Unit] - Fluke MOLBOX RFM Operation And Maintenance Manual

molbox™ RFM™ OPERATION AND MAINTENANCE MANUAL
The humid air correction applied to the molbloc measured flow is (from ASME
FEDSM98-5309):
To specify the gas flowing through molbloc-S, press [GAS]. The display is:
The display is:
Select the desired gas. Pressing [ENTER] returns to the last run screen with the
newly selected gas active. The selected gas is always displayed in the upper
right hand corner of the MAIN run screen.
If <2Air> is selected,
The display is:
Leave the value at zero when dry air is being flowed. Enter the appropriate non-
zero value (see section immediately above) if humid air is being flowed.
3.4.3

[UNIT]

PURPOSE
To specify the flow unit of measure in which molbox RFM displays measured flow values.
PRINCIPLE
molbox RFM calculates the mass flow of various gases in kilograms/second [kg/s]. molbox
RFM also supports conversions to a variety of other flow units of measure. The UNIT function
allows the user to select the flow unit of measure in which molbox RFM displays measured flow.
These include units of mass flow, including volumetrically based mass flow units (i.e., sccm)
© 1998-2007 DH Instruments, a Fluke Company
q ( ratio
m
If an incorrect value of W is entered (for example, using any non-zero W value
while flowing dry air), an error will be introduced into the air flow
measurement. W, humidity ratio, is different from relative humidity.
OPERATION (molbloc-S operation)
The gas selected on molbox RFM should always be the gas that is flowing
through the molbloc. molbloc/molbox does not use K factors or gas
conversion factors between gases. When calibrating or testing a device with
a surrogate gas, molbox RFM should be set to the surrogate gas. The K
factor or gas conversion factor, if used, defines the relationship between the
surrogate gas and the process gas for the device being tested, not for
molbloc/molbox (see Section 3.4.1 and 3.4.2 PRINCIPLE). The K factor is
supplied by the manufacturer of the device being tested.
Page 34
= + + +
2
) a bW cW dW
where :
=
a . 1 0000
= −
b . 0 336872
=
c . 0 158514
=
d . 0 131924
1N2 2Air
Humidity ratio:
3
0:1