  • Alarms for variable area flow meters
• Model NK

### Flow meter accuracy

Kytola flow meter accuracy is stated as % of F.S. (Full Scale) or % of RD (Reading).

 % F.S. accuracy
E.g. when flow meter full scale is 100 L/min and accuracy is stated as +/- 5 % F.S. it means +/- 5 L/min accuracy on the flow meter whole measurement range.

% of F.S. inaccuracy is calculated

Flow meter reading – Real flow            *100 = F.S. inaccuracy
Flow meter full scale

 % RD accuracy
E.g. when flow meter reading is 100 L/min and accuracy is stated as +/- 5 % RD it means +/- 5 L/min accuracy. Or at 50 L/min reading +/- 2,5 L/min accuracy.

% of RD. inaccuracy is calculated

Flow meter reading – Real flow           *100 = RD inaccuracy

### Gas Flow Meter Calculation Formulas

 Gas flow conversion formula Actual Flow Rate: Q0 = Actual flow rate ρ0 =Specific gravity of measured gas (Air = 1) p0 = Actual ABSOLUTE pressure in metering tube T0 = Actual ABSOLUTE temperature (Kelvin) in metering tube (0°C = 273,15°K) (20° C = 293,15°K) Flowmeter Design (Calibration) Conditions Q1 = Flow meter reading ρ1 = Specific gravity of design gas (Air = 1) p1 = ABSOLUTE design pressure (calibration pressure) T1 = ABSOLUTE design temperature(Calibration temperature)

Example 1

What is the maximum flow if flow meter EK-3NR is used for Carbon dioxide at 3 bar(g) / 25°C.

Ex-3NR scale is

• 1 - 12 ln/min Air at 0 bar(g)/ 20°C

Q1 = 12 ln/min
ρ1 = 1
p1 = (0 + 1,013) bar = 1,013 bar
T1 = 293,15° K

Q0 = ?
ρ0 = 1,529
p0 = (3+ 1,013) bar = 4,013 bar
T0 = 298,15° K Actual flow at 12 ln/min reading
Q0 = 19,15 ln/min CO2 at 3 bar(g)/ 25°C

Example 2

What is the actual flow if flow meter LH-JJ32 is used for Helium at 5 bar(g) / 10°C.

LH-JJ32 is calibrated for

• 30 ln/min Nitrogen at 3 bar(g)/ 20°C

Q1 = 30 ln/min
ρ1 = 0,9672
p1 = (3 + 1,013) bar = 4,013 bar
T1 = 293,15°K

Q0 = ?
ρ0 = 0,1380
p0 = (5+ 1,013) bar = 6,013 bar
T0= 283,15°K Actual flow at 30 ln/min reading
Q0 = 98,9 ln/min He at 5 bar(g)/ 10°C 