Measurement-computing USB-ERB08 Manual do Utilizador descarregar pdf (Página 16)

USB-ERB08 User's Guide Functional Details

Pull-up/Pull-down switch (S2)

The Pull-up/pull-down switch (S2) sets the power-on state of each relay bank. By default, switch S2 is

configured for pull-down (relays inactive at power-up - see ). Figure 3-3

Figure 3-3. Switch S2 default configuration

PULL UPPULL DOWN

The switch labeled CL configures relays 1 through 4, the switch labeled CH configures relays 5 through 8.

 PULL UP: The relay energizes at power-up, regardless of the state of switch S1.



PULL DOWN: The relays are not energized at power-up.

Use InstaCal to read the current power-on state setting for each module group.

Screw terminals

Connect external devices to the relay contacts using the USB-ERB08 board's eight sets of screw terminals. Each

relay has a normally closed (NC), common (C), and normally open (NO) contact. shows the screw

terminals on a typical relay channel.

Figure 3-4

Figure 3-4. Typical relay channel

NC C NO

Each screw terminal is identified with a label on the board and on the underside of the enclosure lid.

Caution! Before connecting wires to the screw terminals, turn off the power to the USB-ERB08, and make

sure that the signal wires do not contain live voltages.

Wire gauge

Use 12 AWG to 22 AWG wire to connect field devices. Properly insulate the wires to avoid any short circuit to

the other connections, ground, or other points on the board.

Caution! Keep the length of stripped wire at a minimum to avoid a short to the enclosure! When

connecting your field wiring to the screw terminals, use the strip gage on the terminal strip, or strip

to 5.5 - 7.0 mm (0.215" to 0.275") long.

Daisy chaining additional relays to the USB-ERB08

Daisy chained MCC USB Series products connect to the USB bus through the high-speed hub on the USB-

ERB08. You can daisy chain a maximum of four MCC USB Series products to a single USB 2.0 port or USB

1.1 port on your computer.

MCC USB Series products are USB 1.1 full-speed devices that provide a signaling bit rate of 12 Mb/s. The

throughput rate is shared by all devices connected to the USB bus. Use the supplied cable or an equivalent cable

when daisy chaining MCC USB Series products.

To daisy chain two or more USB-ERB08 modules, follow the steps below. This procedure assumes you already

have one USB-ERB08 connected to a computer and to an external power source. The USB-ERB08 already

connected to the computer is referred to as the connected module. The USB-ERB08 you want to daisy chain to

the connected module is referred to as the new module.

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