Teledyne HFC-E-202 User Manual download pdf (Page 13)

HFM-E-200/HFC-E-202

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3.4. Shunt:

Measurement of flow rates higher than the 10 sccm full scale is achieved by dividing the flow with a

fixed ratio shunting arrangement, as is illustrated in Figure 3.3. This is accomplished by placing the

measuring capillary tube parallel with one or more dimensionally similar channels, called a laminar flow

element (LFE). Therefore, the sensor only needs to heat the gas passing through the capillary tube

resulting in low power requirements, while retaining all the mass measuring characteristics.

The HFM-E-200/HFC-E-202 series has many different shunts. The low range shunt consists of tubes

inserted into a cylindrical base. This shunt is adjustable for ranges from 0-10 sccm to 0-180 sccm (see

Figure 3.4). The medium range shunts consists of a piece of stainless steel foil welded to a solid steel

center core. The high range shunts consists of a corrugated stainless steel ribbon wound into a coil and

fused.

Figure 3.2

Figure 3.4

Figure 3.3

Figure 3.5

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Teledyne HFC-E-202 User Manual Page 13