Low Flow Meters for Gas
Rheotherm low gas flow meters provide an easy-to-use technology for measuring gas flow in small lines – typically 1” or smaller at flow rates from a few hundred SCFM down to 25 SCCM. (For flow measurement in larger pipes and ducts, click here). These meters give a repeatable reading in mass or standard volume with no external temperature or pressure correction needed. With no mechanical parts, they are reliable and easy to maintain. Options for hazardous locations (intrinsically safe/explosion-proof) are available.
What Can We Measure?
Continuous flow of most gases, including corrosive and explosive gases. Our flow meters have been used for everything from hydrogen to uranium hexafluoride. Electropolished sensors are available for ultrahigh purity gases. Our applications section has a complete list of fluids we have measured. Contact Us about any application you have or use the form on this page to tell us about your application.
How Are They Installed?
These are in-line flow sensors typically installed with standard tube fittings, but optionally available with flanges, sanitary fittings, etc. Any orientation is acceptable, except vertical with downward flow. With some models the electronics are integral to the sensor, and other models have a separate electronics enclosure to install, up to 200 feet from the sensor.
What Is the Turndown Ratio?
Typical calibration ranges are 10:1 (options up to 200:1), with good accuracy over the entire range. The sensors cannot be damaged by overranging.
How Do They Work?
Our low flow meters use either a straight-through or looped flow tube with a heated and an unheated RTD attached to the outside of the tube. The temperature differential between the two RTDs provides the primary flow signal. At high flow rates the differential is lower because heat is removed more readily. At low flow rates the differential is higher, because less heat is removed. Nothing touches the fluid except the flow tube wall, and there are no mechanical parts to wear, stick or break.
How Do I Get One?
Submit your Rheotherm inquiry today using the form on this page so we can review your application and prepare your quotation. You can also call or visit our Contact Us page for telephone, fax and email information.
- No moving parts
- Exclusive inline TU sensor
- Advanced signal processing electronics
- Field adjustable
- Easy installation
- Choice of wetted materials
- Long-term reliability
|Temperature||Process: 0 – 140°F
(-18 – 60°C)
Environment: 0 – 120°F
(-18 – 50°C)
| -20 – 350°F
(-30 – 175°C)
|Pressure||0 – 1,000 PSI||Up to 30,000 PSI|
|– Up to 200:1 turndown
– Four calibration channels available (for multiple flow ranges or different fluids using the same sensor)
|Calibration Accuracy||± 1% of reading typical|
|Response Time|| 1 sec. ; 3 – 5 sec. typ.
(63% of range);
|Time constant/delay option|
|Repeatability||± 0.5% of reading|
(flow range dependent)
1/16”; 1/8”; 3/16”; 1/4”
3/8”; 1/2”; 5/8”; 3/4”; 1”
|Other sizes via fittings/adapters|
Plain tube stubs suitable for compression fittings
– Tri-Clover (Sanitary);
– SS Flange (1/2” – 2”):
Most other fittings available
|Wetted Material||316 SS||– Hastelloy C-276®;
– Alloy 20;
|Display||2 X16 backlit LCD with selectable display of:
– Mass/volume flow rate
– Total accumulated flow
Integrated Electronics: NEMA 4X Cast Aluminum
Remote Electronics: NEMA 4
|Sensor: Stainless steel
– Stainless steel
– NEMA 7 Explosion-proof
|Hazardous Environment||Integrated electronics:
– Class I, Div. 1, Groups B,C,D
– Class I, Zone 1, IIB+H2 (US)
– Class II, Div. 1, Groups E, F, G
– Class III, Div. 1
Same as above except addition of Group A using ISB
|Outputs||4 – 20 mA (flow rate) or Serial Burst with Flow Rate, Totalizer, and Fluid Temperature||– 0 – 10 or 0 – 5 VDC;
– Pulse (5 VDC open collector);
– HART (4-20 mA);
– SPDT relay;
– 4 to 20 mA temp
|Input Power||24 VDC ±4V
(200 mA; 300 mA w/display option)
|110/230 VAC ±10V|
Inline Sensor Flow Capacities for Gases
|FLOW RATE LIMITS||C||1/16||1/8||3/16||1/4||3/8||1/2||5/8||3/4||1|