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4
Software
The DAQ units include built-in cold-junction compensation (CJC), which is
automatically invoked when you select TC measurements. The OM-DAQ-
USB-2401 automatically converts acquired voltage readings into compensated-
linearized temperature readings. This DAQ system can make thermocouple and
volts measurements concurrently.
Figure Notes: *V1 and V2 are single-ended inputs.
4.9 Measurement Duration, Scan Time, and Resolution
In relation to sampling analog input, the terms measurement duration, sample
rate, and resolution have the following meanings:
Measurement duration (per channel) – the amount of time used for sampling a
channel's input signal. The measurement durations for the OM-DAQ-USB-2401's
analog channels range from very slow (400 milliseconds for one measurement
duration) to very fast (1 millisecond for one measurement duration).
Scan Time (per scan) - The amount of time used for scanning (sampling) all
selected channels' input signal. For the OM-DAQ-USB-2401, the scan rates range
from very slow (1 hour per scan) to very fast (1 milliseconds per scan).
4-16
In DAQ applications, thermocouples should not be connected
single-ended. Doing so can result in noise and false readings.
This is especially true when acquiring other high-amplitude
signals in conjunction with thermocouple signals that are
connected single-ended.
Figure 4-26. OM-DAQ-USB-2401 Single-Ended and Differential Connections to
Analog Input Channels Diagram
*V3 is a thermocouple and is a differential input.
NOTE:
OM-DAQ-USB-2401
TERMINAL BLOCK
A
1
H
V
1
V
2
V
3+
V
3
V
3-
(PARTIAL)
A
C
A
A
1
O
2
2
L
M
H
L
COM
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