Output I/O Type Sensor/Actuator Type Min/Max
Digital (Binary) (BBO)
Relay
Relay/Triac
Output
N/A N/A
1
The Analog Output microblock uses the Min and Max values to linearly translate its
EIKON for WebCTRL wire value into a physical output signal (Volt, mA, or psi) sent from
the ZN551 to an actuator. For example, set Min to 0 and Max to 100 for an Analog
Output microblock that receives a 0 to 100% open signal from a PID microblock and
that controls a 0–10 Vdc actuator so that when the PID signal is 100%, the ZN551
output is 10 Vdc. Similarly, when the PID signal is 50%, the ZN551 output is 5 Vdc.
Resolution values
Resolution is not particular to a type of input or output, but the module
driver handles analog and digital (binary) inputs and outputs differently. To
set these values appropriately, you should understand how the module driver
uses them.
Resolution Notes
Analog Input (BAI)
The driver truncates the microblock's present value according
to the resolution.
EXAMPLE If the calculated present value is 13.789 and you
set the Resolution to 0.1, the control program uses 13.7 for
any calculations downstream from the microblock.
Analog Output (BAO)
The driver truncates the wire input value to the microblock
before performing any scaling calculations.
EXAMPLE If the wire input value is 13.789 and you set the
Resolution to 0.1, the microblock uses 13.7 for any scaling
calculations.
Digital Inputs and
Outputs
N/A
Offset/Polarity values
Offset/Polarity is not particular to a type of input or output, but the module
driver handles analog and digital (binary) inputs and outputs differently. To
set these values appropriately, you should understand how the module driver
uses them.
Offset/Polarity Notes
Analog Input (BAI)
Offset value (positive or negative) adds a fine adjustment to a
sensor reading after all scaling for calibration.
EXAMPLE If a sensor reads 74.9°F when the actual
measured value is 73.6°F, enter an Offset of –1.3 to
calibrate the sensor to the measured value.
Analog Output (BAO)
You can use the Offset value (positive or negative) to
calibrate an output, but you generally do not need to. If used,
the driver adds the offset value to the wire input value before
performing any scaling calculations to determine the ZN551's
output.
ZN551 Control Module • Rev. 3/17/2005 11 © 2005 Automated Logic Corporation