Section 6
6-8
Interfacing
corresponds to zero volts (or 4mA), and the source channel value which
corresponds to full scale voltage (or 20mA).
For example, to configure DAC #1 to output a voltage signal proportional to
differential CO
2
, 100
µ
mol/mol full scale, press FCT 05 and set
DAC 1 Code = 23
(Differential CO
2
channel)
1 0V
→
0
(X
o
, zero volts corresponds to 0
µ
mol/mole)
1 5V
→
100
(X
F
, full scale corresponds to 100
µ
mol/mole)
When a voltage range R is selected, the DAC output voltage V resulting
from a CO
2
differential X is given by
V
R
X X
X
X
o
F
o
=
−
−
where R = 5V or 100mV. If the 4 to 20mA current loop is selected, the
output current I (milliamps) is
I
X X
X
X
o
F
o
=
−
−
16
To convert the DAC voltage output signal to
µ
mol/mol (or other units),
X
X
X
R
V X
F
o
o
=
−
+
For the 4 to 20mA channel,
X
X
X
I
X
F
o
o
=
−
−
(
)
+
16
4
or, in terms of a slope and offset,
X
X
X
I
X
X
F
o
o
F
=
−
+
−
16
5
4
