Hach IO9004 User Instructions page 14

Figure 7 Externally-powered loop
1 Analog output
2 External power supply
Connect the digital outputs
Do not use the digital outputs for process control functions such as pump on/off switching or water system
shutdown. The digital output connections do not replace a PLC (programmable logic controller).
The I/O module has four digital outputs. Connect a compatible device such as a remote alarm
indicator, buzzer or PLC to the digital outputs. Refer to
Table 3 to connect the digital outputs. Refer to
specifications.
The digital outputs are independent floating switches when the PULLUP V input and associated
internal pull-up resistors are not used. The switches are normally open. The switches close when the
user-selected alarm conditions occur.
To use the optional PULLUP V input and the related internal 10 kΩ internal pull-up resistors, supply
the applicable voltage to the PULLUP V and COM (pin 14) pins. Then, connect a jumper from the
OUT # LO pin to the COM pin. The output signal logic is active low.
Pin
OUT # HI
OUT # LO
COM
PULLUP V
COM (pin 14)
Install the covers
Install the covers with the supplied hardware to keep the protection supplied by the enclosure. Refer
to Remove the covers
Connect to a flow logger or sampler
Connect the cable to a flow logger or sampler. To connect the cable to a sampler, refer to
To connect the cable to a flow logger, refer to the flow logger documentation.
5
Sets the logic high voltage for the digital outputs.
14 English
N O T I C E
Table 3 Wiring—digital outputs
on page 10. Make sure that the covers are tightly closed.
3 External device
Figure 4 on page 11,
Specifications on page 3 for the digital output
Description
Positive
Negative
Common
+25 VDC maximum
Common for PULLUP V
Figure 5 on page 12 and
5
Figure 8.