2-32
|
ni.com
Chapter 2
Analog Input and Temperature Sensor Measurements
Without the AC coupling you would use the ±10 V range or the 0–10 V range. After passing
through the filter, the dynamic portion of the signal is retained and centered around 0, as shown
in Figure 2-31.
Figure 2-31.
Signal after Passing through Filter
You can now reduce your range to ±1 V to increase the resolution of the measurement.
Current Input Measurement
Some DAQ devices cannot directly measure current. This section describes how to add
components for measuring current up to 20 mA.
The conversion from current to voltage is based on Ohm’s Law, summarized by the following
equation:
V
=
I
×
R
where
V
is voltage,
I
is current, and
R
is resistance.
By putting a resistor with a known value in series with the current and measuring the voltage
produced across the resistor as shown in Figure 2-32, you can calculate the current flowing
through the circuit.
Figure 2-32.
Current-to-Voltage Electrical Circuit
0 V
Time (t)
I
R
Transducer
Input
V
in
+
–
+
–
