B&B Electronics 4 Channel Input Buffer Board SDAIBB Manual do Utilizador descarregar pdf (Página 16)

12 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

Digital I/O

• The digital reference is intended primarily for pull-ups on the digital

lines. Current output is limited by a series resistor, so little external

circuitry can be powered. Because it is connects to all the digital

circuitry, it’s a bad idea to use it for any analog input signal

conditioning.

• Digital channels have to be polled. Polling speed depends on the

PC speed, OS, and what other apps are running. Our tests here

indicate a 4-8 millisecond polling interval. If you need to catch a

shorter period signal, you must add external latch circuitry.

Calibration

• Input or outputs should not be calibrated exactly at the rails (0V, 5V)

one diode drop below the rails is easy to achieve and provides a fairly

stable voltage.

• Input and output calibration values can most easily be determined by

connecting one of the D/A outputs into one of the A/D inputs to

compare input & output readings with your standard.

• Wait for calibration voltage to stabilize.

• Make sure calibration is at operating temperature.

• Make sure to ground any unused inputs.

• Make sure to read calibration voltage with UD128A8D connected.

• The more accurate the calibration test equipment the better.

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