ResistanceSensor (FB)

Epec Programming and Libraries Manual

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Supported platforms: CODESYS 3.5

ResistanceSensor (FB)

Description

This FB calibrates linear resistance sensor value i_InputValue (mV) to SI unit (°C, bar, km/h, kg, etc…).

To operate correctly it is required that sensor operates linearly.

Calibrated output value and alarm/warning limits are the same unit than input variables i_OutputMin and i_OutputMax.

Enabled alarm/warning limits are sanity checked: i_HighAlarmLimit > i_HighWarningLimit > i_LowWarningLimit > i_LowAlarmLimit. Deviation cause parameter error.

The output values o_CalibratedValue and o_Resistance are set to zero if i_Enable is FALSE, or parameter error is diagnosed.

All internal FB initializations are done on the rising edge of i_Enable.

All errors are reset on the rising edge of i_Enable.

Limitations

This FB can only be used with a linear resistance sensor connected to a voltage input.

The FB uses internally

- S_VoltageToResistance FB from SafeConversion library.

- S_ValueDiagnostic FB from SafeDataValidation library.

Following parameters are taken into use at the rising edge of i_Enable:

- i_ResistanceHigh

- i_ResistanceLow

- i_OutputMin

- i_OutputMax

- i_InternalPullUpResistance

- i_InternalPullDownResistance

- i_HighAlarmLimit

- i_HighWarningLimit

- i_LowWarningLimit

- i_LowAlarmLimit

- i_EnableHighAlarm

- i_EnableHighWarning

- i_EnableLowWarning

- i_EnableLowAlarm

- i_DiagnosticDelay

+ Any initialized event code.

Inputs

Input variable name	Data type	Range	Description
i_Enable	BOOL	FALSE/TRUE	Enable operation.
i_InputVoltage	DINT	-	Measured voltage (mV) of sensor.
i_ReferenceVoltage	DINT	-	Measured supply voltage (mV) of sensor.
i_ResistanceHigh	DINT	-	Maximum resistance value of the sensor (Ohm).
i_ResistanceLow	DINT	-	Minimum resistance value of the sensor (Ohm).
i_OutputMin	DINT	-	Minimum SI-unit value of the sensor, corresponds to i_ResistanceLow.
i_OutputMax	DINT	-	Maximum SI-unit value of the sensor, corresponds to i_ResistanceHigh.
i_InternalPullUpResistance	EPEC_HW. PULL_UP_RESISTANCE	ENUM	Internal pull-up resistance of AI input (Ohm).
i_InternalPullDownResistance	EPEC_HW. PULL_DOWN_RESISTANCE	ENUM	Internal pull-down resistance of AI input (Ohm).
i_HighAlarmLimit	DINT	-	High alarm limit for calibrated value.
i_HighWarningLimit	DINT	-	High warning limit for calibrated value.
i_LowWarningLimit	DINT	-	Low warning limit for calibrated value.
i_LowAlarmLimit	DINT	-	Low alarm limit for calibrated value.
i_EnableHighAlarm	BOOL	FALSE/TRUE	High value alarm in use.
i_EnableHighWarning	BOOL	FALSE/TRUE	High value warning in use.
i_EnableLowWarning	BOOL	FALSE/TRUE	Low value warning in use.
i_EnableLowAlarm	BOOL	FALSE/TRUE	Low value alarm in use.
i_DiagnosticDelay	UINT	-	Diagnostic delay for alarms and warnings (ms).

Outputs

Output variable name	Data type	Range	Description
o_CalibratedValue	DINT	-	Calibrated SI-unit value.
o_Resistance	DINT	-	Calculated resistance of the sensor.
o_HighAlarm	BOOL	FALSE/TRUE	Calibrated value high alarm status.
o_HighWarning	BOOL	FALSE/TRUE	Calibrated value high warning status.
o_LowWarning	BOOL	FALSE/TRUE	Calibrated value low warning status.
o_LowAlarm	BOOL	FALSE/TRUE	Calibrated value low alarm status.
o_ParameterError	BOOL	FALSE/TRUE	Error in input parameters.

EventCodeInit (Public Method)

This optional method sets pointer for event code.

Inputs

Input variable name	Data type	Description
i_Enable	BOOL	Enable operation.
i_pEventCode	POINTER TO EPEC_DITF.EventCode	Pointer to signal event code value provided by the application.

Example code

Pull-up to 5 V is selected in MultiTool Creator's AI configuration when using resistance sensors.

Example implementation is made with EC44 unit which has pull-up measurement available. For products which does not have AI pull-up measurement (e.g. SL84), use hardcoded 5000 mV value for voltage to resistance conversion's S_i_RefVoltage.

// SL84 does not have pull-up measurements, assume 5V pullup

S_TEMP_PULLUP_VOLTAGE: SAFEDINT := DINT#5000;