disconnect power to the control unit before making any wiring
changes at either the control unit or sensor as well as when making any
mounting changes or replacing any component.
• Do not remove the sensor (even when power is disconnected) from a
running process if it will in any way compromise personnel or plant safety.
• All regulatory and plant safety procedures must be followed at all times
while performing any equipment check or maintenance.
• For hazardous area sensors, do not disconnect the external earth ground
strap.
• Do not perform any procedure if it will in any way compromise hazardous
area procedures.
SYSTEM ZERO CHECK
1. Shut the process off, stopping flow completely, including all airflow not just
particulate flow. The slightest amount of flowing particles can create a
signal. If process flow cannot be stopped, the particulate sensor can be
removed from the process and installed in a grounded test pipe to create a
shielded, no flow condition.
2. Let the system stabilize for 2-3 minutes.
3. Read the display. It should be below the control units specified minimum
detection level. If the system passes this check then it is assured that there
are no false signals entering the system.
If the system zero check is not successful, each component of the system should
be checked individually, in the following order:
1. Control Unit Zero Check
2. Coaxial Cable Zero Check
3. Sensor Zero Check