B&B Electronics 4 Channel Input Buffer Board SDAIBB Manuale Utente Scaricare il pdf (Pagina 14)

10 Chapter 1 Documentation Number UD128A8D4602 Manual

B&B Electronics Mfg Co – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104

B&B Electronics Ltd – Westlink Comm. Pk. – Oranmore, Galway, Ireland – Ph 353-91-792444 – Fax 353-91-792445

Notes on Operating Characteristics

General

• Each UD128A8D has a unique serial number. When it is installed,

it will register itself and be given a name DAQx where “x” is a

sequential number starting at 1 and increasing for each new unit

installed on that computer. Software can be written to address the

first one plugged in or by the “DAQx” name. The method is similar

to addressing COM ports, where the first one installed gets called

COM1, the next one COM2, etc. The uninstall should take out all

instances, so the next one plugged in after an uninstall, and new

install, will be named DAQ1.

• The UD128A8D enumerates as a full powered device, which

means it will request as much as 500mA from the USB bus. For full

operation it must be connected into the host or a externally

powered hub which has a power supply.

• If you want to trigger on a digital input or analog input value your

software must read and act on the value. There are no hardware

triggers built in.

Analog Inputs

• A zero voltage input (Input grounded) produces a reading of 5 or 6

LSbits (6 or 7mV). The input buffer does not allow the input to go

any lower than this.

• All unused inputs should be grounded.

• Maximum sampling rates will be best when this is the only device

on the USB. It may be necessary to add a USB controller rather

than a hub to maintain throughput.

• A capacitor of 0.1 to 1uF works well as a low pass filter for slow

signals that may be noisy or some distance from the UD128A8D.

• There is no isolation in the device. Ground noise and grounding

differences should be kept to a minimum.

• Timed sampling takes place in sequential order as close together

as possible. The time between samples for each channel should

remain constant. The analog channels go through a multiplexer

which selects each channel.

• The Analog Input reference is set to 5V, but can be overdriven by

an external reference. (See Fig. 2.19)

The analog inputs are capable of being configured as differential pairs,

but have some rules.

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B&B Electronics 4 Channel Input Buffer Board SDAIBB Manuale Utente Pagina 14