SeaLevel DIO-16.PCI User Manual page 9

0) by the PC. When the input signal is too low to turn on the opto-isolator, the output goes high, and the port
bit is read by the PC as a high logic level (binary 1).
The input impedance of each isolated input is approximately 560 ohms (factory default). The opto-isolator
requires approximately 3mA to turn on. The maximum input current is 50mA. There are two things to
consider when selecting the input resistor. The first is turn on voltage for the circuit to sense, and second
is the maximum input voltage. Maximum input voltage must not provide too much power to the input
resistor and must also not overdrive the opto-isolator input current specification. The following formulas
apply:
The following table shows common input resistors and the ranges associated with each.
Input Resistor
The turn-off voltage for all resistors is less than 1V.
Increasing the input resistor accordingly can increase the maximum input voltage. Because socketed DIP
resistors are utilized, they can easily be replaced with a different value. Sealevel, if necessary, can do this.
The input circuits are not intended for monitoring 120-volt AC circuits. In addition to being too high
a voltage for the circuits, it is dangerous to have that high a voltage on the card.
© Sealevel Systems, Inc. 8002 Manual | SL9021 10/2022
Turn on Voltage = diode drop + (turn on current) x (resistance) [Ex: 1.1 + (.003) x R]
Input Current = ((input voltage)-1.1V) / (resistor value)
Maximum voltage = 1.1 + square root of (.25(resistor value))
Turn-On
220W 1.8V
560W 2.8V
1KW 4.1V
2.2KW 7.7V
3.3KW 10.0V
4.7KW 15.2V
Input Range Max Input
1.8 – 7.0V 8.5V
2.8 – 10.6V 12.9V
4.1 – 13.8V 16.9V
7.7 – 20.0V 24.5V
10.0 – 24.0V 30.0V
15.2 – 28.0V 35.0V
Max Current
27mA
20mA
15mA
10mA
9mA
7mA
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