Chapter 2 — Setting Up
17
the right of the connector. The equivalent circuits of the outputs in the
two different modes is shown in
.
In the contact closure mode (link removed) the output is shorted when a
PowerChrom software method table uses a setting of Close/High. The
output relay is open when the Open/Low setting is used, and this is the
default condition.
In TTL mode (link installed) the positive output will be pulled high (about
5 V) by a resistor when the Close/High setting is used in a method
document. When the relay is shorted (Open/Low setting in software),
the positive output be at about zero volts (it will be at ground potential),
and this is the default condition. Note that in TTL mode the negative
terminal must be grounded either by using a ground reference from the
equipment it controls or by connecting it to the analog output (DAC)
ground (marked COM). This makes sure there is a solid ground from
which the output can be referenced.
Recording Unit Accuracy
PowerChrom units are factory calibrated to an accuracy of better than
0.1%. Some ‘zero drift’ or ‘gain drift’ can occur with time, however, it
is not usually necessary to recalibrate the instrument during its lifetime.
CTL Output
+5 V
Output Control signal
Output Control signal
+5 V
+ 5 V
CTL Output
+
_
Contact closure mode,
link removed
TTL mode,
link installed
Figure 2–7
The equivalent circuit of
the digital output.
