7MF4033-1BA10-2AC7-Z Siemens Absolute Pressure Transmitter SITRANS P DS III P410 HART 4-20

Siemens 7MF4033-1BA10-2AC7-Z | SITRANS P DS III Gauge Pressure Transmitter — HART / 4–20mA, Span 0.01–1 bar, Overload 6 bar, Stainless Steel, 1/2-14 NPT, SIL 2

Overview

The Siemens 7MF4033-1BA10-2AC7-Z is a SITRANS P DS III gauge pressure transmitter — the practical core of field-level pressure measurement in process plants worldwide.

It sits at a pipe or vessel connection, senses the applied pressure through its stainless steel measuring diaphragm, converts that pressure to a proportional 4–20mA current, and sends both the analog current and HART digital data to the control room over a standard two-wire loop. 

What comes back from the control room is the supply voltage that powers the transmitter — the two wires carry both power and signal in both directions, which is what makes HART's 4–20mA two-wire architecture so persistent in process industries decades after its introduction.

The DS III designation places this transmitter in the Siemens Digital Series III generation — a platform distinguished by its microcontroller-based signal processing, HART communication capability, extensive on-board diagnostics, and SIL 2 certification. Where earlier pressure transmitters relied on analog electronics, the DS III series digitises the sensor output and corrects for temperature and non-linearity in firmware, achieving significantly better accuracy and long-term stability than analog compensation techniques.

The result is a transmitter that maintains its calibration over wide ambient temperature variations and stays accurate through years of continuous operation without recalibration.

The measuring span of 0.01 to 1 bar g covers the low-pressure range with precision — a span from 10 mbar to 1 bar that serves compressed air at low pressures, water supply at modest heads, low-pressure gas distribution, and process vessels where pressure differentials are small.

The 6-bar overload limit provides a safety factor of 6:1 against the top of the measuring range, protecting the measuring cell against pressure transients that occur during valve operation, pump start-up, and line purging.

Key Specifications

HART Communication — What It Adds to the 4–20mA Loop

The 4–20mA analog signal carries the primary measurement value — 4mA corresponding to the lower range value (0.01 bar) and 20mA to the upper range value (1 bar). This signal reaches the control system's analog input card and is displayed as a process value.

The HART digital signal, superimposed on the same two-wire loop as a frequency-shift keyed (FSK) signal at 1200 baud, carries a parallel channel of information that the analog signal cannot convey.

Over HART, the transmitter makes available its measured process value in engineering units at full HART resolution (higher than the analog signal's 16-bit equivalent), device status information (including whether the measuring cell or electronics have detected an internal fault), configuration data (tag name, unit, range values), and diagnostic variables. A HART-capable handheld communicator or a HART modem connected to the loop can read all this data while the transmitter continues its normal analog output — no loop interruption, no signal distortion.

For the SITRANS P DS III, HART communication enables remote configuration of the transmitter's range — changing the lower and upper range values without physically accessing the transmitter.

An instrument technician at the control room or maintenance workstation can rescale the transmitter for a new process condition, simulate an output for loop test, or run the transmitter's built-in diagnostic functions over HART without visiting the field device.

Stainless Steel Measuring System — Corrosion Resistance and Process Compatibility

The stainless steel seal diaphragm and measuring cell are the elements that physically contact the process fluid. Stainless steel — typically 316L in process instrumentation applications — provides corrosion resistance to a wide range of process fluids: water (including treated and demineralised water), compressed air, steam, non-aggressive gases, hydraulic oil, and mild chemicals.

The silicone oil fill transmits the process pressure from the seal diaphragm across a small gap to the capacitive measuring cell without direct contact between the process fluid and the cell's sensitive electronics.

This oil-filled construction isolates the measuring cell from the process chemistry — the measuring cell senses pressure through the oil fill and never contacts the process fluid directly. Process compatibility therefore depends on the seal diaphragm material, not on the measuring cell.

For corrosive media that attack 316L stainless steel — strong acids, chlorine compounds, seawater at elevated temperatures — Hastelloy C-276 diaphragms are available in other SITRANS P DS III order configurations.

SIL 2 Capability — Safety-Integrated Measurement

The SITRANS P DS III series carries SIL 2 certification per IEC 61508 and IEC 61511 — the international standards for functional safety in process plants.

SIL 2 capability means the transmitter has been assessed and qualified for use in Safety Instrumented Functions (SIF) where the required Safety Integrity Level is 2, covering applications where a dangerous failure of the measurement function could contribute to a process hazard.

SIL 2 qualification requires demonstration of the transmitter's probability of dangerous failure on demand (PFDavg), its architectural constraints (hardware fault tolerance), and the functional safety assessment of its design.

The DS III series achieves this through its diagnostic coverage — the built-in self-diagnostics that continuously test the measuring cell, electronics, and output circuit during normal operation.

Any detected fault triggers the defined safe state output (typically driving the 4–20mA output to 3.6mA or 21.6mA, outside the normal 4–20mA range, to signal a fault to the safety logic controller).

FAQ

Q1: The transmitter has a measuring span of 0.01–1 bar. Does this mean the zero of the range is always at 0.01 bar, or can the span be adjusted within this range?

The 0.01–1 bar figure defines the configurable span limits — not a fixed zero-to-span mapping.

The lower range value (LRV) can be set anywhere from 0.01 bar to within the span, and the upper range value (URV) can be set from the LRV up to 1 bar. For example, the transmitter could be configured for 0.05–0.5 bar, 0–0.8 bar, or any other range within the 0.01–1 bar limits.

The 4mA output corresponds to the configured LRV and 20mA to the configured URV.

This makes one transmitter serve multiple applications by reconfiguring the range in the field.

Q2: What does the -Z suffix in the order number indicate?

The -Z suffix signifies that the transmitter includes one or more customer-specific options or configurations beyond the standard base specification.

For the 7MF4033-1BA10-2AC7-Z, the -Z indicates that specific supplementary codes have been selected from the SITRANS P DS III option list — these may include material certificates, special calibration documentation, modified settings, or other application-specific features.

The specific options selected with -Z are identified in the original order documentation and may include certificates, test reports, or specific output configurations not visible in the base order number.

Q3: Can the transmitter be used in wet or outdoor environments — what is its IP protection rating?

The standard 7MF4033 series with die-cast aluminium housing and M20×1.5 cable gland achieves IP65/IP67 ingress protection depending on the specific variant and seal condition.

The window in the housing cover (indicated by the -2AC7 configuration) allows the digital display to be read from outside without opening the housing, while the housing itself remains sealed.

For submersion or high-pressure wash-down applications, the specific IP rating and housing material should be confirmed from the transmitter datasheet.

Q4: The product is listed as discontinued, with the P320/P420 as successors. Are they direct drop-in replacements?

The SITRANS P320 and P420 are functional successors — they provide equivalent gauge pressure measurement with HART output and improved specifications. However, they are not mechanical drop-in replacements.

The P320/P420 series uses an updated housing form factor, different cable entry dimensions, and a different pushbutton layout than the DS III.

The process connection (1/2-14 NPT) is compatible, so the process piping remains unchanged, but the junction box, cable routing, and mounting bracket may require modification. 

Configuration also requires using the new device description files in the HART tool or configuration software.

Q5: How is the transmitter zeroed for a new installation or after a mounting-position change?

Pressure transmitters experience a small offset error due to the hydrostatic head of the silicone oil fill when the transmitter is mounted in any position other than the calibrated upright position.

The 7MF4033 can be zero-adjusted in the field using either the pushbutton on the transmitter housing (apply the reference pressure, press the zero button) or via HART communication from a handheld communicator.

The zero adjustment corrects for mounting position offsets without affecting the span, and does not change the physical calibration of the measuring cell.