SCD_KTYSensor (FB)

SCD_KTYSensor FB scales the ADC value to temperature (°C). This function block uses a built-in calibration base curve (in SCD_SetKTYScale (FB)) for KTY sensors which can be adjusted with two input variables.

KTY sensor type can be selected with i_ResAt25degC input. This input defines the sensor’s typical resistance in 25°C temperature and shifts the calibration curve accordingly. (The typical resistance in 25°C is told in the sensor’s data sheet).

However, there are some differences in individual sensors and therefore it might be necessary to fine tune the calibration curve for better accuracy. For that purpose there is i_CalibrationOffset input. i_CalibrationOffset shifts the calibration curve, keeping the curve shape. Shift amount is given in Ohms at 25°C. The ideal value for calibration offset is normally found only by testing.

The sensor’s nominal calibration curve is only valid with a certain supply current, therefore the curve may also need fine tuning because of differences in supply current in different type of connections. Also, the reference voltage (sensor supply voltage) level affects the calibration offset. (Supply current is much bigger when using current input i.e. 220ohm pull-down resistor.)

Limitations

Inputs

Input variable name	Data type	Range	Description
i_Enable	BOOL	TRUE/FALSE	Enables calculation of outputs
i_SensorAIValue	WORD	hardware specific	AD converter value from sensor
i_SensorAIType	BYTE	0..G_ADScaleArrMax	Defines the AI type (mA or V) and range
i_ResAt25degC	INT	0..5000 Ohm	Sensor’s typical resistance in Ohm value at 25°C
i_CalibrationOffset	INT	-200..200 Ohm	Resistance offset value in Ohm at 25°C for fine tuning calibration curve.
i_SensorValueErrorLimitHigh	WORD	0..5000 Ohm	High error limit for sensor resistance value in Ohms
i_SensorValueErrorLimitLow	WORD	0..5000 Ohm	Low error limit for sensor resistance value in Ohms
i_CalibratedValueAlarmLimitHigh	INT	-50..150°C	High alarm limit for temperature output value in °C
i_CalibratedValueWarningLimitHigh	INT	-50..150°C	High warning limit for temperature output value in °C
i_CalibratedValueWarningLimitLow	INT	-50..150°C	Low warning limit for temperature output value in °C
i_CalibratedValueAlarmLimitLow	INT	-50..150°C	Low alarm limit for temperature output value in °C
i_ReferenceAIValue	WORD	hardware specific	AD converter value of the reference voltage that is used to supply the sensor.
i_ReferenceAIType	BYTE	0..G_ADScaleArrMax	Defines the AI range of reference measurement
i_EnableCalibratedValueOutput	BOOL	TRUE/FALSE	Enables temperature calculation, when false temperature output value is 0°C.
i_EnableSensorValueErrors	BOOL	TRUE/FALSE	Enables sensor resistance value diagnostics
i_EnableCalibratedValueHighAlarm	BOOL	TRUE/FALSE	Enables temperature high alarm
i_EnableCalibratedValueHighWarning	BOOL	TRUE/FALSE	Enables temperature high warning
i_EnableCalibratedValueLowWarning	BOOL	TRUE/FALSE	Enables temperature low warning
i_EnableCalibratedValueLowAlarm	BOOL	TRUE/FALSE	Enables temperature low alarm
i_ErrorDelay	UINT	0..65535 ms	Error delay in milliseconds

Input variable name	Data type	Range	Description
i_Enable	BOOL	TRUE/FALSE	Enables calculation of outputs
i_SensorAIValue	WORD	hardware specific	AD converter value from sensor
i_SensorAIType	ADData	G_AIType struct	Defines the AI type (mA or V) and range
i_ResAt25degC	INT	0..5000 Ohm	Sensor’s typical resistance in Ohm value at 25°C
i_CalibrationOffset	INT	-200..200 Ohm	Resistance offset value in Ohm at 25°C for fine tuning calibration curve.
i_SensorValueErrorLimitHigh	WORD	0..5000 Ohm	High error limit for sensor resistance value in Ohms
i_SensorValueErrorLimitLow	WORD	0..5000 Ohm	Low error limit for sensor resistance value in Ohms
i_CalibratedValueAlarmLimitHigh	INT	-50..150°C	High alarm limit for temperature output value in °C
i_CalibratedValueWarningLimitHigh	INT	-50..150°C	High warning limit for temperature output value in °C
i_CalibratedValueWarningLimitLow	INT	-50..150°C	Low warning limit for temperature output value in °C
i_CalibratedValueAlarmLimitLow	INT	-50..150°C	Low alarm limit for temperature output value in °C
i_ReferenceAIValue	WORD	hardware specific	AD converter value of the reference voltage that is used to supply the sensor.
i_ReferenceAIType	ADData	G_AIType struct	Defines the AI range of reference measurement
i_EnableCalibratedValueOutput	BOOL	TRUE/FALSE	Enables temperature calculation, when false temperature output value is 0°C.
i_EnableSensorValueErrors	BOOL	TRUE/FALSE	Enables sensor resistance value diagnostics
i_EnableCalibratedValueHighAlarm	BOOL	TRUE/FALSE	Enables temperature high alarm
i_EnableCalibratedValueHighWarning	BOOL	TRUE/FALSE	Enables temperature high warning
i_EnableCalibratedValueLowWarning	BOOL	TRUE/FALSE	Enables temperature low warning
i_EnableCalibratedValueLowAlarm	BOOL	TRUE/FALSE	Enables temperature low alarm
i_ErrorDelay	UINT	0..65535 ms	Error delay in milliseconds

Outputs

Output variable name	Data type	Range	Description
o_SensorValue	INT	0..5000 Ohm	Sensor resistance value in Ohm, calculated from sensor ADC value.
o_CalibratedValue	INT	-50..150°C	Temperature value based on calibration
o_ParameterError	BOOL	TRUE/FALSE	Always FALSE. Included in the block for compatibility reasons
o_SensorValueErrorHigh	BOOL	TRUE/FALSE	Sensor value too high
o_SensorValueErrorLow	BOOL	TRUE/FALSE	Sensor value too low
o_CalibratedValueHighAlarm	BOOL	TRUE/FALSE	Temperature over the high alarm limit
o_CalibratedValueHighWarning	BOOL	TRUE/FALSE	Temperature over the high warning limit
o_CalibratedValueLowWarning	BOOL	TRUE/FALSE	Temperature below the low warning limit
o_CalibratedValueLowAlarm	BOOL	TRUE/FALSE	Temperature below the low alarm limit

Output variable name	Data type	Range	Description
o_SensorValue	INT	0..5000 Ohm	Sensor resistance value in Ohm, calculated from sensor ADC value.
o_CalibratedValue	INT	-50..150°C	Temperature value based on calibration
o_SensorValueErrorHigh	BOOL	TRUE/FALSE	Sensor value too high
o_SensorValueErrorLow	BOOL	TRUE/FALSE	Sensor value too low
o_CalibratedValueHighAlarm	BOOL	TRUE/FALSE	Temperature over the high alarm limit
o_CalibratedValueHighWarning	BOOL	TRUE/FALSE	Temperature over the high warning limit
o_CalibratedValueLowWarning	BOOL	TRUE/FALSE	Temperature below the low warning limit
o_CalibratedValueLowAlarm	BOOL	TRUE/FALSE	Temperature below the low alarm limit

Reference voltage level (V)	Connection type	CalibrationOffset (Ohm@25°C)
+10V	Voltage input (type 2)	30
+5V	Voltage input (type 2)	5
+10V	Current input (type 1)	out of spec
+5V	Current input (type 1)	70

SCD_KTYSensor (FB)

Description

Limitations

Inputs

Outputs

Example code

See also