Observed FP4151TN Bargraph Failure
On an FP4151TN display, every bargraph remained at its maximum position even though the Graph Operation tag referenced a changing PLC variable. The variable was declared as REAL, and the HMI data type was configured as Float.
The same tag value remained readable through Show Numerical Data. This separates tag-value availability from graphical rendering: the evidence confirms that the HMI could display the value numerically, but it does not confirm whether the fault was caused by conversion, scaling, project corruption, or another bargraph-specific behavior.
Data-Type Comparison
| PLC variable type | HMI configuration or result | Observed bargraph behavior |
|---|---|---|
REAL |
Graph Operation data type set to Float
|
All bars stayed at maximum, although numerical display worked |
DINT |
The PLC variable was changed from REAL
|
The bargraph moved as intended |
This comparison supports a data-type-related workaround, not a confirmed product defect or universal incompatibility with floating-point values.
Apply the Supported Workaround
- Use
Show Numerical Datato confirm that the affected tag value is available and changing. - If the bargraph remains at maximum with the PLC variable declared as
REALand the HMI data type set toFloat, change the PLC variable used by the graph toDINT. - Run the display and verify that the bargraph now follows changes in the converted integer value.
Changing from REAL to DINT removes fractional information. Before adopting this workaround, verify that integer resolution is acceptable for the process and that the conversion does not alter the required engineering-unit range.
Verification and Remaining Unknowns
Test the bargraph at multiple process values and compare its movement with the numerical indication. Confirm that it no longer remains at maximum and that the displayed integer range preserves the required process resolution.
The available evidence does not identify firmware, bargraph limits, scaling settings, conversion rules, or an affected software version. If a floating-point signal must be retained, record those project details and escalate through the manufacturer's official support channel rather than treating the DINT workaround as proof of the root cause.
FAQ
Why does my FP4151TN bargraph stay at maximum while the value changes?
The reported case used a REAL PLC variable with the Graph Operation data type set to Float. The value appeared through Show Numerical Data, but the evidence does not establish the exact bargraph-side root cause.
How can I make an FP4151TN bargraph move again?
In the documented case, changing the PLC variable from REAL to DINT restored the intended bargraph movement. Verify the result across the required operating range.
Does changing REAL to DINT affect the displayed process value?
Yes. A DINT representation does not retain the fractional component of a REAL value, so confirm that the resulting integer resolution and range remain suitable for the process.