OM-WEB Series User's Guide
Signal I/O Connections
23
Figure 9. Semiconductor sensor measurement configuration
The software outputs the measurement data as a 32-bit floating point value in either voltage or temperature.
Digital I/O connections
Connect up to eight digital I/O lines to the screw terminals labeled
DIO0
to
DIO7
. Configure each digital bit for
either input or output. All digital I/O lines are connected through 47k to the
PU/D
pin, which is floating by
default. For a pull-up configuration, connect the
PU/D
terminal to the +5V terminal. For a pull-down
configuration, connect the
PU/D
terminal to the
GND
terminal.
When configuring the digital bits for input, the digital I/O terminals can detect the state of a TTL-compatible
device. The ground (
GND
) terminal provides a common ground for the digital I/O channels. Refer to the
schematic shown in Figure 10. If the switch is set to the +5V input, DIO0 reads
TRUE
(1). If the switch is
moved to GND, DIO0 reads
FALSE
(0).
Figure 10. Schematic showing switch detection by digital channel DIO0
When configuring the digital bits, use the digital logic voltage switch on the side of the device to set the voltage
to either 5 V or 3.3 V (see page 26 for more information). Refer to the digital I/O specification on page 36 for
the maximum and minimum threshold levels for each setting.
If a digital bit is set up as an alarm, that bit is configured for output and assumes the state defined by the alarm
configuration.
Caution!
The
GND
pin is isolated from the
AGND
pins and from earth ground. If a connection is made to
earth ground and
AGND
, the thermocouples are no longer isolated. In this case, thermocouples
must not be connected to any conductive surfaces that may be referenced to earth ground.
For general information regarding digital signal connections and digital I/O techniques, refer to the
OMB-DAQ-
2400, OM-USB, OM-WEB, and OM-WLS Series General Guide to Signal Connections
(available on our web
site at
www.omega.com/manuals/manualpdf/M4830.pdf
).
Configuring the DIO channels to generate alarms
The OM-WEB Series hardware features eight independent temperature alarms. All alarm options are
configurable using the web browser or InstaCal.
When a digital bit is configured as an alarm, that bit will be configured as an output and assume the state
defined by the alarm configuration. Each alarm controls an associated digital I/O channel as an alarm output.
The input to each alarm is one of the temperature input channels. You set up the temperature conditions to
activate an alarm, and the output state of the channel (active high or low) when activated. When an alarm is
enabled, its associated I/O line is set to output and driven to the appropriate state determined by the alarm
options and input temperature. Alarm configuration settings are stored in non-volatile memory and are loaded
on power up.
