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Chaltron Systems, Inc. is proud to represent ELDRIDGE PRODUCTS, INC.

EPI provides Thermal Dispersion mass flow metering solutions for all branches of industry.  All instruments are assembled, calibrated and tested in the Marina, CA facility.

For over 30 years, EPI™ has specialized in manufacturing accurate,
economical and reliable thermal mass flow meters and other flow related products that are proudly made in the USA.  These products include single point measuring systems, multi-point measuring systems, flow averaging tubes, and high temperature measurements up to 977°F / 525°C.

EPI™ flow meters are immersion type inferential mass flow meters utilizing constant temperature thermal dispersion sensor technology. The rate of heat absorbed from the sensor by the flowing gas molecules contacting the sensor is proportional to the gas mass velocity. Mass flow rate is this mass velocity passing through a fixed area. By math, mass velocity x area = mass flow. Sensor construction consists of two matched, reference-grade platinum Resistance Temperature Detectors (RTDs) sheathed in rugged thin wall 316 stainless steel thermo wells. The only materials exposed to the process gas stream are 316 SS (or optional Hastelloy C276).

The sensors’ RTDs are temperature corrective and operate at a constant power differential. The flow sensor is heated, while the second sensor acts as a temperature reference, taking on the temperature of the flowing process gas. The flow meter’s digital electronics maintain the balance the two the flow sensing elements. Within a wide range, the sensor has pressure corrective properties since the molecular density will increase or decrease proportionally with pressure and so the sensor is insensitive to typical process pressure changes. As a result, no external temperature or pressure corrections are required to achieve accurate flow measurements.


As heat is dispersed from the flow sensor to the moving gas stream during the NIST-traceable calibration process, we closely measure both the gas flow and the amount of power required to maintain the correct temperature differential between the heated and unheated sensors. The power required to maintain this balance — the flow signal — is a non-linear function of flow rate. This flow signal is linearized by the unique coefficients stored in the flow meter’s microprocessor, and the flow meter provides a true mass flow output.

We do our flow calibrations using a variety of gases in order to match our customers needs. Any gas that is not specifically on our list can in most cases be substituted with another gas or mixture of gases.

Gases on our list include, Air, Argon, Ethylene, Ethane, Propane, Methane, Carbon Dioxide, Helium, Nitrogen. Methane is use as a substitute gas for Natural Gas. Air is used as a substitute gas for Oxygen. Other mixes determined based on customer gas composition.

Eldridge Ohio Kentucky


MP Series

In many industries the need for monitoring gas Flow involves hazardous gases, potentially dangerous operating environments or simply a desire for a rugged, industrial ~ strength configuration.

EPI developed MP. The to address those issues. The Master Touch MP Flow Meters are approved for use in hazardous area locations.

  • Certified to CE requirements

  • Certified to USA, cUS requirements

  • Certified to Canadian CSA requirements

  • Certified to European ATEX requirements

  • Certified to International IECEx requirements

  • Certified to Korean KOSHA requirements.

All of our Master-Touch™ Flow Meters have 0–5 VDC & 4–20mA output signals proportional to the gas mass flow rate as standard features.  Also included are two 1 Amp @ 30 VDC Relays fully programmable that may be set to trip on various events or alarm conditions. Typically set to High & Low trip values.  RS 485 Modbus RTU & RS232 communications are embedded in the firmware. BACnet, HART, or Profibus DP communications are available options. Rugged 316L SS construction, Optional 2-line, 16 character back-lit LCD display Ex, NEMA 4X (IP66).

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MPNH Series

In many applications the need for monitoring gas Flow does not involve a hazardous area location rating or other potentially dangerous operating conditions.


These applications can include many water and wastewater  treatment, HVAC, general use of compressed air, and many other applications using nitrogen, argon, hydrocarbons, etc. EPI developed MPNH for ordinary locations, Type 4x, IP66.  Available as Integral or Remote versions.

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Flow Averaging Tube (FAT) Series

The patented Master-Touch Flow Averaging Tube (FAT™) Flow Meters are well suited to most applications with limited available straight run.

This innovative design utilizes technology 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 probe has a number of large diameter inlet ports along the length of the upstream impact surface. The 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 returns to the main flow stream through the ports located near the sensing elements. Anomalies in the actual flow profile or installations in non-circular ducts may still some require minor adjustment to achieve the best accuracy. The Inline style FAT include a pair of flow conditioning plates.


In most installations, the upstream straight run can be as little as three diameters.  Available as MP for Hazardous locations or MPNH for general purpose locations.

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Multi-Point Systems

Eldridge Products’ Series 9000MP Multipoint Systems are designed to
measure gas Flows where two or more sensing points are required due to large cross-sectional areas, such as large air intake ducts or exhaust and flue stacks. Our multipoint systems are installed throughout the world, providing our customers with years of steady, reliable service. 


These systems can have up to 5 sensors on each probe. Our System Control Panel (SCP) will average all sensors from all probes. Many probes can be connected to one SCP. Coupled with our new Air Purge System (APS), the Series 9600MP Multipoint Systems are now well-suited to an even greater variety of industrial applications.


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High Temperature MPHT Series

The Master-Touch Series MPHT Series Flow Meters are for use in hazardous area locations (Flame Proof locations) with the ability to perform at high temperatures, up to 977°F / 525°C.​  The meters can have integral or remote electronics.

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High Purity HP Series

Our Series 800HPX includes 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.  Available as 800HPX Explosion Proof Deisgn or 800HPN General Purpose deisgn.

The Series features a VCR style sensor for easy removal and cleaning. 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.



400/440 & 500/540 Series

ValuMass Series 400 & 500 have offered a lower cost option for many flow applications while still providing the high value associated with all EPI’s flow measurement instrumentation.

  • Fully programmable relay

  • Rugged 316L SS construction

  • Optional 2-line, 16 character backlit LCD display

  • NEMA 4X (IP66)

  • Robust feature set: 0-5 VDC or 10 VDC, 4-20 mA, Event Relay, RS485 Modbus RTU and 0-1 kHz outputs.

ValuMass™ inline and insertion flow meters accommodate virtually all installation requirements.  ValuMass™ flow meters accept 24VDC, 115VAC or 230VAC input power as specified at the time of purchase.


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