KELLER Series PD-33X Differential Pressure Transmitter

KELLER Series PD-33X is a piezoresistive differential pressure transmitter with excellent accuracy, 0.05 %FS, for differential ranges from 0…0.3 to 0…30 bar at line pressures up to 600 bar. It uses a classic wet-wet encapsulated chip, so both pressure ports can see liquid or gas media.

Wet-wet differential measurement with high line pressure

The datasheet lists filter monitoring, flow-rate measurement, leakage measurement, laboratory use and industrial applications. Line-pressure dependency is below 0.005 %FS per bar for ranges of 3 bar and above, and below 0.15 mbar per bar for ranges under 3 bar.

Two body versions are given by line pressure: up to 200 bar (about 500 g) or up to 600 bar (about 650 g). The device offers an RS485 interface with Modbus RTU, combinable with a rangeable analog output, and the smallest scalable analog range is 0.1 bar.

Key features as printed in the datasheet

• Differential ranges 0…0.3 to 0…30 bar; line pressure up to 600 bar.
• Accuracy 0.05 %FS; total error band 0.05 %FS (10…40 degC), 0.1 %FS (-10…80 degC).
• Modbus RTU and KELLER bus on RS485; analog interface rangeable by software.
• Pressure range reserve of 10 %; temperature output with 0.01 degC resolution.
• Ports G1/4 female or 1/4-18NPT female, 316L.

Technical specification

Performance and electrical data

Mechanical and environmental data

Selection and ordering guide

Pick the differential range for the expected pressure drop across the filter or element, and the body for the highest static line pressure: 200 bar or 600 bar. The datasheet notes that intermediate analog ranges can be scaled from the standard ranges at no extra charge, down to a 0.1 bar span.

Specify the compensated temperature band (10…40 degC or -10…80 degC) as an ordering option and the electrical connector. For ranges below 1 bar all specifications refer to a full-range signal of 1 bar.

Installation and operation notes

The transmitter is calibrated with the pressure connections horizontal, so install it in that orientation to hold the 3 mbar position tolerance. Pressurise both ports together to avoid overloading the diaphragm in one direction, and respect the stated proof pressures.

Digital configuration follows the other X-line devices with the CCS30 software and an RS485-USB converter. When an error occurs the device returns NaN, and outside the 10 % reserve it returns plus or minus Inf, which a PLC should handle.

Applications in Oman and the GCC

Differential pressure across strainers, cartridge filters and coalescers is a staple of oil and gas, power-plant lube systems and water treatment. The 0.05 %FS accuracy also suits orifice and venturi flow measurement and leak testing, where line pressure is high.

Compatible accessories and related items

The single-port 33X is also listed on this site. KELLER also lists PD-23X, PRD-33X and PD-39X differential versions, and PD-33X-Ei for intrinsically safe loops. Confirm the line-pressure version, differential range, compensated temperature band and plug type in the datasheet before ordering.

Frequently asked questions

What does wet-wet mean?

Both pressure ports act on the sensor through separating diaphragms, so liquids or gases can be present on both sides.

What line pressures are available?

Versions for up to 200 bar and up to 600 bar line pressure.

How accurate is the PD-33X?

0.05 %FS at room temperature and 0.1 %FS total error band over -10…80 degC.

Which ports does it have?

G1/4 female and 1/4-18NPT female.

Does Seven Star LLC act as a KELLER distributor?

No, we are an independent supplier in Muscat and supply KELLER items on request rather than acting as a KELLER channel partner.

Documents and quotation

Need PD-33X? The KELLER datasheet is attached to this listing. Seven Star LLC (independent supplier, Muscat) can quote the item and arrange supply on request; list quantity and site location in your enquiry. Verify the code, dimensions and approvals in the document before ordering. Other products are in the category page.