Vaisala DMT152 - Manual (Page 28)

User's Guide _______________________________________________________________________
26 ___________________________________________________________________ M210865EN-F
DSC74B Two Pressure Sampling Cell
The DSC74B and DSC74C sampling cells are enhanced versions of the
DSC74. The body is designed in a way that it is possible to measure at
both system pressure and atmospheric pressure.
The DSC74B limits the flow rate with a fixed leak screw. The flow is
optimized for pressures 3 ... 10 barg. The fixed leak screw eliminates the
risk of opening the leak screw fully by accident and this way emptying a
gas vessel. The maximum flow can be increased, if needed, by removing
the leak screw and adjusting the flow manually with the valve. Harmful
gases can be recovered by connecting a collection system at the outlet
(not available from Vaisala).
In the basic operation of the DSC74B, the gas flows to the sensor from
the front and the outlet is on the side. To have the measurement done at
atmospheric pressure, the inlet and outlet are reversed. Then the reducing
parts supplied (G3/8" - G1/2" or G3/8" - G1/4") on the outlet side help to
protect the sensor from ambient humidity coming in.
DSC74B parts are:
- Sampling cell, thread 3/8"G
- Connection part with a needle valve and an integrated leak screw
- Reducing Nipple (thread adapter), G3/8" - G1/2"
- Reducing Adapter (thread adapter), G3/8" - G1/4"
0510-032
Figure 14 DSC74B
1 = Gas goes in
2 = Gas comes out