Delta NANOTRACE DF-745 Instruction Manual download pdf (Page 45)

User Interface DF-745 41

back and change the value or move to the Done button, followed by hitting the Enter key

to leave the screen. Using the ESC key at any time will exit the screen making no changes

and return to the main display.

7.4.3.1.2 Do A Manual Zero

Figure 29: Manual Zero Screen

The manual zero command enables the user to zero the moisture cell in an interactive

manner.

For this purpose, it is necessary to ensure that moisture free gas (sub ppb) is entering the

sensor through the process inlet. When switching to a gas that is moisture free, it is

important to wait a period necessary to allow the reading to re-stabilize.

It is extremely important to note that moisture is inherently slow to move and as a result the

process of doing a zero action can take many hours before the reading is at baseline. A

premature zero, although acceptable, will ultimately result in a negative reading as the

plumbing and analyzer continue to dry out requiring another zero action. See the section on

Active Zero on page 57 for additional information.

After selecting Do a Manual Zero, a screen will appear which displays a trace of the

recent moisture reading. See Figure 29. Observe the trace until the reading is stable and

then press Enter. This action will accept the present value as the new zero setting for the

moisture cell and the Zero Reference field will be updated. After this action, the user will

be brought back to the Check/Adjust Zero screen.

Pressing ESC during the calibration process will abort the action and return to the main

display. Whether the calibration is complete or aborted, pressing Done from the previous

screen will allow the user to return to the main display.

Once complete the gas source must be returned to the original state with process gas going

directly through the sensor.

A relay is available on the Analog Output Setup Screen (see page 55) to signal that a zero

calibration is taking place, and the analog output signal can also be frozen or allowed to

update during the calibration process.

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Delta NANOTRACE DF-745 Instruction Manual Page 45