The Series 7000 is a thermal mass flow switch that detects the presence of the flow, at a predetermined set point, sends alerts, and performs designated actions. Designed with inline installation type, these thermal mass flow switches are available in sizes from 1/4″ pipe through 4″ pipe and are provided with threaded male NPT ends as the standard mounting style. While the Series 7000 is designed with an explosion-proof enclosure for hazardous locations, the model has still not been submitted for agency approval testing.
To provide accurate measurements and detection, the Series 7000 uses proprietary temperature compensation techniques with a sensor assembly that utilizes two RTD (Resistance Temperature Detector) sensing elements. Our high-stability sensors are made of reference-grade platinum, ceramic, glass, and stainless steel, while the final assembly is slipped into a stainless-steel sheath for corrosion and abrasion resistance.
The enclosure for the Series 7000 flow switch offers a rating for use in hazardous locations with T2, T3, and T4 approvals and it is available in domestic and international markets. The diecast aluminum, NEMA Type 4X watertight enclosure is both flame and explosion proof and features a corrosion resistant finish.
The 7000 series flow switch 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 constructed of reference grade platinum, ceramic, glass, and stainless steel. Two platinum resistance sensors are built up upon the ceramic substrate and then receive a thin glass coating. The assembly then slips 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. It also maintains a reference resistance on one side of a bridge circuit. The second sensor undergoes self-heating to a constant temperature above that of the gas stream. The temperature sensor and bridge circuitry controls the heating process. The bridge maintains the overheat temperature and counterbalances the temperature effects through proprietary temperature compensation techniques.
The inline style thermal mass flow switch includes the flow sensing element, temperature sensing element, bridge amplifier/signal output board, transmitter enclosure, and flow section. The flow section matches the user’s flow conduit and plumbs directly in the flow line. The sensing elements mount directly in the flow section for exposure to the process flow.
Inline flow switches are available in sizes from 1/4″ pipe through 4″ pipe and offer threaded male NPT ends as the standard mounting style. Optional end mounting styles are available, such as tube ends, tube end fittings, butt weld ends, flanged end configurations, etc. Pipe sizes more than 4″ typically require insertion style thermal mass flow switches.
All of EPI’s flow switches have two single-pole, double-throw relays for Hi/Hi, Lo/Lo, and Hi/Lo capability. The contact closure is 5 amps @ 24 VDC and 115 VAC. Two LEDs provide verification when the Hi or Lo alarm triggers. The standard configuration has 316 Stainless Steel wetted parts (Hastelloy & Monel are also available). This design provides a rugged, cleanable instrument that’s suitable for use in applications where corrosion, abrasion, high pressure, or rough handling may occur.
Thermal mass flow switches use the principle of convective heat transfer to directly measure mass flow. Our proprietary thermal mass flow sensors use two ratiometric, reference-grade platinum Resistance Temperature Detectors (RTDs). The platinum sensing element wire is within a 316 Stainless Steel sheath or, if necessary, a Hastelloy C sheath.
Smart sensor technology operates the microcontroller which preferentially heats one RTD. Then, the other RTD acts as the temperature reference. The process gas flow dissipates heat from the first RTD, thus causing an increase in the power necessary to maintain a balance between the RTDs. This increase directly relates to the gas molecular rate of flow. Our sensors also offer temperature compensation for a wide process gas temperature range. They are also insensitive to pressure changes, so the output signal is a true mass flow rate signal.
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