800 HPN products offer a feature set designed for a variety of Ultra High Purity and High Purity applications including Semiconductor & Displays, Pharmaceutical, Biotechnology, Food & Beverage, and other processes that require a clean hygienic flow meter. The product includes 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 a VCR style for easy removal and cleaning and 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.

800 Series flow meters are approved for use in non-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 6″ pipe. The internal wetted surfaces may be electro-polished to either a 10 Ra or 25 Ra surface finish. Inlet flow conditioning plates are optionally available on flow sections from ¾” to 6”. Mounting is via butt weld ends. Optional end configurations include – Tri-Clamp style ends, or male VCR style ends for ½”, ¾” or 1” tubes.

Integral style thermal mass flow meters have all the electrical components and connections located within one enclosure. This enclosure is rated for non-hazardous environments. The enclosure is mounted directly to the inline flow section assembly at the point of measurement. The enclosure includes all the electrical connections as well as the linearizing electronics and the display assembly.

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.