PASCO PS-2222 General Flow Sensor - Manual (Page 4)

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G e n e r a l F l o w S e n s o r C r i t i c a l U s e C o n s i d e r a t i o n s
4
For low flow Venturi measurements at a rate of 1 standard cubic foot per minute (SCFM), the measured value of
P
diff
was approximately 11 pascals (Pa) and the theoretical P
diff
was 6 Pa. These are uncorrected values with a
baseline noise level of approximately 3 Pa. Repeatability is excellent with a variation within the noise band.
General Flow Sensor with the Venturi Tube and Pitot Tube
Critical Use Considerations
Maximum Operating Pressure
Do not subject the sensor to gauge pressures greater than 29 pounds per square inch (psi) or 200 kilopascals
(kPa) as permanent damage will occur. Do not use the sensor to measure flow in systems pressurized to more
than 29 psi. Note that municipal water systems normally exceed this value.
Maximum Differential Pressure
The maximum differential operating pressure between the high pressure and low pressure input is 7.25 psi or
50 kPa. Differential pressures greater than 7.25 psi may result in permanent damage to the sensor causing inaccu-
rate measurement.
High Pressure/Low Pressure Reversal
Operation of the sensor with reversed pressure applied (the pressure applied to the low pressure port is higher
than the pressure applied to the high pressure port) may result in permanent damage to the sensor.
Changing Fluid Use
Care must be taken when changing from measurement in liquids to measurement in gases. It is normal for small
amounts of liquid to migrate into the hoses during use. This may be minimized by insuring that the hoses are
tightly attached to the sensor prior to introducing liquids to the system. The large diameter of the venturi and
pitot tube hoses minimizes capillary flow. Placing a high point in the hoses above the fluid level in the systems
will also help limit fluid migration.
After fluid use, hoses from the Venturi or Pitot Tube should be carefully blown clear of any migrated fluid and
dried prior to use measuring a gas such as air. Fluid left in the line may obstruct flow causing inaccurate measure-
ment. Fluid may also vaporize during use causing inaccurate measurement of flow.
Item Value
Range: 0 to 50 kPa Differential Pressure
Accuracy: ±2.5% of Full Scale (at 50 kPa)
• Venturi Tube in Water ±2.1 gallons per minute (gpm)
• Venturi Tube in Air ±2.5 scfm
Repeatability: 0.25% of Full Scale (at 50 kPa)
Resolution: 0.02% of Full Scale
Item Value with Venturi Tube Value with Pitot Tube
Range - Water:
0 to 0.00530 m
3
/s (0 to 84 gpm)
0 to 9.98 m/s (0 to 22.3 miles per hour)
Range - Air: 0 to 0.0488 m 3 /s (0 to 773 gpm) 0 to 92.1 m/s (0 to 206 mph)