Performance

Performance Data

Flow Measurement Uncertainty
Standard: 0.20 % of rate
Enhanced: 0.15 % of rate
Premium: 0.10 % of rate
Low Flow Calibration: 0.10 % of rate – requires RHE 40 Series transmitter
Customized Calibration: Consult factory

Low flow calibration focuses on the range from ½ × Qₙₒₘ downwards to lower flow rates than on other calibrations. Often used for low pressure gas or very viscous liquids. Customized calibration uses specific calibration points according to customer requirements.

Flow Measurement Repeatability
Standard Sensors: ±0.1 % of rate
Premium Sensors: ±0.05 % of rate

Temperature Measurement
Better than ±1 °C

Density Calibration (Liquid)
Standard: ±0.001 kg/l uncertainty
Premium: ±0.0005 kg/l uncertainty – requires High Accuracy or Focused Calibration Option

Reference conditions: 18–24 °C Water @ 1–3 bar

Measurement Tube Pressure Ratings

The maximum pressure (pₘₐₓ) of a sensor is determined by its lowest rated part: the measurement tube (see table below) or the process connection (see corresponding standards or manufacturer information).

For sensors in sealless versions, the material of the process connection is usually the same as the material of the measurement tubes. In special cases, the material may differ.

	50 °C 122 °F	120 °C 248 °F	210 °C 410 °F	350 °C 662 °F
SS 316Ti (standard)	73 bar 1059 psi	66 bar 957 psi	57 bar 827 psi	48 bar 696 psi
Alloy C22	94 bar 1363 psi	83 bar 1204 psi	71 bar 1030 psi	59 bar 856 psi
Super Duplex *	237 bar 3437 psi	208 bar 3017 psi	188 bar 2727 psi

* Minimum operating temperature for Super Duplex stainless steel is -40 °C. Maximum pressure may be lower depending on the design type.

Uncertainties and flow measurement turn-down

The turn down capability from Qₙₒₘ of the flow sensor is driven mainly by its zero point stability. At the very low end of the measuring range the uncertainty (u) is dominated by zero point stability.

• Zero point stability of a standard sensor with general accuracy calibration: 1.5 kg/min (3.31 lbs/min).
• Zero point stability of a premium sensor with high accuracy or focused calibration: 1.35 kg/min (2.98 lbs/min).
• uncertainty = calibration uncertainty, if: flow ≥ (zero point stability / (base uncertainty/100))
• uncertainty = (zero point stability/Q)*100, if: flow < (zero point stability / (base uncertainty/100))

Uncertainties from environmental and process conditions

If sensors are not zeroed at operating conditions, minor additional uncertainties can arise from elevated temperatures and pressures:

• ±0.00125% of maximum flow per °C
• ±0.0001% of maximum flow per bar

Process temperature effect on density:
• Additional uncertainty of ±0.00008 g/cm³ per °C difference from calibration temperature with standard density calibration.
• Additional uncertainty of ±0.000009 g/cm³ per °C difference from calibration temperature with enhanced density calibration.
• This effect can be mitigated by a simple field density adjustment at operating conditions.

Process pressure effect on mass flow:
• The effect of pressure on flow measurement is 0.02% of rate per bar. Compensation is possible by pressure sensor input (analog input or digital write) or manual value entry into the transmitter.

Process pressure effect on density:
• The effect of pressure on density measurement is 0.00003 g/cm³ per bar. Compensation is possible by pressure sensor input (analog input or digital write) or manual value entry into the transmitter.

Applying Premium calibration to higher pressure, special materials and/or non-standard temperature models may show higher zero uncertainties (up to 3 times higher than standard sensor).

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Other wetted materials may be possible for chemical compatibility, lower pressure drop, abrasion allowance or other application specific requirements. Rheonik can provide nearly any material for the wetted parts.