MSI-9000 CellScale
®
System • 3750CS User Guide Page 57
MEASUREMENT SYSTEMS INTERNATIONAL
Software V1-15 to 1-20
Figure 4
Figure 5
Programmable Logic Controllers (PLCs) are in common use for machinery control. The 3750 can interface
to PLCs with the relay outputs or with the logic output on set point 8. Figure 6 shows one possible way of
interfacing to a PLC. More sophisticated PLCs are able to take data directly from RS-232 and integrate the data
into the control process. See the RS-232 option section for details.
Figure 6
Logic Output (Set Point 8)
Set Point 8 is unique from Set Points 1-7. The output consists of a logic output capable of driving standard TTL
loads. As the output is in reality 4000B series CMOS devices, it may be necessary to provide an external pull-up
resistor in certain cases. Values of 1k
Ω
to 4.7k
Ω
usually will suffice. There are two complementary outputs as
shown in Figure 7. The TTL Hi output goes high when the set point is tripped. The TTL Low output goes low