Detcon 972-041170-00L - Manual (Page 5)

Assure that all field tubing connections are secure by obstructing the end of the sample line and observ-
ing that the flow meter decreases to “0” flow.
1.3 FLOW FAULT DETECTION
Flow fault detection consists of a flow fault circuit assembly located inside the enclosure and a door mount-
ed fault indicator lamp. If the air flow falls below a predetermined set point the following will occur: the
flow fault alarm relays will energize; an LED indicator mounted on the flow fault PCB will illuminate; the
door mounted flow fault lamp will illuminate; the 4-20mA signal will be opened via relay #1 on the flow
fault circuit board (this will allow for flow fault programming at the remote recording device or computer.
Because the pressure inside the sample and vent flow tubing differs according to the tubing length , the
flow fault circuit will require calibration after installation.
To calibrate the flow fault circuit, first determine at what point it is desired that the flow fault circuit is
activated. Typically, air flow should range between 500 and 1000 ml/min. (milliliters per minute) as seen
on the flow meter located on the left of the enclosure. It is recommended that the flow fault circuit be set to
activate at a flow of approximately 300 ml/m.
To adjust the flow fault first set the air flow at the point where you want the fault condition to activate.
Next turn the flow fault adjust potentiometer (PT1 as seen in the illustration on the previous page) clock-
wise until the flow fault LED illuminates and its relays fire. Make adjustments as necessary by increasing
and decreasing airflow until the flow fault function occurs at the desired set point. Once the flow fault cir-
cuit has been set, return the air flow to between 500 and 1000 ml/m.
NOTE: Because sample and vent tubing can become congested over a period of time, the flow fault func-
tion should be checked periodically and adjusted if necessary.
1.4 CALIBRATION
Model 972-041170-00L sensor assemblies are calibrated prior to shipment and should therefore require
minimal adjustment at time of commissioning. However, it is recommended that a complete calibration be
performed on a periodic basis to assure optimum system performance. Refer to the sensor instruction man-
ual for gas type, range and sensor specific calibration instructions.
Note that the sensor instruction manual requires the removal of rain/splash guards for the application
of gas. This requirement will be superceded by the instructions below. The calibration adapter attached to
the sensor head should not be removed during calibration.
Required material:
1. Span gas cylinder containing gas as per instructions in the sensor instruction manual(s).
2. 1/4" Tee tubing fitting as shown in the illustratin on the following page.
To Calibrate: (refer to illustration on the following page)
1. Turn the 3-way valve so that the arrow is pointing down. Sample is now being drawn from the CAL port.
2. Using the 1/4" Tee assembly, connect the span gas cylinder for sensor #1 to the calibration port. Note
that the cylinder flow rate should be 1000 ml/m while the sample draw flow rate should be adjusted to 500
ml/m. This will assure that the sample is not diluted.
3. Follow the calibration instructions given in the sensor instruction manual.
4. Close cylinder valve to allow clearing/zero stability. Note that zero and span functions may interact
slightly with one another. Zero and span tests may be repeated 2 or 3 times as necessary.
5. Repeat steps 2 through 4 for the sensor #2.
6. When calibration is complete turn the 3-way valve so that the arrow is pointing up.
Detcon Model 972-041170-00L Gas Detection System PG.5