ADU73 Voltage Input to USB Interface (Dual 0-5VDC)

The ADU73 Voltage Input to USB Interface enables measurement of  two 0-5VDC analog inputs, with 24-bit resolution, using a USB connection. The 5.000V reference output enables ratio-metric measurements of resistive sensors, including string pots and linear potentiometers, providing exceptional low noise 24-bit measurements.  This low-cost USB Voltage Input to USB Interface is easy to use with VB, and Visual C++ or .NET via standard HID drivers included with Windows 98,2000,XP,7,8,10,11. A mini-driver ( DLL )* is also provided allowing control using standard ASCII commands using familiar readfile, writefile commands. The ADU73 includes a 10' USB cable and is available in a flange mount enclosure with a DIN rail mount option.

Connecting external devices to the ADU73 is relatively simple, however, care should be taken when making connections to avoid measurement errors, or damage to the ADU73. The maximum current draw from the +5.00V reference output should not exceed 20mA.

1.  Connecting the ADU73 to resistive potentiometers.

Figure 1 shows the connections required to interface the ADU73 to resistive position sensing potentiometers, including linear potentiometers and string pots (draw string potentiometer). The potentiometers are biased using the +5.00V reference output to enable ratio-metric measurements.  Minimum recommended potentiometer resistance 1K ohm. Do not draw more than 20mA in total from the +5.00V reference output.

Figure1:  ADU73 connections to TE Connectivity string pot or Bourns linear motion resistive potentiometers.

2. Connecting the ADU73 to active sensors.

Active sensors can also be connected to the ADU73 with the only limitation being that a maximum of 20mA can be drawn from the +5.00VDC reference output to power the sensor.  Figure 2 shows the connections to an MPXV5050DP pressure sensor from NXP. The MPXV5050DP draws only 7mA @ 5 VDC and so two sensors can be connected safely.

Figure 2:  ADU73 connections to an active sensor (MPXV5050DP Pressure Sensor).

3. Connecting the ADU73 to thermistors.

The ADU73 can be connected to thermistors using an external bias resistor.  The external bias resistor resistance depends on both thermistor resistance, and the application requirements, and should be selected to ensure a maximum of 20mA is drawn from the +5.00V reference output.  Up to two thermistors can be connected to the ADU73.

Figure 3 :  ADU73 connections to a thermistor.

4. Connecting the ADU73 to external voltage sources.

The ADU73 can be connected to external voltage sources of up to 5VDC, including standard instrumentation 1-5VDC signals.  Note that in this configuration, the ADU73 is operating in absolute voltage measurement mode. CAUTION: No connection should be made to the +5.00V reference output when connecting external voltages.

Figure 4 :  ADU73 connection to an external voltage source.

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