Product Description

Master-Touch™ products include a rugged, cleanable, thermal mass flow sensor. These units consist of a sensor assembly which utilizes two RTD (Resistance Temperature Detector) sensing elements. The sensors are constructed of reference grade platinum, ceramic, glass, and stainless steel. Two platinum resistance sensors are built up upon the ceramic substrate and then given a thin glass coating. The assembly is then slipped into a stainless-steel sheath for corrosion and abrasion resistance. The sensor assembly is large, rugged, and relatively insensitive to dirt buildup. During operation, the temperature sensor constantly measures the ambient temperature of the gas and maintains a reference resistance on one side of a bridge circuit. The second sensor is forced through self-heating to a constant temperature above that of the gas stream and is controlled by the temperature sensor and bridge circuitry. Our bridge maintains the overheat temperature and counterbalances the temperature effects through our proprietary temperature compensation techniques.

9000-9100 Series flow meters are approved for use in hazardous locations (see specifications).

Inline style thermal mass flow meters include a flow section that is usually specified to match the user’s flow conduit and is then plumbed directly into the process line. This design has the sensing elements mounted directly in the flow section for exposure to the process gas. Our inline style thermal mass flow meters are available in sizes from 1/4″ pipe through 4″ pipe or tube and are provided with a variety of options such as MNPT ends, tube end fittings, butt weld ends, flanged end configurations, etc. as required. Pipe sizes more than 4″ typically require insertion style thermal mass flow meters.

Remote style thermal mass flow meters utilize two enclosures. One enclosure is mounted at the point of measurement on the probe assembly. This enclosure is rated for hazardous environments. The second (remote) enclosure is usually placed in a readily accessible location rated for non-hazardous conditions. (Contact the factory for information concerning remote explosion-proof enclosure). The remote enclosure includes all the electrical connections as well as the linearizing electronics and the display/keypad assembly. A 5-conductor shielded cable is required to carry the flow signal between the two enclosures.

Thermal mass flow meters use the principle of convective heat transfer to directly measure mass flow. EPI’s proprietary thermal mass flow sensors use two ratiometrically-matched, reference-grade platinum Resistance Temperature Detectors (RTDs). The platinum sensing element wire is encapsulated in a 316 Stainless Steel sheath or, if specified, a Hastelloy C sheath. Our microcontroller operated smart sensor technology preferentially heats one RTD; the other RTD acts as the temperature reference. The process gas flow dissipates heat from the first RTD, causing an increase in the power required to maintain a balance between the RTDs. This increase is directly related to the gas molecular rate of flow. Our sensors are temperature compensated for a wide process gas temperature range and insensitive to pressure changes, so the output signal is a true mass flow rate signal.