Dwyer DPM - Manual (Page 35)

Particulate Monitoring Systems
Installation & Operating Manual
Document No. 210-1003-M Page 28 ©2007
8.3 Control Unit Span Check
The Span Check will verify the instrument span calibration. The internal self check subsystem will
automatically perform the following procedure:
1. Electronic disconnect of the particulate sensor cable
2. Electronic input of a calibrated pA reference signal
3. Allow the reading to stabilize
4. Measure the reading and compare to the allowable span tolerance
5. Electronic disconnect of the reference signal
6. Electronic re-connect of the particulate sensor cable and resume normal operation.
There are four independent methods to activate the span check:
Method Description
Power-Up
A span check is automatically performed each time power is applied
to the control unit
Keypad
The operator may activate a span check manually through the control
unit keypad. Reference Menu #2 setup tree for complete details.
Automatic
The control unit may be configured to automatically perform a span
check on a period basis. A re-settable delay timer controls the time
period between self checks. The delay timer is set to 1 hour by default.
The delay timer is reset each time self checks are performed regardless
of the activation method.
Automatic self checks may be activated at preset hourly, daily and
monthly dates/times when connected to a computer running the
FilterWare Visualization application.
Remote
The operator may activate a span check manually when connected to a
remote computer running the FilterWare Visualization application.
Alternately, self checks may be independently activated from any
remote PC or PLC with Modbus® communication capability.
8.4 Sensor Cable Check
Integrity of the sensor cable is checked using advanced digital signal processing algorithms. The cable
check operates continuously and does not interfere with normal monitoring of the process particulate
signal. The sensor cable check is disabled while zero or span checks are being performed.
For proper operation of the sensor cable check a process running signal must be provided to the
control unit. Reference section 8.6 for full details.
8.5 Particulate Sensor Check
Operation of the particulate sensor/probe is checked using advanced digital signal processing
algorithms. The particulate sensor check operates continuously and does not interfere with normal
monitoring of the process particulate signal. The particulate sensor check is disabled while zero or
span checks are being performed.