Page 6-4
IsoAir 310P Aerosol Particle Sensor Operations Manual
Chapter 6 4-20 mA Input and Solid State Outputs
Analog Inputs: Connections and Configuration
Resolution
: Assume a sensor outputs an analog range from 0 – 10 volts. The IsoAir
310P has a
Resolution
of 12 bits, so the smallest divisible voltage for the 0 – 10 voltage
output is (10 – 0) / (4096) → (10) / (4096) = 2.44 millivolts. The value 4096 is used for
resolution because 0 is a value, and the instrument will discriminate between changes
of 2.44 mV.
Offset
=
Minimum
- (Scale *
RawData Min
)
Example: Using the same temperature sensor from previous examples:
Range = 152 (measurements from -32 – 120° F)
Scale:
9.5 (if using 4 – 20 mA current)
0.037 (if using 0 – 10 volts)
Offset:
Current = (-32) – (9.5 * 4) → (-32) – (38) = -70
Voltage = (-32) – (0.037 * 0) → (-32) – (0) = -32
Facility Net adjustment of the Scale and Offset values is performed in the Analog
Sensors tab during IsoAir 310P instrument configuration.
Figure 6-2
Facility Net Analog Configuration
For the Units column, “deg C” or “deg F” are recommended values for the Temperature
analog input, and “%RH” for the Relative Humidity analog input.
NOTE:
If the Scale and Offset numeric values are correctly entered, and
Facility Net reports those numeric values, the wiring is not correct, the
probe is defective, or the PCB inside the IsoAir 310P is defective or is
unplugged. Check all the connections inside the box.
