Dwyer DL8 - Manual (Page 10)

This value will be needed when it comes time to create your
own custom equation using Trendreader Software’s Expert,
Equations function.
You can also easily convert the 10V channel to measure 0
to 100 mA current simply by putting a 100 ohm resistor
(minimum rating: 2 watts) between the “10V” and
“-Common” terminals.
5 Volt Channels
The two 5 volt channels can be modified to span higher
ranges (greater than 5V DC) by adding a single resistor, in
the same way as shown for the 10V channel in Figure 8, to
either, or both, of the two “5V” terminals. The value of the
resistor R must be calculated by the following equation
based on the desired voltage input range Ein:
R = (4,000 x E
in
) - 20,000
For example, if you wish to measure up to 20 volts, the
resistor value should be:
Since you won’t be able to get the exact resistor value that
you calculated, you can determine the actual input range
you’ll have by plugging the value of the resistor back into
the formula:
You can easily convert either of both 5V channels to mea-
sure 0 to 50 mA current by wiring a 100 ohm resistor (min-
imum rating: 0.5 watts) from the “5V” terminals to common.
2.5 Volt Channel
The 2.5 volt channel can be modified to span higher ranges
(greater than 2.5V DC) by adding two resistors to the input
terminals as shown in Figure 9. The value of the resistor
marked “10K” must be 10,000 ohms ±1%. The value of the
resistor marked “R” must be calculated by the following
equation based on the desired voltage input range (E
in
):
R = (4,000 x E
in
) - 10,000
For example, if you wish to measure up to 20 Volts, the
resistor value should be:
(4,000 x 20) - 10,000 = 70,000 ohms.
Since you won’t always be able to get the exact resistor
value that you calculated, you can determine the actual
input range you’ll have by plugging the value of the resistor
back into the formula:
This value will be needed when it comes time to create your
own custom equation using Trendreader software’s Expert,
Equations function.
You can easily convert the 2.5V channel to measure 0 to 25
mA current by wiring a 100 ohm resistor from the “2.5V” ter-
minal to common.
200 millivolt Channel
The 200 millivolt channel can be modified to span higher
ranges (greater than 200 mV DC) by also adding two resis-
tors, in the same way as shown for the 2.5V channel in
Figure 9. The value of the resistor marked “10K” must be
10,000 ohms ±1%. The value of the resistor marked “R”
must be calculated by the following formula based on the
desired voltage input range (E
in
):
R = (50,000 x E
in
) - 10,000
You can also modify the 200mV channel to log current loop
signals with greater sensitivity than the two 25 mA chan-
nels. To do this, put a 100 ohm resistor across the “200mV”
and “-Common” terminals and you will be able to log cur-
rents from 0 to 2.0 mA with approximately ten times the res-
olution of the 25mA channels. The equation to use to
determine other current (I
in
) ranges, in milliamps is:
E
in
= R + 10,000
4,000
E in =
R + 20,000
4,000
200
I
in
S =
Figure 8: Modifying the 10 volt channel for extended range
Figure 9: Modifying the 2.5 volt channel
(4,000 x 20) - 20,000 = 60,000 ohms.
Bulletin E-90-DL8 6/22/05 3:56 PM Page 10