Integrating SITRANS FM MAG6000 on PROFIBUS DP with S7 PLCs

Overview

The Siemens SITRANS FM MAG5100 electromagnetic flow sensor combined with the SITRANS FM MAG6000 transmitter is a work-horse combination for conductive liquid measurement in water, wastewater, chemical, and process industries. When the application specifies a PROFIBUS DP connection into a SIMATIC S7-300, S7-400, ET 200S, or S7-1500 (with PROFIBUS CM), the engineering team faces several decisions that the field rarely documents: which GSD file to import, which profile to use, how to read process values without SIMATIC PDM, and what the engineering units are on the wire.

This reference consolidates the wiring, GSD selection, hardware configuration, and cyclic data extraction steps required to bring a MAG6000 online on PROFIBUS DP. It is written for the engineer at the panel during commissioning, not the marketing engineer at the desk. The MAG6000 transmitter is the device on PROFIBUS; the MAG5100 (or MAG1100, MAG3100, MAG5100 W) sensor is the flow tube that feeds it. The pair is treated as one PROFIBUS DP-V0 slave at a unique station address.

The MAG5000/6000 product family evaluates the electrode signals from the associated sensor, converts them into a standardized 4 to 20 mA analog output and a PROFIBUS PA/DP process value, and exposes the full diagnostics block to the automation system. The PROFIBUS interface eliminates the analog loop, the shielded twisted pair, the A/D conversion in the PLC, and the scaling math in the user program — at the cost of getting the GSD, the slot mapping, and the byte order correct.

System Architecture and Topology

A typical MAG5100/MAG6000 PROFIBUS DP segment consists of:

• Sensor: SITRANS FM MAG5100 (or MAG1100, MAG3100, MAG5100 W) — the wet flow tube containing the coils and electrodes. The MAG5100 W variant is the wafer-style version commonly used in water and waste-water duties, while the MAG3100 is the flanged ANSI/DIN version for industrial process use. Refer to the SITRANS FM MAG5100 W Operating Instructions for sensor-specific installation data.
• Transmitter: SITRANS FM MAG6000 — the PROFIBUS DP/PA-capable converter. Provides coil drive to the sensor, signal conditioning, HMI, and bus interface. Refer to the SITRANS FM MAG 5000/6000 Operating Instructions for the electrical and bus interface details.
• DP master: SIMATIC S7 CPU with PROFIBUS DP master port (CPU 31x-2 DP, CPU 41x-2 DP, ET 200S master, or S7-1500 with CM 1542-5).
• Bus medium: PROFIBUS DP cable (typically Siemens 6XV1830-0EH10 violet cable) with bus terminators active at both physical ends of the segment.
• Engineering station: SIMATIC Manager (Step 7 V5.5 / V5.6) for hardware configuration and GSD import.

PROFIBUS Profile Selection: Profile 2 vs Profile 3

Siemens ships multiple GSD files for the MAG6000, broken down by two orthogonal axes: the physical network (PA versus DP) and the application profile (Profile 2 versus Profile 3). Selecting the wrong file will not damage hardware, but the slave will fail to enter cyclic data exchange and SIMATIC Manager will report a configuration fault at startup.

PA vs DP

PROFIBUS PA (Process Automation) and PROFIBUS DP (Decentralized Periphery) are physically and electrically distinct networks. PA runs on MBP (Manchester Bus Powered) physics at 31.25 kbit/s and is intrinsically safe (Ex i) — typical of chemical and petrochemical plants. DP runs on RS-485 at 9.6 kbit/s to 12 Mbit/s, is not intrinsically safe, and is the standard fieldbus in factory automation. The MAG6000 module can be configured for either, but you must install the GSD that matches the network you are connecting to. Mixing the two will cause the slave to fail to participate in token-pass and token-handshake, and the diagnostic LED will report a parameterization fault.

For the S7 PLC and water/wastewater use case, select the PROFIBUS DP GSD. PA GSDs are only used when the MAG6000 sits on a segment behind a PA/DP coupler or link (e.g., Siemens DP/PA coupler FDC 157-0).

Profile 2 vs Profile 3

Profile 2 and Profile 3 are the two device-profile implementations of the PROFIBUS PA/DP profile for process instrumentation (NE 107 / VDI/VDE 2650):

For any new S7-1500 or S7-300 integration, select Profile 3 for DP. Profile 3 is the only profile the latest SIMATIC PDM and TIA Portal versions can fully enumerate; Profile 2 is retained for service and replacement of older devices already in the field.

Prerequisites

Before commissioning, verify the following are present and verified:

1. Hardware: MAG5100 sensor installed per the MAG5100 W Operating Instructions with gaskets, grounding rings (required for lined tubes on non-conductive piping), and a coaxial signal cable run between sensor junction box and the MAG6000 transmitter. Maximum sensor-to-transmitter separation is 50 m for the MAG6000; longer runs require the MAG6000 I (intelligent) version with the pre-amplifier in the sensor head.
2. Transmitter power: 24 V DC or 115/230 V AC depending on the MAG6000 order code. Power consumption is approximately 9 W (24 V DC, with display backlight) plus the PROFIBUS termination current.
3. PROFIBUS station address: Set on the MAG6000 keypad (Menu → Service → Bus Address). Default is 126. Set a unique address between 1 and 125 for the segment.
4. Engineering software: SIMATIC Manager Step 7 V5.5 SP4 or later, or TIA Portal V13 SP1 or later if the master is an S7-1500. SIMATIC PDM V8.2 or later is recommended for diagnostics but is not strictly required for cyclic data read.
5. GSD file: Download the GSD matching the transmitter's firmware revision. The current firmware for MAG6000 PROFIBUS modules is typically V3.04 or higher; the matching GSD ships on the same firmware download bundle.
6. PLC tag capacity: One MAG6000 occupies 4 input words (8 bytes) of process data in the standard Profile 3 mapping. Reserve 8 bytes in the I/O image or a dedicated DB.

Hardware Configuration in SIMATIC Manager

The following procedure is for SIMATIC Manager Step 7 V5.x with an S7-300 / S7-400 master. TIA Portal flow is analogous — install the GSD, drag the device from the catalog into the device configuration, and assign the PROFIBUS address.

1. Install the GSD: Open HW Config → Options → Install GSD File → Browse to the SIEM813F.GSD (Profile 3 DP) file. The MAG6000 appears in the catalog under PROFIBUS DP → Other Field Devices → Sensor → Flow → Siemens AG → MAG6000.
2. Insert the master system: Drag the MAG6000 onto the PROFIBUS DP master system line in HW Config. Assign the bus address set on the transmitter keypad (default 126 must be changed if it conflicts with the DP master at 2).
3. Slot configuration: The MAG6000 Profile 3 module exposes a fixed slot structure. Verify the default slot mapping produced by the GSD:

Total cyclic input length: 15 bytes (rounded up to 16 bytes — 2 words of padding in the I/O image). If only flow is required, the slot assignment can be reduced by deleting the unused TOT and DI slots; the MAG6000 will then only transmit the AI 1 block.

4. Save and compile: HW Config → Station → Save and Compile. The DP master is now configured to exchange data with the MAG6000 at the assigned address.
5. Download to the CPU: PLC → Download to Target → confirm the new PROFIBUS configuration.
6. Power-cycle the MAG6000: After configuration download, the MAG6000 may show a configuration fault if the slot map does not match. A power-cycle forces re-parameterization.

Reading Process Data Cyclically

Cyclic process data is read using the standard SFC14 (DPRD_DAT) and SFC15 (DPWR_DAT) system function blocks. SIMATIC PDM is a configuration and diagnostics tool, not a process data reader — cyclic I/O is the standard mechanism for process values.

Assuming the MAG6000 occupies input bytes 0–15 starting at I address offset configured in HW Config (the I address appears in the slot properties dialog), the read sequence in Structured Text or LAD is:

// LAD / FBD call
CALL  "DPRD_DAT"
  LADDR  := W#16#100          // Logical base address of the MAG6000 I area
  RET_VAL:= MW100             // Return code: 0 = no error
  RECORD := P#DB20.DBX0.0 BYTE 16   // Target: 16 bytes into DB20

After the call, DB20.DBB0 contains the AI 1 status byte, DB20.DBD1 (bytes 1–4) contains the IEEE-754 single-precision volume flow value in the configured engineering unit, DB20.DBB5 starts the TOT 1 block, and so on. The same record can be read with a single SFC14 call covering all 16 bytes — no per-slot call is required.

Engineering Units and Scaling

The MAG6000 ships from the factory with volume flow in cubic metres per hour (m³/h). The PROFIBUS process value is transmitted as a 32-bit IEEE-754 floating-point number; the engineering unit is configured on the transmitter keypad (Menu → Setup → Units) and is independent of the bus representation. The unit configured on the device is the unit the PLC will see in the floating-point word.

For an S7 program that expects litres per second, the engineer has two clean options:

1. Reconfigure the transmitter to L/s on the keypad and let the floating-point value represent L/s directly.
2. Keep m³/h and convert in the PLC: L/s = (m³/h) × 1000 / 3600 = (m³/h) × 0.2777778

Option 2 is preferred for serviceability — the transmitter stays at the factory default and any future replacement unit is automatically in the expected unit. The conversion constant can be put in a constant block (FC with VAR_CONST) so the multiplier is documented in the program.

Cyclic I/O vs SIMATIC PDM

A common misconception is that PROFIBUS process values can only be read via SIMATIC PDM. This is incorrect:

SIMATIC PDM is the correct tool for parameterization, but the running volume flow value in the PLC program must be read cyclically. Do not implement an SFC59 / RDREC loop in the OB1 to fetch the flow value — that wastes bus bandwidth and will overrun the device. The PROFIBUS master poll cycle on the DP segment is the correct mechanism.

Acyclic Parameter Access from S7

For applications that need to read non-cyclic data (e.g., empty-pipe detection flag, full diagnostics buffer, calibration date), use the acyclic READ/WRITE record services from the DP master:

// Acyclic read example (S7-300/400, SIMATIC Manager)
CALL  "RDREC"
  REQ   := TRUE
  ID    := W#16#100           // Logical address of the MAG6000
  INDEX := 0                  // Slot 0 record index
  MLEN  := 16
  VALID := M105.0
  ERROR := M105.1
  STATUS:= MW106
  LEN   := MW108
  RECORD:= P#DB30.DBX0.0 BYTE 16

Slot 0 / Index 0 returns the standard PROFIBUS PA profile 3.0 diagnostics block — including the NE 107 condensed status, the device serial number, the manufacturer ID (0x810F for Siemens MAG family), and the operating hours counter. Calling this on demand from the HMI or the engineering workstation gives a maintenance engineer full visibility into the transmitter state without a field visit.

Function Block Libraries for S7

There is no Siemens-supplied, official faceplate FB for the MAG6000 in the standard Step 7 library set. For a structured integration, the recommended practice is to wrap the SFC14 read and the scaling logic in a project-specific FB:

FUNCTION_BLOCK FB200 "MAG6000_Flow_In"
VAR_INPUT
  i_LogicalAddress : INT;          // I-address from HW Config
END_VAR
VAR_OUTPUT
  o_VolumeFlow_m3h : REAL;         // Volume flow in m³/h
  o_Totalizer_m3   : REAL;         // Forward total in m³
  o_Status         : BYTE;          // NE 107 status (0=OK, 1=Maintenance, ...)
  o_Error          : BOOL;         // SFC14 RET_VAL <> 0
END_VAR
VAR
  s_DPRD_DAT : SFC14;              // Cyclic read
  s_DataBuffer : ARRAY[0..15] OF BYTE;
END_VAR
BEGIN
  s_DPRD_DAT(LADDR := WORD#16#100, RET_VAL := #o_Error, RECORD := #s_DataBuffer);
  // Slot 0: AI 1, bytes 1..4 = volume flow IEEE-754
  #o_VolumeFlow_m3h := REAL#0.0;
  IF NOT #o_Error THEN
    // Bit-copy 4 bytes from s_DataBuffer[1..4] into a temporary DWORD
    #o_VolumeFlow_m3h := DWORD_TO_REAL(SHL(WORD_TO_DWORD(BYTE_TO_WORD(s_DataBuffer[2])), 24) OR ...);
  END_IF;
END_FUNCTION_BLOCK

For a clean implementation in TIA Portal, drop a DPRD_DAT instruction in a function block, expose the input as a multi-instance DB, and split the 16-byte record into the AI / TOT / DI blocks in the FB. Most integrators build a single FB (typically FB200 / FB300 in the project) that handles all flow instruments on the segment by varying the i_LogicalAddress input.

Diagnostics and NE 107 Status

The MAG6000 supports the NE 107 (VDI/VDE 2650) status categories on PROFIBUS. The first byte of slot 0 (the AI 1 status byte) is encoded as follows:

Map this status byte to an HMI alarm or to a SCADA tag so the operator sees a single “flow meter health” indicator. PROFIBUS offers a clear advantage over the 4–20 mA loop here — a 4 mA output cannot distinguish between zero flow, an empty pipe, and a coil failure; the bus can.

Verification and Commissioning Checklist

Run this checklist before declaring the loop ready for production:

1. Bus diagnostic: In HW Config → PROFIBUS → Bus Diagnostics, confirm zero station failures, zero repeat counts, and zero lost frames. A non-zero repeat count indicates cable or termination issues — fix before proceeding.
2. Value validation: Force a known flow (e.g., a calibrated pump at 50 % of full scale) and confirm the value at the PLC matches the transmitter display to within the device's stated accuracy (typically ±0.4 % of flow rate at reference conditions, depending on the calibration). Note the value in the commissioning report.
3. Status byte: Verify the AI 1 status byte is 0x00 under normal flow. Artificially empty the pipe (close the upstream and downstream valves) and confirm the status byte moves to 0x80 (out of spec) within 2–3 PROFIBUS cycles. Drain cycles of less than 5 seconds indicate a properly configured empty-pipe detector.
4. Totalizer: Read the TOT 1 block from slot 1 and verify it increments monotonically with flow. Reset the totalizer from SIMATIC PDM (or from the transmitter keypad) to confirm the write path is operational if a reset is required for the application.
5. Power loss recovery: Power-cycle the MAG6000 and confirm the bus returns to data exchange within 10 seconds — well under the typical PLC warm restart window.
6. HMI / SCADA tag: Confirm the engineering unit (m³/h or L/s as configured) is correctly displayed in the HMI faceplate. A common bug is to display the raw float with the default decimal place from the project, leading to readouts of "123.45 m³/h" when the actual is "1.2345 m³/h". Use the unit code from the PROFIBUS slot descriptor (byte 1 of the AI block) to drive the HMI suffix.

Troubleshooting Matrix

Field-Proven Notes

• Default address trap: The MAG6000 ships at PROFIBUS address 126 — the same address the master typically uses for a new device. Change the address on the keypad before connecting the device, or the master will not find the device on commissioning day.
• Coil current verification: A common field test is to measure the coil drive current at the MAG6000 terminals — it should be approximately 125 mA per coil with the sensor connected. A reading of 0 mA indicates a broken coil or a damaged internal cable.
• Grounding: MAG flowmeters require a process-side ground reference. On lined tubes (PTFE, hard rubber), use the supplied grounding rings or grounding electrodes. Without a process ground, the electrodes pick up common-mode noise and the PROFIBUS value will be unstable.
• Power supply margin: The MAG6000 PROFIBUS option draws its bus-side power from the transmitter 24 V supply, not from the bus. If the segment is at the end of a long run, a weak 24 V supply can cause the transmitter to drop off and rejoin the bus intermittently. Verify the 24 V supply stays above 21.6 V under full load.
• Firmware upgrades: Newer MAG6000 firmware (V3.04 and later) introduced enhanced NE 107 diagnostics. If the bus diagnostic shows "manufacturer-specific diagnostic pending," the GSD needs to be upgraded to enumerate the new diagnostic bytes. Always re-import the GSD and re-download HW Config after a firmware upgrade.