JUMO MAERA F27 Ceramic Level Probe with PTFE or Steel Case

A ceramic-cell level probe for acids, lyes and electroplating baths

The JUMO MAERA F27 (type 404391) is a hydrostatic level probe whose capacitive ceramic cell (99.9 % Al2O3) tolerates aggressive media better than a metal diaphragm. It starts at 50 mbar, so shallow tanks of about 0.5 m water column can be monitored, and goes up to 1.6 bar (about 16 mWS). Linearity is 0.2 % of span. It can be used indoors and outdoors; the stainless-steel version has integrated overvoltage protection (1 kA rated leakage current) for lightning events in surrounding water, a PTFE-cased version handles acids and lyes, and a Pt100 can be added to record medium temperature for density compensation. The datasheet lists water and sewage management, aggressive media and electroplating baths as applications. The cell is vented through the cable, so atmospheric pressure changes are compensated automatically.

Technical specifications

Ordering the F27

The code is 404391/ basic type – range – output – process connection – cable type – cable length / extra code, with the datasheet example 404391/000-452-405-659-15-010/000, a steel-case 0 to 0.4 bar probe with 4 to 20 mA, open connection at the bottom, black PE-LD cable and 10 m of cable. Basic type 007 adds the Pt100 and is only available with 4 to 20 mA and the closed or open bottom connections. The PTFE case (022) is only available with the G 1 inside connection and cannot take the cutting-ring fitting. Integrated overvoltage protection works only with the 4 to 20 mA output. Accessories include the terminal box with pressure-compensation element (00061206), a cable clamp (00753260), a sealing screw (00333329) and a pressure-compensation filter. Use FEP cable for aggressive media and keep the compensation hose unkinked.

Where the ceramic cell earns its place

Metal-diaphragm probes such as the MAERA S25 are the better general choice for clean water, while the F27 is the one to pick for acid dosing tanks, pickling and plating baths, caustic storage and wastewater with chemicals. The PTFE case limits medium temperature to 0 to 40 °C, so verify the bath temperature, and always check chemical compatibility of ceramic, PTFE or steel and seals with the medium. In coastal plants the integrated surge protection helps for outdoor wells and sumps exposed to lightning. For seawater use the titanium MAERA S29 SW, and browse the level instrumentation category for float switches and transmitters.

For a quotation, state the level range in millibar or metres of water column, the output signal, and whether the medium is clean water, sludge or an aggressive liquid, which decides between the steel case and the PTFE case. The steel version is 41 mm in diameter and the PTFE version 50 mm. Specify the cable material and length, the sealing material, and the closed or open bottom. The sensor is submersible to 16 m and the cable includes a hose for pressure compensation, so the cable end must be kept dry and ventilated. Overvoltage protection is built into the steel version for outdoor tanks and wells.

Use the lower ranges for tank level in millimetres, where 100 mbar corresponds to about one metre of water. The ceramic sensor tolerates dirty water, but the cable end should always be kept above the liquid and sealed against humidity, and the probe should hang freely away from inlets and agitators.

Documents and quotation

The hosted document is JUMO data sheet 404391 (10 pages, English, V5.00). Confirm the range, case material, cable and approvals for your medium before ordering. Seven Star LLC is an independent supplier in Muscat; send the code, medium and tank depth for a quotation.