Displaying Raw Field Channel Values in WinCC Analog Faceplates

Displaying raw field transmitter values alongside simulated process values on WinCC analog faceplates allows operators to observe live process conditions without causing uncommanded trips during online maintenance. Directly modifying standard faceplate pictures like @PG_MonAnS_Standard.pdl is strongly discouraged because changes are overwritten whenever the OS Project Editor executes and require tedious manual replication across distributed OS servers and clients. The standard, robust engineering solution utilizes the Advanced Process Library (APL) block MonAnL (FB1845) instead of the compact block MonAnS (FB1910). By interconnecting the raw field value to the UserAna1 input and defining an engineering identifier, WinCC natively displays the live field value on the faceplate without custom PDL edits.

Architectural Differences: MonAnL vs MonAnS

The SIMATIC PCS 7 Advanced Process Library provides two distinct monitoring blocks for analog measurements: MonAnL (FB1845 - Large/Standard) and MonAnS (FB1910 - Small). Understanding their structural differences explains why auxiliary display requirements should be implemented at the CFC block level rather than through graphical manipulation.

Feature / CapabilityMonAnS (FB1910 - Small)MonAnL (FB1845 - Standard)Engineering SignificanceProcess Object (PO) Count1 PO1 POSame license consumption on modern PCS 7 AS controllers.Auxiliary Analog InputsNoneUserAna1, UserAna2Allows interconnecting live field channels, redundant transmitters, or calculated values.Simulation HandlingSimOn, SimPV_InSimOn, SimPV_In, SimLiOpBoth blocks support simulation, but MonAnL displays secondary live signals simultaneously.Gradient MonitoringNoYes (GradEn, GradHILim, GradLoLim)Detects rapid transmitter drift or rate of change.Maintenance ViewsBasic standard viewStandard, Limit, Trend, Parameter, PreviewMonAnL provides dedicated operator and maintenance diagnostic views.Faceplate Picture File@PG_MonAnS_Standard.pdl@PG_MonAnL_Standard.pdlMonAnL standard view automatically renders UserAna1 if connected and enabled.

Implementation Procedure via MonAnL UserAna1

The recommended engineering method routes the un-simulated field channel output to MonAnL.UserAna1 in Continuous Function Chart (CFC):

Channel Driver (Pcs7AnIn)                 Analog Monitoring (MonAnL)
+-----------------------+                 +-----------------------+
|                       |                 |                       |
| PV_Out (Real)         +---------------->+ PV                    |
| (or Raw Field Value)  |                 |                       |
|                       +---------------->+ UserAna1              |
| Bad (Bool)            |                 |                       |
+-----------------------+                 | SimOn   (Active = 1)  |
                                          | SimPV_In (Sim Value)  |
                                          +-----------------------+

Configuration Steps

In the PCS 7 CFC editor, replace instance MonAnS with MonAnL (FB1845).
Interconnect the primary output PV_Out of the signal driver (Pcs7AnIn FB1869) to MonAnL.PV.
Interconnect Pcs7AnIn.PV_Out (or raw integer value Pcs7AnIn.PV_In converted to Real) to MonAnL.UserAna1.
In the block properties of MonAnL in CFC:
- Navigate to parameter UserAna1.
- Set attribute Identifier (or text property) to "Live Channel" or "Field Value".
- Set UserAna1Unit to match the process unit code (e.g., 1001 for °C or 1000 for %).
Compile the CFC charts (Changes Only).
Run OS Compilation (Changes Only).
In WinCC Runtime, open the faceplate for the analog tag. The auxiliary display row dynamically appears below the main process value bar, clearly showing "Live Channel: 45.2 °C" even when simulation mode (SimOn = 1) overrides the primary PV display.

Direct Faceplate Modification Risks & Overwrite Protection

When an engineer chooses to force raw channel visibility by copying and editing @PG_MonAnS_Standard.pdl inside the WinCC GraCS folder:

OS Project Editor Overwrites: Running the OS Project Editor in WinCC Explorer defaults to restoring all standard @*.pdl files from the Siemens installation template directory (<PCS7_Path>\WinCC\options\pdl\). Any custom static text or I/O fields added to @PG_MonAnS_Standard.pdl are wiped out without warning.
Multi-Station Replication: Modified PDLs must be manually copied to every Single Station, OS Server 1, OS Server 2, and all OS Reference Clients. If one station is omitted, operators experience broken script calls or inconsistent views.
Firmware & Update Vulnerability: During PCS 7 updates (e.g., V8.2 Upd1 or V9.0 migration), Siemens updates internal ODK scripts inside @PG_*.pdl. Custom-modified PDLs will either revert or become incompatible with updated APL runtime DLLs.

[!TIP]
If a custom faceplate cannot be avoided, create an entirely new block icon and faceplate picture set with a custom name prefix (e.g., @PG_MonAnCustom_Standard.pdl) and assign this custom type in the block properties, rather than modifying standard Siemens @PG_*.pdl files directly.

Verification

To verify that the auxiliary value renders reliably without modifying system faceplates:

In WinCC Runtime, locate and click the block icon for the reconfigured analog point.
Verify that the standard faceplate view opens without graphical errors or missing tag warnings in WinCC_Sys.log.
Confirm that the auxiliary row displays the configured identifier (Live Channel) and the live field reading.
Activate simulation mode on the block (SimOn = 1) and adjust SimPV_In to a simulated test value (e.g., 85.0 bar).
Observe the faceplate display:
- The primary analog display and bar indicator show the simulated value (85.0 bar) with the yellow simulation indicator flag active.
- The auxiliary UserAna1 display continues to track the actual live field transmitter reading, verifying that live field conditions remain fully visible.

Limitations and Operational Precautions

Operational boundaries when utilizing auxiliary inputs:

Alarm Suppression in Simulation: When SimOn = 1, all high/low alarms evaluate against the simulated process value (SimPV_In), NOT against UserAna1. Operating personnel must remain aware that high field process deviations will not generate audible safety alarms if the primary value is forced into a normal range.
Archive Tagging: WinCC tag logging typically archives only PV_Out.Value. If historical trends of both simulated and raw field channels are required simultaneously, create a separate archive tag linked to UserAna1.Value.
Faceplate Height Adaptation: When UserAna1 is active, the APL faceplate automatically expands its vertical dimensions to accommodate the auxiliary row. Ensure surrounding picture layouts allow room for expanded faceplates.

Engineer FAQ

Can I rename the UserAna1 label dynamically from the WinCC OS?

Yes. The label text is sourced from the Identifier property of the CFC block parameter. Modifying this in CFC and compiling the OS updates the WinCC Text Library. Alternatively, you can edit the string directly in the WinCC Text Library under the APL language table.

Does MonAnL consume more AS memory than MonAnS?

Yes, MonAnL requires slightly more controller memory (approx. 750 bytes of work memory compared to 350 bytes for MonAnS) due to gradient calculation, flutter suppression, and auxiliary signal processing. However, both consume exactly 1 Process Object (PO).

How can I display the raw transmitter 4-20 mA current instead of scaled engineering units?

Connect the raw count or mA value from the input driver block (such as Pcs7AnIn.PV_In or an auxiliary scaling block Scale) directly to UserAna1, and set UserAna1Unit to mA (code 1003).

What happens to UserAna1 if the field transmitter wire breaks?

If the input channel faults, Pcs7AnIn.Bad asserts. If UserAna1 is connected to Pcs7AnIn.PV_Out, its signal status byte will transition to 16#00 (Bad), causing the faceplate auxiliary row to display the red cross icon indicating invalid quality code.