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Rotameter Guide & FAQ's


Low Flow Tube
High Flow Tube
  Low Flow Tube
High Flow Tube

Direct Read

(full scale)
FM-1050 BR
FM-1050 SS
0.13-104 SCCM  2.4-44 SLPM         No  +/- 5%
FM-1000 BR
FM-1000 SS
10-130 SCCM  5-70 SLPM   0.02-0.24 SCFH  10-150 SCFH    Yes  +/- 5%
PG-1000 BR
PG-1000 SS
2.5-25 SCCM  0.5-5 SLPM   0.01-0.06 SCFH  1-10 SCFH   Yes  +/- 10%
PM-1000 BR
PM-1000 SS
 0.1-1.2 SLPM  10-55 SLPM   0.2-2.6 SCFH   20-120 SCFH   Yes  +/- 10%
FM-1127 BR
FM-1127 SS
 5-120 SLPM  20-500 SLPM   0.2-4 SCFM  1-16 SCFM   Yes  +/- 10%
FM-1100 BR
FM-1100 SS
10-120 SLPM   50-500 SLPM   0.5-4 SCFM
 1-15 SCFM   Yes  +/- 10%

*All air flow rates at 70°F and 14.7 psia


Basic Flowmeter Principles


Rotameter Calibration Charts (FM-1050)

Correction Factors

Rotameter Pressure Correction Factors

Rotameter Temperature Correction Factors

Rotameter Gas Correction Factors

Engineering Drawings

Engineering Drawings, Rotameters


Instructions, FM-1000/FM-1050


• How do I read the ball in the tube?
  Take the reading from the middle of the ball.

• How do I take a reading with two balls in the tube?
   Read the top ball until it goes above the top of the chart, then read the lower ball. (The black ball is glass and the silver ball is stainless steel)


• Why are there two balls in the FM-1050 tube?
   The flow range of the tube is extended with two balls instead of one.

• What are the units for 0-150 scale on the FM-1050?
   The 0-150 scale is in millimeters. Calibration charts for the specific gas and pressure can be found at:
   Rotameter Calibration Charts (FM-1050)

• Should I have the valve on the inlet or the outlet of the rotameter?
The valve should be on the inlet when the gas is to be used at atmospheric pressure.  The valve should be on the outlet if there is a vacuum or varying pressure downstream.

• Why are there different FM-1050 calibration charts for different pressures?
The pressure that you choose is the pressure that is in the tube.  Most people have the valve on the inlet and the rotameter flows to an instrument or process at atmospheric pressure so in that case you would use the 0 PSIG charts.  Do not use the pressure supplying the rotameter if the valve is on inlet. If your valve is on outlet of the rotameter then either use a pressure correction factor or use a calibration chart corresponding to the pressure in the tube. We have many charts that are for 20 PSIG and 50 PSIG.
   Rotameter Calibration Charts (FM-1050)



• What do I do when the two balls in the FM-1050 tube stick together?
   It most likely means that your rotameter needs to be cleaned. Please see the FM-1000/FM-1050 Instructions for cleaning procedures. It could also be that there was a sudden surge of pressure to the rotameter.

• Where do I find rotameter spare parts?
  Click here.

• Can my  rotameter that has an air scale be used with other gases?
   Yes, as long as he rotameter materials are compatible with the gas.  You will need to use a Gas Correction Factor Chart to get an approximate flow rate.

Rotameter Gas Correction Factors

• Can I get a direct read scale for the FM-1050 Rotameter?
   Yes, We have many direct read scales available for the FM-1050.  Please Contact Us with the flow range, gas, and pressure desired and we will try to find a tube that fits your application.

• How do I get a +/- 1% calibration chart for my FM-1050 (reference/150 mm) rotameter?
  You need to order the +/- 1% calibration chart when you order the FM-1050 rotameter (additional charge). Click here.

• Can I get a calibration certificate for my FM-1000/1050 direct read scale?
  You need to order the +/- 5% calibration certificate for your direct read scale when you order the FM-1000/1050 rotameter (additional charge). Click here.

• Do I need a calibration certificate when I order my rotameter?
  FM-1000 and FM-1050 rotameters have an accuracy of +/- 5% full scale.  All other rotameters have an accuracy of +/- 10% full scale.

• What is the pressure and temperature rating for my rotameter?