Specifications

GDC-150 Operation Manual

5209-9000 Rev 0 19

5.6. Setting the Span Gas Value

Step Setting the Span Gas Value Procedure

Move the jumper to position P2 (see Figure 4-1 on page 15). The green

outer LED flashes once for confirmation. The system is now waiting for

the user to set the desired value.

Attach volt meter leads to test points TP1 and TP2 (see Figure 1-4 on

page 3). Alternatively, if the optional LED digital display has been fitted,

read the value indicated on the display.

Use the UP or DOWN push-buttons (see Figure 1-4 on page 3) until the

calculated voltage is displayed on the volt meter (or the optional LED

digital display).

Move the jumper back to its resting position (P1). At this time the new

value is saved and the green LED flashes once for confirmation.

5.7. Calibrating the Null (Zero) Value

Step Calibrating the Null (Zero) Value Procedure

1 Attach a regulator to a cylinder of zero air (or nitrogen).

Insert the calibration adapter into the sensor opening in the front of the

enclosure door. Use a slight twisting motion as you gently push the

calibration adapter into the sensor opening. If the calibration adapter is

hard to insert, moisten the "O" ring slightly then try re-inserting it. If the

transmitter has been fitted with an optional splash guard, remove the

plastic plug from the center of the splash guard to gain access to the

sensor opening. To remove the plastic plug, push inward at the center of

the plug until the edges lift slightly then slip a small flat blade screwdriver

under and pop the plug off.

3 Open the regulator valve fully and allow zero air to flow over sensor.

Move the jumper to position P3 (see Figure 4-1 on page 15). The outer

LED will change to a steady amber color. The system now waits 30

seconds to ensure the user is flowing zero air.

The GDC-150 then enters a count down during which time it adjusts the

null value. The length of this count down period is:

• 90 seconds for catalytic and solid-state sensors

• 60 seconds for electrochemical sensors.

If desired, attach the volt meter leads to test points TP1 and TP2 (see

Figure 1-4 on page 3). The meter will show 0.0 VDC, climb to a higher

value, then slowly descend back to 0.0 VDC indicating the GDC-150 has

null adjusted the circuit. Once the count down is finished, the outer LED

changes back to green indicating the procedure is complete.

6 Move the jumper back to its resting position (P1) and remove the zero air.