Emerson I-0021 Manuel D’Utilisation

90003482(2) [NGA-e (MLT-Software 3.2.X)] 07/98

NGA 2000

↓↓

Analyzer module setup

↓↓

Differential measurement

↓↓

In the menu "Differential Measurement" you can measure the difference between the
current concentration and a reference concentration of the same gas component. That
means, the measurement value is not based on the zero value as it is usual for an
absolute value measurement. Instead of this the signal will be compared with defined
concentration of the component selected. That may be useful for concentrations that only
differ a little from the basic value of this component in the measurement environment
(Example: CO

2

 of plant in air).

If you want to make a differential measurement for other components, you can change to
the other channels of an MLT analyzer or analyzer module with the F3 key.

Condition:

♦ 

You have to calibrate with zero gas and to linearize the measurement channel and the
reference channel.

• 

To calibrate see 4.5 p. 4-39 and 4.6 p. 4-43 or 5.1.1 p. 5-15 to 5-17.

• 

To linearize see 5.1.5 p. 5-33

Differential measurement:
1) Disable the function:

• 

Press the 

88 

 -key or the 

→

→

 -key in the line "Function is" to select the parameter and

adjust "Disabled" with the 

↑↑

 -key or the 

↓↓

 -key. Confirm it with the 

88 

 -key.

• 

This is necessary to avoid interference of values while the parameters where determined.

• 

Change to the menu line "Choose source channel..." with the 

↓↓

 -key and press the

88 

 -key or the 

→

→

 -key to go to the submenu "Channels":

Measure

Channel

Back...

TAG

95.00 ppm

-- Differential Measurement --

Function is:

Disabled

Source concentration:

Use actual value

Store source concentration !

Source channel:

Choose source channel...

[2nd menu page via F5 (More...)]