7200 series 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.

7200 Series flow switches have not been submitted for agency approval testing.

Models:

7240 – 1/2″ diameter probe, max length 36″
7260 – 3/4″ diameter probe, max length 60″
7280 – 1″ diameter probe, max length 84″

The Insertion style flow switch includes a sensor probe assembly which is inserted into the process conduit to allow the gas to flow across the sensors. The insertion style thermal mass flow switch probe assemblies may be inserted into any suitable flow section, pipe, duct, etc.

Insertion flow switches are available with 1/2″, 3/4″, or 1″ OD probes and may be installed with pipe fitting connections or user-supplied bored through tube fittings. Tube fittings and ball valve retractor assemblies, with or without a mounting flange, are also available from the factory as options. The tube length must be specified upon ordering. For other probe diameters and lengths, please consult the factory.

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 are provided for verification that the Hi or Lo alarm has been triggered. The standard configuration has 316 Stainless Steel wetted parts (Hastelloy & Monel are also available) for a rugged, cleanable instrument designed for use in applications where corrosion, abrasion, high pressure, or rough handling may be expected.

Thermal mass flow switches 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.