KELLER Series 21Y Compact Pressure Transmitter

Name: KELLER Series 21Y Compact Pressure Transmitter | Seven Star LLC
Brand: KELLER
SKU: 21Y

The KELLER Series 21Y is a compact piezoresistive pressure transmitter from the Swiss manufacturer KELLER Pressure. A 16.6 mm diameter, roughly 60 mm long stainless steel body weighing about 50 g (without cable) houses a sensor covering 0…2.5 to 0…1000 bar, with 4…20 mA, 0…10 V or 0.5…4.5 V output.

A small transmitter for tight installation spaces

KELLER describes the 21Y as having no internal seal and a high insulation voltage of 300 VDC (the datasheet quotes GND-CASE insulation above 10 MOhm at 300 VDC), which makes the fully welded design very resistant to environmental influences. The sensor is an insulated, encapsulated piezoresistive chip, and the signal path is direct analog with a limiting frequency of 1 kHz.

Typical uses named in the datasheet are industrial applications, heat pumps, air-conditioning technology and the food industry. Pressure types are PR (relative, vented), PAA (absolute from vacuum) and PA (absolute from 1 bar), each with its own range table.

Key features as printed in the datasheet

Compensated over -10…80 degC; accuracy 0.5 %FS, total error band 1.0 %FS (0…50 degC) and 1.5 %FS (-10…80 degC).
Fully welded, no internal seal; AISI 316L wetted parts.
Supply 8…32 VDC for 4…20 mA and 0.5…4.5 V, 13…32 VDC for 0…10 V.
Start-up time below 5 ms (0…99 %); overvoltage and reverse-polarity protection to 32 VDC.
Five electrical connection styles including M12 and Packard.

Technical specification

Performance and electrical data

Parameter	Specification
Pressure ranges	0…2.5 to 0…1000 bar (PR, PAA, PA)
Accuracy (BFSL, hysteresis, repeatability)	max. 0.5 %FS
Total error band 0…50 degC / -10…80 degC	max. 1.0 %FS / 1.5 %FS
Compensated temperature range	-10…80 degC
Long-term stability	max. 0.3 %FS per year, reference conditions
Position dependency	max. 1.5 mbar (vertical, connection down)
Output / signal limits	4…20 mA (3.2…22.3 mA); 0…10 V (-1.2…11.2 V); 0.5…4.5 V (0.1…4.9 V)
Supply	8…32 VDC (mA, 0.5…4.5 V); 13…32 VDC (0…10 V)
Current consumption	below 5 mA / below 4 mA as per datasheet
Load	below (U – 8 V)/25 mA (2-wire); above 5 kOhm (3-wire)
Limiting frequency	1 kHz
Start-up time	below 5 ms (0…99 %)

Mechanical and environmental data

Parameter	Specification
Wetted materials	AISI 316L connection and diaphragm; no internal seal; external seal FKM 75 Shore
Oil filling	Silicone oil (others on request)
Pressure connections	G1/4 male, G1/8 male, 7/16-20UNF female or male, 1/4-18NPT
Dimensions / weight	dia 16.6 mm x approx. 60 mm; approx. 50 g without cable
Medium temperature	-20…125 degC, optional -40…125 degC
Ambient temperature	-20…85 degC, optional -40…100 degC; no icing
Ingress protection	IP67 (M12, Packard, cable), IP65 (valve connectors); relative pressure with plug IP54
Vibration / shock	10 g, 10…2000 Hz (IEC 60068-2-6) / 50 g, 11 ms (IEC 60068-2-27)
Pressure cycles	more than 10 million, 0…100 %FS at room temperature
EMC	CE per 2014/30/EU; EN IEC 61326-1, 61326-2-3, 61000-6-1 to 6-4

Selection and ordering guide

The standard range table runs from 2.5 bar (proof 9 bar) through 4, 6, 10, 16, 25, 40, 60, 100, 160, 250, 400, 600 and 1000 bar (proof 1200 bar). The relative PR version also offers -1…range variants up to 25 bar. Choose PR for gauge pressure, PAA when the zero must be vacuum, and PA when zero is 1 bar absolute.

Electrical choices are the 2-wire 4…20 mA, or 3-wire 0…10 V and 0.5…4.5 V outputs, with round plug M12 x 1 (4-pole), Packard Metri-Pack 150 (3-pin), valve connectors Form Ci (9.4 mm) or Form A (18 mm), or a 3.3 mm PUR cable. Confirm the full type code with the datasheet before ordering.

Installation and operation notes

KELLER notes the device is calibrated vertically with the connection facing down, so a different mounting angle shifts the zero by up to the stated position dependency. The enclosed Operating Instructions for pressure transmitters (also published by KELLER for this series) require installation only when the system is unpressurised and de-energised, tightening with a torque wrench on the spanner flats and keeping the protection cap on until installation.

The IP ratings apply only with the matching mating plug fitted. For relative pressure versions with valve connectors, KELLER specifies a cable with integrated capillary so the reference side stays vented.

Applications in Oman and the GCC

The compact body suits refrigerant and chilled-water circuits, heat pumps and compressor skids found in air-conditioning plant, and the food-industry mention in the datasheet points to washdown-style process lines. For Gulf installations the 125 degC medium and 85 degC ambient limits should be compared with plant-room and outdoor panel temperatures; the datasheet lists an optional 100 degC ambient version.

Compatible accessories and related items

KELLER lists Series 21PY, 21C and 23SY as similar products. This site also lists the 21C (ratiometric output) and 23SY (pressure ranges from 0.1 bar), and mating plugs and cables are available as accessories in the KELLER range.

Frequently asked questions

What outputs does the Series 21Y offer?

4…20 mA (2-wire), 0…10 V or 0.5…4.5 V (3-wire), depending on the ordered version.

What pressure range does it cover?

0…2.5 to 0…1000 bar in PR, PAA and PA versions.

What accuracy and error band are stated?

Accuracy up to 0.5 %FS; total error band 1.0 %FS at 0…50 degC and 1.5 %FS at -10…80 degC.

Which wetted materials are used?

AISI 316L for connection and diaphragm, with an FKM external seal and no internal seal.

Is Seven Star LLC a KELLER distributor?

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

Documents and quotation

The official KELLER datasheet for 21Y is hosted on this page for download. Seven Star LLC is an independent supplier in Muscat; send your quantity and delivery location through the quotation form and we will quote this item. Please confirm the exact order code, ratings and approvals against the document before ordering. More related products: product category.

Pressure transmitters and level probes

The KELLER range covers standard and front-flush pressure transmitters, differential and low-pressure transmitters, submersible level probes, digital pressure gauges and data loggers. Many X-line devices combine RS485 Modbus RTU with an analog output, and intrinsically safe or increased-safety versions are offered for hazardous areas.

Frequently Asked Questions