Analog Inputs: Connections and Configuration
Chapter 6 4-20 mA Input and Solid State Outputs
IsoAir 310P Aerosol Particle Sensor Operations Manual
Page 6-3
Configuration
When connecting the IsoAir 310P to Facility Net software, the Scale and Offset values
must be entered. Different Analog Output sensors can output values in current or
voltage, typically 4 – 20 mA or 0 – 10 volts. The Scale and Offsets must be calculated for
the specific operation (e.g. voltage or current), and these values are entered in the
Analog Input tab.
Range
= the sensor’s
Maximum
value – the sensor’s
Minimum
value
Example: A Temperature sensor that measures from -32 to 120° F
Range = (120 – (-32)) = 152
Scale
= (
Maximum
-
Minimum
) / (
RawData Max
-
RawData Min
)
where
Maximum
and
Minimum
is the working Range of the sensor
RawData Max
and
RawData Min
is
the range of current or voltage
The equation simplifies to:
Scale
= (Sensor’s Measurement Range) / (Sensor’s Output Range)
Analog Sensors that Output Current
: Most common is 4-20 mA operation, so in terms
of 4-20 mA electrical Current, the
RawData Max
is 20 and the
RawData Min
is 4.
Example: Using the temperature sensor above, the Range is 152.
Scale = (152) / (20 – 4) → (152) / (16) = 9.5
Analog Sensors that Output Voltage
: In terms of voltage, the IsoAir 310P uses a 12-
bit Analog-to-Digital Converter (ADC). Consequently, if the Analog sensor operates on
differences in voltage—and not current—the
Resolution
must be considered.
The resolution (discrete voltage values) for a 12-bit ADC is 4096. The
RawDataMax
is
4095 and the
RawDataMin
is 0 (a discrete value).
Example: Using the previous temperature sensor, the Range is 152.
Scale: (152) / (4095 – 0) → (152) / (4095) = 0.037
