Sensor Offset, Suppress Point, Switching Down

EXCEL 50/100/500/600/800

ATTRIBUTES

Pseudo totalizers: In the event that you have selected the datapoint type "pseudo totalizer inputs," you must set the attribute "Scaling Factor" to "1"; otherwise, the number of pseudo totalizer inputs will not be counted.

Sensor Offset

The attribute “Sensor Offset” is designed for the compensation of the resistance of the sensor wiring for low-resistance sensors, like Pt 100, Pt 1000, Balco 500.

The voltage offset due to the wire resistance is approximately constant, the attribute “Sensor Offset” functionality has therefore been designed to compensate constant voltage offsets at the analog input.

Function principle The principle is that the attribute “Sensor Offset” can be defined at a selected tem- perature, e.g., 1 °C at 20 °C. The Excel controller processes this temperature offset into a voltage offset, e.g., -0.11 V, and applies this very voltage offset for correcting (offsetting) all voltages measured.

In order to display a temperature, the controller processes the resulting voltage back into a temperature. This principle and the processing (including mathematical rounding) from “°C” into “volt” and back into “°C” leads to slightly inconstant offsets across the temperature range.

Example for a selected “Sensor Offset” of 1°C:

Measured Temperature	Corrected Temperature
20°C	19°C
-10°C	-8,4°C

For XFL and XFC I/O modules, "Sensor Offset" functionality is supported from

CARE 5.0 and controller firmware 2.06.05 onwards.

CAUTION

Regarding sensor offset, the behavior of controllers with OS < 2.06.05 engineered using CARE 4 differs significantly from controllers with OS 2.06.05 and higher engineered using CARE 7 and higher.

For example, for XL50 internal AI and XL500 internal AI (XF521/527 modules), the sensor offset is subtracted from the datapoint value.

For XL50 and XL800 controllers using XF821 modules, the sensor offset is added to the datapoint value.

See also section “Sensor Offset Handling” in Excel CARE – User Guide (EN2B-0182GE51).

Suppress Point

The attribute "Suppress Point" means that datapoints are no longer processed and checked. As a result, no alarms are generated for suppressed points. Where you have flexible datapoints, this attribute acts upon all basic types of physical datapoints.

IMPORTANT

Never suppress a datapoint used via your application program. This causes system failure.

Switching Down

The attribute "Switching Down" is used in conjunction with flexible datapoints of the type "feedback". On switching down from one stage to another, it determines

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