Vaisala DRYCAP DM70 User's Guide download pdf (Page 65)

Chapter 8 ____________________________Measuring Moisture in SFB6B Gas-insulated Equipment

With DSC74B, the dewpoint can be measured at the GIE pressure. If

the measurement is done in the GIE pressure, DM70 is able to show

the corresponding dewpoint in the atmospheric pressure.

DSC74B limits the flow rate with a leakage screw. The flow rate is

optimized for GIE pressures between 3 ... 10 bar

, and no external

flow meter is needed. The maximum flow can also be increased by

removing the leak screw and adjusting the flow manually with the

valve. To remove the leak screw, see Figure 30 below.

0405-012

Figure 30 Removing the Leak Screw

Parts per million by volume (ppm

) and parts per million by weight

(ppm

) are frequently used to indicate humidity. The latter depends on

the molecular weight of the gas. For SF

, the molecular weight is

146.06, and the conversion between ppm

and ppm

is the following:

ppm

= ppm

/ 8.1

DM70 is able to show the ppm

and ppm

values for moisture.

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Vaisala DRYCAP DM70 User's Guide Page 65