Analog Register Block

Purpose

The Analog Register (AR) block reads and writes analog values to process hardware. It provides both input and output capacity in a single block using a minimum amount of memory because iFIX only processes the block when a picture that references it is open.

Features

The Analog Register block:

• Is a primary block.
• Is always a stand-alone block.
• Sends and receives values from an I/O driver or OPC server.
• Requires no SAC processing.
• Lowers CPU overhead when compared to an Analog Input block and increases SAC performance.
• Is processed when the picture containing the Analog Register block is displayed in the iFIX WorkSpace, even when SAC is not running. The block is not processed when another picture is displayed or when the operator exits the iFIX WorkSpace.
• Accepts pulse count or word value (register) analog signals, which are then converted to engineering units (EGU) for viewing.
• Accesses up to 1024 Analog points in the same poll record.
• Does not support alarming.
• Can use linear scaling on values received. The following formula is used to determine the linear scale value:

The equation for a line is Y = mX + b

Where Y is the scaled output value, X is the raw value from the PLC, m is the slope of the line and b is the y intercept.

The slope for our linearization is defined by output range divided by the input.

m  =  (ScaleHigh - ScaleLow ) / (RawHigh - RawLow)

The y intercept is determined by using the low values and the slope.

b = ScaleLow - m(RawLow)

In the analog block this results in the block's current value is equal to the driver value times the slope plus the y intercept.

X_CV = (IO value)m + b  

The driver value equates to the block current value minus the y intercept divided by the slope.

IO Value = (X_CV – b) / m

Typical Uses

Example

Fields