Deploying the SITRANS Library in SIMATIC PCS 7 V8.2: MAG 6000, SIPART PS2, and Redundant S7-400H Limitations

In SIMATIC PCS 7 V8.2, integrating Siemens field instruments (such as SITRANS MAG 6000 flowmeters and SIPART PS2 valve positioners over PROFIBUS PA/DP or HART) can be streamlined using the dedicated SITRANS Library for PCS 7 (SIOS Entry ID: 65741624). The library provides specialized function blocks and faceplates that expose advanced diagnostic variables and calibration parameters. However, in redundant S7-400H controller architectures, the SITRANS Library V6.0 cannot be deployed with certain PROFIBUS PA devices (specifically SIPART PS2), triggering permanent QWRONDEV (Wrong Device) error status. This occurs because the SITRANS block cyclically transmits acyclic DPV1 identity verification commands that the field instrument cannot answer across redundant DP master switches. For redundant S7-400H systems, Siemens mandates using standard PCS 7 APL channel blocks (Pcs7AnIn, Pcs7AnOu, VlvAnL) instead.

Overview and Purpose of the Siemens SITRANS Library in PCS 7

The standard PCS 7 Advanced Process Library (APL) provides generalized channel blocks (Pcs7AnIn, Pcs7DiIn) that read raw 4-20 mA or standard 5-byte PROFIBUS PA process values. However, modern smart instruments generate vast arrays of secondary diagnostics: sensor coil impedance, totalized mass volumes, partial stroke test results, and valve travel histograms.

To expose this intelligence without complex user coding, Siemens released the SITRANS Library for PCS 7 (Entry ID: 65741624). It contains tailored blocks and WinCC faceplates specifically engineered for Siemens SITRANS transmitters and SIPART valve positioners, blending seamlessly into the APL graphic philosophy.

Key Instrument Driver Blocks: MAG 6000, TH300, and SIPART PS2

The library contains dedicated functional packages:

MAG 6000 Block (MAG6K): Interfaces SITRANS F M MAG 6000 electromagnetic flowmeters over PROFIBUS PA/DP or HART. Reads multi-variable process data (volumetric flow, mass flow, flow velocity) and totalizer counters, and manages batch dosing.
TH300 / TH400 Block (SITR_TH): Manages temperature transmitters, monitoring thermocouple resistance and RTD sensor drift (Entry ID: 109747401).
SIPART PS2 Block (PS2): Interfaces the SIPART PS2 electropneumatic positioner, executing automated valve initialization, partial stroke testing (PST), and valve friction monitoring.

The Acyclic DPV1 Bottleneck in Redundant S7-400H Architectures

While the SITRANS Library operates flawlessly on single controller architectures (standard S7-400 or CPU 410 single), deployment on redundant S7-400H / CPU 410-5H Redundant pairs reveals a critical architectural limitation:

Device Identification Check: When the PS2 block initializes, it sends an acyclic DPV1 read command (RDREC) from the CPU to verify that the connected field hardware matches the expected device type.
H-System Redundancy Rejection: Most legacy PROFIBUS PA field instruments (including older SIPART PS2 firmware) do not support redundant acyclic master handshaking through DP/PA couplers. The instrument fails to respond to the acyclic query from the secondary/redundant master.
Persistent QWRONDEV Alarm: Receiving no answer or an invalid response, the SITRANS block asserts output QWRONDEV = 1 ('Wrong Device Connected') and halts all cyclic control commands to the valve!

Resolving the QWRONDEV Error and Fallback to Standard APL Blocks

Because QWRONDEV cannot be bypassed in the compiled SITRANS V6.0 code on redundant systems, Siemens mandates the following engineering resolution:

Revert to Standard APL Channel Blocks: In CFC, replace the SITRANS PS2 block with the standard APL analog output block Pcs7AnOu (or FbAnOu) combined with VlvAnL (Analog Valve).
Preserve Cyclic Exchange: The standard APL blocks utilize purely cyclic PROFIBUS DP/PA process image data (control setpoint and position feedback) without sending intrusive acyclic DPV1 identity checks.
Parameterization via PDM: To perform partial stroke testing or calibrate the SIPART PS2 in a redundant system, perform these operations acyclically through SIMATIC PDM via a secondary master or engineering station link rather than through continuous controller block calls.

Comparison of SITRANS Library vs Standard PCS 7 APL Drivers

The following table compares the capabilities and system compatibility of the SITRANS Library versus standard PCS 7 APL drivers:

| Feature Dimension | SITRANS Library (V6.0 / Modern) | Standard PCS 7 APL Library |
|---|---|---|---|
| Redundant S7-400H Support | Limited (Incompatible with PA SIPART PS2) | 100% Fully Certified on S7-400H |
| Secondary Variable Ingestion | Fully Automated (Totalizers, Sensor Temp) | Requires custom acyclic reading or manual mapping |
| Advanced Valve Testing | Native Partial Stroke Testing (PST) in faceplate | Requires custom SFC logic or manual PDM test |
| Acyclic Device Verification | Mandatory (Triggers QWRONDEV on fail) | None (Operates purely on cyclic process data) |
| WinCC Faceplate Views | Detailed diagnostic, calibration, and maintenance | Standard, Parameter, Trend, Alarm, Memo |

Verification

Verify field instrument communication in PCS 7:
1. On a single controller system, monitor the MAG6K block in CFC test mode; verify that QWRONDEV is false (0) and that volumetric flow and totalizer values match physical meter readings.
2. In WinCC Runtime, open the SITRANS MAG 6000 faceplate; confirm that live flow curves, sensor coil health, and totalizer counters update cleanly.
3. If operating on a redundant S7-400H system with standard APL blocks, verify that VlvAnL modulates the SIPART PS2 positioner smoothly and receives 4-20 mA position feedback without communication fault alarms.

Limitations and Operational Precautions

Always consult the SITRANS Library release notes and device compatibility matrix before incorporating SITRANS blocks into a redundant S7-400H project. Never attempt to use SITRANS Library blocks with third-party instruments (such as Endress+Hauser or Emerson transmitters); the internal device identification algorithms will reject the hardware and assert QWRONDEV. Third-party instruments should always be interfaced using standard APL channel blocks.

Engineer FAQ

Where can I download the SITRANS Library for PCS 7?

The SITRANS Library is available on Siemens Industry Online Support under Entry ID 65741624.

Why does the SIPART PS2 show QWRONDEV in an S7-400H redundant system?

Because the field device cannot respond to acyclic DPV1 identity verification requests sent by the redundant H-master architecture, causing the block to assume an incompatible instrument is connected.

Can I calibrate a SIPART PS2 if I use standard APL blocks instead of the SITRANS Library?

Yes. Calibration, stroke tuning, and parameterization can be performed using SIMATIC PDM across the bus without requiring the SITRANS runtime block in CFC.