User`s guide

ACLD-9182A • 11
2.3.2 Adjust Threshold for Isolated Mode
The input isolated mode of the ACLD-9182A is actually driven by current
instead of voltage level. The logic low means the input leakage current
should be less than 1mA, otherwise the input status will be treated as
logic High (1).
To avoid the logic high voltage as low, the ACLD-9182A is equipped with
a variable resistor VR1, which is used to adjust the threshold level for all
the 16 isolated input channels.
DIn+
DIn-
RV
4K +5V
Adjusting procedures:
1 Apply a +5V voltage source at DIH and DIL along with a 4K Ohms
resistor. The resistor limits input current to about 1mA.
2 Adjust the VR1 until the LED0 is off.
Follow the adjusting procedures, if channel 0's input voltage is low, and
the input leakage current is less than 1mA, the input status is considered
as logical low (TTL 0). To prevent higher input leakage current, you can
change the 3.9K Ohms resistor by a lower one, and use the above
procedures to meet your requirements.
2.3.3 Customize the Current Limit Resistor
The default voltage input range of the ACLD-9182A is from 0V to 24V. To
accept higher voltage input, you should replace the current limit resistor,
RA0...RA15, for each channel.
The current rating of the 4N35 photocoupler is about 60mA. It is
recommended that the input current is within 20mA. If you want to
choose the proper current limit resistor, please use the following formula
to calculate the input current( IF).
Vin = IF X Ri
Pw = Vin X IF