Reference
Analog Terminal Board
e)
Provision for LED indication of TTL digital line levels.
f)
Provision for cold junction compensation circuitry, CJC, for
thermocouple inputs. ATB-CJC version only!
Fused Power Rails.
_________________
The +12Volt and -12Volt power lines are lead via 62mA
fuses to the 2nd terminal of the Digital i/o port rails.
It is recommended that not more than 50 mA is drawn
from the PC! Earlier style PC’s may have a low wattage
power supply and therefore LESS power should be drawn
from these type of PC’s.
Attaching The Optional LED’s.
___________________________
Each of the 16 digital i/o signal lines of the ATB can have
an optional LED and current limiting attached, this can be used
as an onboard indicator of the signal logic level. Depending on
the circuits connected to these lines it may not be appropriate to
have an LED and resistor attached so this is an optional, user
fitted feature. The current limiting resistor is nominally 470
Ohm, though anything in the range 100 Ohm to 1k Ohm will
work.
Figure 1-1. Optional LED.
_______________________
Attach the led’s and resistor
to required screw terminals.
Care should be taken to ensure
that the LED is connected the
correct way round, long leg is
the Anode, and that the ATB
is disconnected from both the
PC and any user circuitry that
is powered up!
Only connect an LED if the current taken by the resistor and
LED will not effect the rest of the circuit to that terminal line.!
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