Measurement Computing SWITCH - Manual (Page 20)

20
Chapter 3
Functional Details
The Switch & Sense 8 expands the capabilities of desktop personal computers by providing SPDT relay control
and isolated inputs in a plug-and-play package. Screw terminals provide easy field wiring to the three output
lines for each of the eight onboard relays (see Figure 3 on page 22).
In addition, two terminals are provided for the differential input signals associated with each of the eight
isolated inputs.
External components
The Switch & Sense 8 has the following external components, as shown in Figure .

Direct current (dc) power connection and 9 V power supply
 External power LED
 Status LED
 USB connector /cable
Figure 2. Switch & Sense 8 rear compnents
Direct current (dc) power connector and 9 V power supply
The Switch & Sense 8 requires between 7.5 V and 20 V of external power. Your computer can configure the
Switch & Sense 8 without external power. However, external power connection is required to activate the relays
and to run tests in ICalUSB.exe.
The USB specification allows high power devices to draw up to 500 mA. When all eight relays are energized,
the collective current draw exceeds the maximum allowed for high power USB devices. Therefore, external
power is required.
Use the 9-volt (V) DC power supply cord shipped with the Switch & Sense 8 to provide external power to this
connector.