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ADU100 USB data acquisition interface
connection diagrams
 

Overview

The ADU100 features 3, ISOLATED 16-bit  analog inputs, 4 digital I/O lines, one 5 AMP relay contact output, four 16 bit event counters, and an auxiliary RS232 port. Two of the analog input lines can be programmed in 20mV to +/-2.5V ranges via an internal PGA. The third analog input is a high-level input with programmable ranges of 0-5, +/-5, 0-10, and +/-10 VDC.  Two reference outputs are available ( 2.5000V and 5.00V ) to allow direct connection of strain gauge type sensors.

Analog Connections:

The ADU100 features 3, ISOLATED 16-bit  analog inputs Labeled AN0, AN1 and AN2.

AN0 and AN1 are low level inputs that can be used as two single-ended inputs or as a single differential input for use with strain gauges or other bridge type transducers.

ADU100F4.gif (14315 bytes)FIG 1: Single-Ended Inputs

Figure 1 shows the basic connections for single ended inputs. Note that LCOM must be  connected to AGND for single ended , unipolar inputs. Single ended voltages can also be connected between AN2 and AGND.  LCOM has no function in regards to the use of AN2, the high level voltage input.

ADU100F7.gif (15276 bytes)FIG 2: Potentiometer Connection

The reference outputs can provide bias currents to allow the direct connection of potentiometers to the ADU100. Figure 2 shows how a potentiometer can be connected to the low-level inputs using the 2.5V reference output. The high level input will also accept potentiometer connections using the 5.00V output to bias the potentiometer.

ADU100F5.gif (16842 bytes)FIG 3: Bridge Connection ( 2.5V)

Figure 3 shows the basic bridge connection to the ADU100. Note that bridge excitation can be provided by the ADU100 so that no external supply is required.   In this example, the bridge excitation is 2.500V and provides the lowest noise measurement because the same voltage is used as the reference for the internal A/D converter.

ADU100F5b.gif (16802 bytes)FIG 4: Bridge Connection ( 5V )

Figure 4 shows an alternate method of connection bridge transducers where the 5.00V output is used for excitation of a strain gauge transducer.

ADU100F6.gif (14710 bytes)FIG 5: 4-20mA Current Input

Standard current inputs can be connected to the ADU100 using appropriate current loop termination resistors. In Figure 5, a 4-20mA current loop is terminated with a 125 ohm resistor which effectively converts the current to a 0.5- 2.5 Volt signal. A second resistor could be used with a second current loop and connected to AN0 in the same configuration.

 

ADU100F6b.gif (15423 bytes)FIG 6: 4-20mA Current Input (2)

The high level input AN2 can also accept current loop signals using a 250 ohm termination resistor. This converts the current to a standard 1-5V signal which can be read by the A/D converter. Both Figures 5 and 6 demonstrate how the ADU100 USB Data Acquisition Interface can be used as a low cost isolated Current loop to USB ( I/USB) converter.

IMPORTANT: Bipolar input voltages can be connected to AN2 using AGND as the reference for the input. Special considerations must be taken when using bi-polar inputs with AN0 and AN1 as these are pseudo-bipolar inputs that use LCOM as the refererence for both inputs. When bi-polar inputs are to be used with AN0 and/or AN1, NO CONNECTION can be made to AGND, AN2, or either of the 2.5V or 5V reference outputs.  Figure 7 shows how bi-polar inputs are connected to AN0 and AN1.

ADU100ff.gif (6771 bytes)

FIG 7: Bi-Polar Inputs Connections to AN0 and AN1

Digital I/O Connections:

The ADU100 features a 4-bit digital I/O port that can be configured in any combination of inputs or outputs.  When configured as outputs, the lines can sink or source up to 20mA per pin. This allows the direct connection of low-current reed relays or LED's as shown in Figure 8.

ADU100F3.gif (16793 bytes)FIG 8: Driving LED's

The digital I/O lines also feature programmable pull-up resistors to allow the connection of external contact input devices such as pushbuttons or PLC contacts. Figure 9 shows how these pull-up resistors can be used. Contact input devices are simply connected between the appropriate input and the GND pin.

ADU100F1.gif (14697 bytes)FIG 9: Contact Inputs

 

Relay Connections:

The ADU100 features a relay output rated as 5 amps AC or DC. This allows the connection of external loads such as indicator lamps, solenoids, small heaters, or other control related loads.  Figure 10 shows the connections required for a 24V indicator.

ADU100F2.gif (13665 bytes)FIG 10: Contact Output

View the complete ADU100 data sheet HERE.

    
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