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DAQ channel assignments

Many sensors (often, pressure gauges) can deliver an output signal greater than 10 volts. Such voltages overload the DAQ's internal circuitry, preventing it from making reliable measurements. Other signals are affected, too, not just the ones with excessive signal voltages. The problem can be circumvented by inserting a voltage divider circuit between the device and the DAQ, to reduce the excessive output signal to below 10 volts. Aeon's HACS-DAQ interface contains voltage dividers for this purpose.

It is best to reduce the output signal as little as possible, because the accuracy and precision of the sensed value are reduced along with the signal level. This requires selecting the divider based on the true maximum output voltage of each device.

The "true maximum output voltage" of a device is not specified or published by the manufacturer. It must be measured, with the device powered and in a condition that will produce its highest output voltage. (E.g., when testing a pressure sensor, make certain that it is exposed to a pressure at least as great as the highest pressure it will encounter in normal operation.)

Once a device has been measured, select a HACS-DAQ channel with a maximum allowable input exceeding the device's true maximum output voltage.
Channels 0 and 1 can accept signal voltages up to +15 VDC.
Channels 2-9 can accept up to +12.25 VDC.
Devices connected to the remaining channels must have maximum output voltages below 10 VDC.

ChannelDevice Power VDCOUTNotes
0-1+15+15 VDC maximum input
2-9+15+12.25 VDC maximum input
96-103+15+10 VDC max
104(+5)use for MainsDetect only; no divisor installed
  leave VDCOUT disconnected
111+5VDCOUT jumper to power higher channels
112-123+5no divisors or filters on ch >= 112
124(+5)GND (jumper input to GND)
  leave VDCOUT disconnected
125+5(internal Ambient temperature)
126+5(internal Ambient pressure)
127+5(internal 5V power monitor)
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