mini flowmeter
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Hoffer Mini-Flowmeter Engineering Guide MF SERIES FOR LOW FLOW APPLICATIONS New devices with low flow measurement capability are increasingly in demand by industrial and laboratory users as requirements for accurate low flow measurement devices proliferate. The Hoffer MF Series has been developed to meet the need for a low flow measurement device for service on clean, low and moderate viscosity liquids, and for gas measurement applications. The MF Series is a family of low flow rate measurement devices based on a pelton wheel like rotor. The measured fluid is directed tangentially thru a velocity nozzle against the pelton rotor causing it to rotate. The motion of the rotor is sensed by the pickup coil and converted to a pulsing output signal where the frequency is related to the flow rate, and the accumulated pulses are related to the total volume passing thru the flowmeter. Materials Selection and Construction Selection of the materials of construction is usually dictated by the requirements of performance, durability, media compatibility, availability, and cost considerations. The materials of construction for the MF Series are intended to provide a standard flowmeter configuration which will suit the requirements of a broad base of industrial users. Our applications group can assist you in the selection of options that will provide the construction which offers the optimum combination of useful range, corrosion resistance and operating life for a particular application. Bearing Selection Bearings are chosen based on media compatibility, desired turndown range, service life, serviceability, cost, and accuracy considerations. Several bearing types are available including self-lubricating, ceramic hybrid ball bearings and sleeve constructions in tungsten carbide and carbon composites. The side access port permits for rapid inspection and servicing of the flowmeter internals including the bearings. When selecting among several chemically compatible bearings, the ball bearing design offers the highest accuracy and widest usable range and may be considered the standard. It is required for gas measurement applications. Field bearing replacement may be performed without a significant shift in the original calibration. Tungsten carbide offers the most durable bearing material in service conditions where it is compatible, and will offer the longest life in rugged industrial liquid service. Hard carbon composite bearings offer properties which are nearly chemically inert to many corrosive fluids and are utilized for this reason in demanding applications.

Flowmeter Pickup Selection The flowmeter pickup coil senses the motion of the rotor and converts it to a pulsing electrical signal which is of a discrete digital nature. Two basic pickup types are offered for use with the MF Series which will satisfy standard electrical interface requirements for turbine flowmeters. The standard flowmeter pickup is a low drag magnetic type whose selfgenerating output signal voltage is approximately sinusoidal. The amplitude of the output signal is a function of flow rate, with a minimum signal strength which is greater than 30 mVp-p. The standard maximum...

Figure 4 Standard Specifications Flow Rate Capability with Ball Bearings End Fitting Type: 1/2" MS-33656-8 (Std. others available upon request) Physical: Operating Pressure: 1000 PSI (standard) 6000 PSI (optional) Flowmeter Size Linear Range MIN Repeatable MAX Repeatable MIN MAX GPM CC/M GPM CC/M GPM CC/M .015 .017 57 65 .049 .120 185 450 .007 .0085 26.5 32.0 .065 .150 250 575 MF40 .020 75 .150 575 .010 38.0 .200 750 MF50 .023 85 .200 750 .013 50.0 .350 1325 MF60 Materials: Housing: 316 Stainless Steel Bearing: Ceramic Hybrid Ball Bearings (self-lubricating) Tungsten Carbide Sleeve...

PSID=(Cpse)¼ X (SpGr)3/4 x PSID(H2O) where: Cpse is viscosity in centipoise SpGr is the specific gravity PSID(H2O) is pressure drop from Figure 5 Specifications for Liquid Applications Output Frequency Range: 50 to 1000 Hz (3333 Hz Maximum) Linearity: ±1.0% reading (over 10:1 range) Linear Range: 10:1 turndown with magnetic pickups and ball bearings Usable Flow Range: 25:1 with ball bearings Repeatability: ±0.1% typ. (±0.25% worst case) Reference conditions: 1 cstk. test fluid at 70° F Viscosity Effects An ideal flowmeter may be defined as one in which the output is solely a function of the...