DACA Block – Programming Logic Documentation

Overview

The DACA (Digital Analog Comparison Alarm) DACA is a fundamental aspect of our programming infrastructure, acting as the primary gateway for data processing. It plays a crucial role in ensuring that data is collected, processed, and distributed with the highest level of accuracy and efficiency throughout the control system.

In the DACA module, we initially receive raw signals from the PLC, which are then converted into a desired engineering range that is optimized for further analysis and processing. This conversion is essential to maintain the integrity and usability of the data as it flows through the automation logic.

Logic Block Illustration

The diagram above shows a simple representation of the fb_DACA logic block instance DACA. This block is designed to process an analog signal input (INPUT) and generate a scaled output (PV) suitable for monitoring or control logic.

In the above picture, we connect input raw signal to the DACA block.

In the above picture, we are showing the initialization parameters.

DACA Function Block – Pin Information

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Signal	Type	Description
INPUT	WORD	Raw analog input value from the field sensor.
PV_LO	REAL	Set low process value range.
PV_HI	REAL	Set high process value range.
RTN_ACK_REQD	BIT	Set to TRUE if Return-To-Normal alarm requires user acknowledgment.
ACK	BIT	Alarm acknowledgment input from operator.
PVLL	REAL	Very Low PV alarm threshold.
PVLO	REAL	Low PV alarm threshold.
PVHI	REAL	High PV alarm threshold.
PVHH	REAL	Very High PV alarm threshold.
HYST	REAL	Hysteresis value to avoid alarm flickering.
FILTER	REAL	Filter constant to reduce noise on input signal.
In_Type	BOOL	Input Type TRUE := Square root, FALSE := Linear.
Acknowleged	BIT	High if alarm was acknowledged.
WireBreak	BIT	High if wire is broken.
WireShort	BIT	High if wire is shorted.
PV_LL_ALM	BIT	High when very low alarm is active.
PV_LO_ALM	BIT	High when low alarm is active.
PV_HI_ALM	BIT	High when high alarm is active.
PV_HH_ALM	BIT	High when very high alarm is active.
PV	REAL	Scaled process value (calculated from raw input and PV range).
TagName	STRING(10)	Short tag identifier for block (max. 10 characters).
Desc	STRING(12)	Short description for block (max. 12 characters).

Training Demo Video

Demonstration video is available , How to use the Daca Logic Block through Library:

PID Block Demo - TPW Logic Setup

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Simplified Notes

Alarm Logic:

• Alarms (PV_LO_ALM, PV_HI_ALM, etc.) activate when PV crosses configured thresholds (PVLO, PVHI, etc.).
• Acknowledge the alarm using ACK input. Once cleared and acknowledged, Acknowleged becomes TRUE.

Fault Detection:

• WireBreak and WireShort help detect sensor or wiring issues automatically.

Process Scaling:

• The raw INPUT value is scaled between PV_LO and PV_HI to compute the actual PV.

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Tip: Use the FILTER input to reduce signal jitter in noisy environments. Set HYST to introduce deadband and reduce alarm chattering.

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