KELLER Series 25Y Front-Flush Pressure Transmitter G1/2

KELLER Series 25Y is a front-flush piezoresistive pressure transmitter for absolute and gauge pressure with 0.25 %FS accuracy. Its G1/2 connection presents a flush metal diaphragm to the medium, so there is no pressure port or dead volume where viscous or contaminated media can collect.

Flush diaphragm with a temperature-compensated Y-line circuit

The datasheet explains how the Y-line achieves its small temperature error: an additional circuit with a temperature sensor divides the temperature range into fields 1.5 K wide and stores TK zero and TK compensation values for each field. Up to 120 fields can represent a 180 K range, and the accuracy is then mainly determined by linearity.

KELLER also points out the extreme ruggedness of the 25Y against electromagnetic fields: the limits of the CE standard are undercut by a factor of up to 10 for conducted and radiated fields. The modular concept uses off-the-shelf sensors with many options for pressure range, port, output and electrical connector.

Key features as printed in the datasheet

• Front-flush G1/2 pressure connection, dead volume change below 0.1 mm3.
• Accuracy 0.25 %FS; typical total error 0.3 %FS (0…50 degC) above 2 bar.
• No internal seals: AISI 316L (1.4404/1.4435) with USIT or Viton O-ring.
• Ranges 0.5…600 bar; Inconel 718 diaphragm above 400 bar (25wY).
• Optional intrinsically safe version, see Series 25Y-Ei datasheet.

Technical specification

Performance and electrical data

Mechanical data

Selection and ordering guide

Overpressure ratings in the range table run from 4 bar for the lowest ranges up to 1100 bar for the highest. Intermediate ranges, for example a barometer range of 0.7…1.2 bar abs., are available on request, as are other pressure and electrical connections.

For the PR (vented) version with a plug, KELLER specifies IP54 and recommends a cable with an integrated reference hose; optional IP68 is available. A mating connector for the Binder or EN 175 301-803-A plug is included in delivery as marked in the datasheet.

Installation and operation notes

A front-flush diaphragm needs a matching flush port or weld-in boss; the KELLER operating instructions for pressure transmitters warn that even small deformations of a flush connection can cause incorrect measurement, so use suitable tools, torque the body on the spanner flats and keep the protection cap on until installation.

The device is not intended for safety functions, and the non-Ei version must not be used in hazardous areas.

Applications in Oman and the GCC

Front-flush transmitters are chosen for viscous, pasty or crystallising media, such as dosing lines, mixers and process lines in the chemical and food sectors. For desalination and water treatment skids the 316L diaphragm should be checked against the chloride and temperature levels of the process.

Compatible accessories and related items

The 25Y-Ei is the intrinsically safe variant, and Series 35X is the digital RS485 front-flush alternative with Modbus RTU. The 35X is also listed on this site.

Frequently asked questions

What does front-flush mean on the 25Y?

The metal diaphragm sits flush with the G1/2 connection face, so there is no pocket where medium can collect.

What accuracy does the 25Y reach?

0.25 %FS, with a total error band of 0.5 %FS maximum at 0…50 degC above 2 bar.

Which signal outputs exist?

4…20 mA two-wire, and 0…10 V, 0…5 V or 0.5…4.5 V three-wire.

Is an intrinsically safe version available?

Yes, KELLER lists Series 25Y-Ei; see its separate datasheet.

Does Seven Star LLC act as a KELLER distributor?

No. Seven Star LLC is an independent supplier in Muscat that sources KELLER products on request.

Documents and quotation

This page carries the official KELLER datasheet for 25Y. Seven Star LLC is an independent supplier in Muscat and sources KELLER products on request; tell us the quantity and delivery point to receive a quotation. Always confirm the order code and technical values in the document first. See more in the product category.