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The ST50 Series Flow Meters are an accurate, easy to install, no moving parts mass flow meter solution. Model ST50 is used for compressed air and nitrogen flow. Model ST51 is used for measuring biogas, digester gas, methane and natural gas. The ST50 Series utilizes FCI proven thermal dispersion technology to provide direct mass flow measurement resulting in higher performance at a lower cost than orifice plates, DP, Vortex shedding and other thermal devices. The meter installs in line sizes ranging from 2 to 24 inches [51 to 610mm] with 1/2″ or 3/4″ NPT.

The ST50 Series uses precision, lithography structured platinum RTD sensors embedded in FCI’s equal mass small diameter, all metal thermowells. Combined with microprocessor electronics and precision calibration, the ST50 achieves excellent accuracy, fast response and virtually maintenance free operation.


Landfill Gas Recovery (LMG)
Wastewater Treatment Plant Digester
Coal Mine Methane Recovery
Livestock and Dairy Farm
On-Farm Biogas Recovery
Biogas: Biomass Fermentation and Recovery
Biomass Gasification
Air/Compressed Air with totalized flow


Media Compatibilty Biogas, Digester Gas, Methane, Methane Composition Gases, Natural Gas, Air, Compressed Air, Nitrogen
Agency Approvals FM/CSA Class 1, Div.1, Groups B,C,D, Class 1, Div.2, Groups A,B,C,D; T4
ATEX/IEC EX(IEC EX: ST51 only) Zone 1
II 2 G Ex d IIC T6…T3,
II 2 D Ex tD A21 IP67
Output Signals
Dual 4-20 mA Analog
0-500 Hz pulse for totalizer
Digital Display (optional) LCD, 2 line x 16 Characters. First line is flow rate and engineering units. Second line user selectable
as temperature or flow totalizer, or alternating.


Pipe/Line Size Compatibility: 2″ to 24″ [51 mm to 610 mm]
Flow Rate:
 ST50: 0.75 to 400 sfps [0.23 to 122 mps]
 ST51: 0.3   to 400 sfps [0.08 to 122 mps]
Accuracy: (at calibrated conditions)
 Standard: ± 2% reading, ± 0.5% full scale
 Optional:  ± 1% reading, ± 0.5% full scale
 Temperature Coefficient: (at calibrated conditions)
With optional extended temperature compensation. Valid from 10% to 100% of full-scale calibration
Flow: Maximum ± 0.025% of reading/ºF up to 250ºF [±0.05% of reading/ºC up to 121 ºC]
Repeatability: ± 0.5% reading
Temperature Compensation: 
 Standard: 40° to 100° F [4° to 38° C];
 Optional:  0° to 250° F [-18° to 121° C]
Turndown Ratio: 10:1 to 100:1


Installation: Insertion
Type: Thermal Dispersion
Material of Construction: 316 stainless steel body with Hastelloy C thermowell sensors, 316 stainless steel compression fitting with teflon or stainless steel ferrule.
Pressure (Maximum Operating without Damage): 
 Stainless steel ferrule: 500 psig [34 bar(g)]
 Teflon ferrule: 150 psig [10 bar(g)]
Operating Temperature: 
 Stainless steel ferrule: 0° to 250° F [-18° to 121° C]
 Teflon ferrule: 0° to 200° F [-18° to 93° C]
Process Connection: 1/2″ MNPT or 3/4″ MNPT with stainless steel or Teflon ferrule.
Insertion Length (Field Adjustable) 1:
 1 to 6 inches [25 to 152 mm]
 1 to 12 inches [25 to 305 mm]
 1 to 18 inches [25 to 457 mm]


Enclosure: NEMA4X (IP67) aluminum, Epoxy coated
Operating Temperature: 0° to 140° F [-18° to 60° C]
Input Power: 
 DC:18 to 36 Vdc
 AC:85 to 265 Vac (CE Mark Approval from 100 to 240 Vac).
Communication Port: RS-232C, Wireless IR to PDA with optional digital display models
Installation: Integral or Remote (50′[15m] max.)