Eldridge Products, Inc. - EPI Flow Averaging Tubes
Contact Us
Product Information
Series 8000MP Master-Touch™ Flowmeters
Series 8000MPNH Master-Touch™ Flowmeters
Master-Touch™ Flow Averaging Tubes (FAT™)
Series 9000MP Multipoint Flowmeters
Series 7000–7200 Flow Switches
EPICommunicator (EPICom) Flowmeter Software
LightWIRE Infrared Flow Meter Communications
Technical Information
Master-Touch Solutions
Domestic Sales
International Sales
Request a Quote


Eldridge Products, Inc.’s innovative new Flow Averaging Tubes (FAT™) provide accurate flow measurement in large pipes and ducts without the expense and complexity of traditional multipoint systems, offering a cost-effective solution for Heating, Ventilation, and Air Conditioning (HVAC) and Variable Air Volume (VAV) applications. They also provide accurate, repeatable readings in applications with very limited upstream straight run.

The Master-Touch FAT™ probes utilize a flow averaging tube to give a stable flow signal in applications where the flow profile is less than ideal, such as downstream of a bend, valve, tee or obstruction. The flow averaging tube has a number of large diameter (0.125”) inlet ports along the length of the upstream impact surface. The impact pressure at each inlet port is averaged inside the tube to create the axial flow through the tube and across our flow sensor. The gas flow then passes back into the main flow stream through the gas return ports located near the flow sensing elements.

Anomalies in the actual flow profile or installations in non-circular ducts may require a C-Factor adjustment for the best accuracy. The velocity impact pressure follows a square root function. Therefore, the average velocity pressure in the FAT™ probe may vary slightly from the average of the velocities at each inlet port. The Master-Touch electronics easily accommodate the C-Factor adjustment.

The Master-Touch MP Series FAT™ probes are now approved for use in hazardous area locations:


CSA/CUS – For use in hazardous area locations; Class I Group B,C,D; Class II Group E,F,G; CLASS III; Encl Type 4X; Class I Zone I; AEx d IIB+H2 IP66; Ex d IIB+H2 IP66; T2 or T3 or T4 as marked; Ta = 0°C TO 50°C

ATEX – Ta = 0°C TO 50°C; IP66; Ex d IIB+H2 T4 Gb/EX t IIIC T135°C Db or; Ex d IIB+H2 T3 Gb/EX t IIIC T200°C Db or; Ex d IIB+H2 T2 Gb/EX t IIIC T300°C Db; SIRA 12ATEX1302
IECEx – For use in hazardous area locations; T2 or T3 or T4 as marked; Ta = 0°C to 50°C;; Ex d IIB+H2 T2...T4 Gb IP66; Ex tD A21 IP66 T135°C...T300°C; IECEx CSA 11.0014
KOSHA – For use in hazardous area locations; T2 or T3 or T4 as marked; Ta = 0°C TO 50°C; Ex d IIB+H2 T2...T4 Gb IP66; Ex tD A21 IP66 T135°C...T300°C

The remote enclosure is certified for use in Ordinary (Non-Hazardous) area locations:
Type 4X, IP66

Insertion Style

Mounting insertion style tubes in pipes or ducts typically uses tube to pipe compression fittings or flanges (as shown below). "Hot tap" options with ball valve retractor assemblies are also available. Multiple tubes can be used with a Model 9601MP System Control Panel for a grand-averaged output.

Inline Style

By itself, EPI’s Flow Averaging Tube technology significantly reduces the traditional requirements for straight, unobstructed upstream piping. Depending upon the piping configuration, the traditionally required upstream straight run can be 10, 20, even 50 diameters. By measuring the cumulative flow velocities across one or more inside diameters, the Flow Averaging Tubes are far more tolerant of flow profile problems than other instrument technologies. This allows the required straight run to be greatly reduced. And, when coupled with our Flow Straightening Plates, the upstream requirement can be reduced to as little as three diameters.


MP Series FAT™ flowmeters are approved for use in hazardous locations. Series 9100MP-9200MP instruments have an explosion-proof flow transmitter mounted at the point of measurement with the signal processor electronics remotely mounted in a separate, general purpose enclosure. An explosion-proof enclosure for the remote electronics is available as an option. The Series 9700MP-9800MP instruments have all electronics mounted at the point of measurement in an explosion-proof enclosure.

MPNH Series FAT™ flowmeters are designed for installation in non-hazardous environments. They feature 5” x 5” x 4” ABS plastic enclosures. Series 9100MPNH-9200MPNH instruments have the flow transmitter mounted at the point of measurement with the signal processor electronics remotely mounted in a separate enclosure. Series 9800MPNH instruments have integral electronics mounted at the point of measurement.

The connections for input power and output signals for the Model 9200MP and Model 9200MPNH are located in the remote electronics. This configuration uses only a two-wire connection between the flow transmitter and the signal processor. All input and output connections for the Model 9800MP and 9800MPNH are available in the integral electronics enclosure.

As with all Master-Touch thermal mass flowmeters, you get a powerful set of features that includes:

  • Tracking of overall gas consumption over a turndown ratio of at least 100:1 with an accuracy of ±[1.0% of Reading +(0.5% + 0.05%/°C of Full Scale)], and repeatability of ±0.2% Full Scale;
  • Extensive diagnostics including time and date stamping of maximum and minimum flow rates;
  • User-selectable high or low biasing to optimize long term tracking against supplier metering;
    A 2 line, 16 character display for rate, total, and relay status;
  • Up to four independent metering ranges, and the ability to switch between the ranges without interrupting your production process; and
  • A wide variety of user-selectable engineering units that dynamically convert the flow rate and elapsed total to the new units.

You can control all of these features with the four button touch keypad or via RS232 and RS485 I/O communications using EPICommunicator software. Please see our pages for the MP Series thermal mass flow meters and EPICommunicator for a full description of these features.

MASTER-TOUCH™ Flow Averaging Tubes

Click on a picture below for larger, printable image. For best printing, select Landscape in Page Setup menu. Click your browser's "Back" button to return to this page.

 Click on the links below for .pdf files:


The specifications presented are subject to change without notice. EPI cannot guarantee the applicability or suitability of our products in all situations, since it is impossible to anticipate or control every condition under which our products and specifications may be used.


Eldridge Products, Inc. (EPI) warrants its products to be free from defects in materials and workmanship for one year from the date of factory shipment. If there is a defect, the purchaser must notify EPI of the defect within the warranty period. Upon receipt of the defective product, EPI will either repair or replace the defective product or refund the purchase price at its sole option. EPI MAKES NO OTHER WARRANTY, EXPRESS OR IMPLIED, AS TO THE PRODUCTS. EPI MAKES NO WARRANTY THAT THE GOODS SOLD TO ANY PURCHASER ARE FIT FOR ANY PARTICULAR PURPOSE. FURTHERMORE, EPI MAKES NO WARRANTY OF MERCHANTABILITY WITH RESPECT TO ANY PRODUCTS SOLD TO ANY PURCHASERS. There are no other warranties that extend beyond the description on any brochure or price quote.

U.S. Patent No. 6,883,389
Other U.S. & foreign patents pending.


© Copyright 2014 by Eldridge Products, Inc. All Rights Reserved