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<reference id="GUID-4DBE9AD9-2942-450B-B43C-3F2B47777357" xml:lang="en"><title>Scaling

Channel Data Values</title><shortdesc>The value of a channel data item can represent the actual or relative

value of the measured quantity. The relative value is a scaled value that

lies within the maximum and minimum values of the measured quantity.</shortdesc><prolog><metadata><keywords/></metadata></prolog><refbody>

<section id="GUID-D46EE015-C2B6-44AA-B021-F6AC1BB76F02">       <p>The <codeph>KSensrvPropIdChannelDataFormat</codeph> property

defines if channel data items are in a scaled format. For scaled data items,

the <codeph>KSensrvPropIdScaledRange</codeph> property defines range of the

data item value and the <codeph>KSensrvPropIdMeasureRange</codeph> property

defines range of the measured quantity.</p>     </section>

<example><p>The following example explains how the sensor data can be scaled

by reading the maximum value of measure range for data items (<codeph>KSensrvPropIdScaledRange</codeph>)

and the maximum value of the measured quantity (<codeph>KSensrvPropIdMeasureRange</codeph>).

The example considers that the <codeph>KSensrvPropIdMeasureRange</codeph> property

is defined as an array property. </p><codeblock xml:space="preserve">TSensrvProperty property;

    TInt  channelDataFormat( ESensrvFormatAbsolute );

    TInt  channelDataScaledRange( 1 );

    TReal channelDataMeasureRangeMaxValue( 1 );

    //Read channel data format

    iSensorChannel->GetPropertyL( KSensrvPropIdChannelDataFormat, KSensrvItemIndexNone, property );

    property.GetValue( channelDataFormat );

    if( ESensrvFormatScaled == channelDataFormat )

        {

        //Read data item scaled range

        iSensorChannel->GetPropertyL( KSensrvPropIdScaledRange, KSensrvItemIndexNone, property );

        property.GetMaxValue( channelDataScaledRange );

        //Read data item measure range

        iSensorChannel->GetPropertyL( KSensrvPropIdMeasureRange, KSensrvItemIndexNone, property );

        if( ESensrvArrayPropertyInfo == property.GetArrayIndex() )

            {

            TInt arrayIndex( 0 );

            property.GetValue( arrayIndex );//Value points to array index currently in use

            iSensorChannel->GetPropertyL( KSensrvPropIdMeasureRange,

                                          KSensrvItemIndexNone,

                                          arrayIndex,

                                          property );

            }

        else

            {

            //Single property

            }

        property.GetMaxValue( channelDataMeasureRangeMaxValue );

        }

    else

        {

        //No scaling needed.

        //Value of the data item represents actual value of the measured quantity.

        }</codeblock><p>You can convert the scaled channel data item value

to the absolute value by dividing the channel data item value with the maximum

value of scaled range of the channel and multiplying it with the maximum value

of the measured quantity. </p><p>For example, if the accelerometer channel

provides the following properties: </p><ul>

<li><p><codeph>KSensrvPropIdChannelDataFormat</codeph> with value <codeph>ESensrvFormatScaled</codeph></p></li>

<li><p><codeph>KSensrvPropIdScaledRange</codeph> with maximum value of 127</p></li>

<li><p><codeph>KSensrvPropIdMeasureRange</codeph> with maximum value of 2

g</p></li>

<li><p><codeph>KSensrvPropIdChannelUnit</codeph> with value <codeph>ESensrvUnitGravityConstant</codeph></p></li>

</ul><p>then the accelerometer channel data item value of 64 is equal to an

absolute value of 1.01g (that is, 64 / 127 * 2g = 1.01g).</p></example>

</refbody></reference>