Power Line Rejection; Optical Isolation; A/D Conversion - Omega OM-DAQ-USB-2401 User Manual

4
Software

4.4 Power Line Rejection

The OM-DAQ-USB-2401 Series can take readings while making use of 50/60Hz
line cycle rejection. While in the line cycle rejection mode, the maximum sample
rate is as follows:
• 50 Hz rejection: Scan Rate (SR) Range: 0.153Hz < SR <= 1Hz
• 60 Hz rejection: Scan Rate (SR) Range: 1Hz < SR <= 1.667Hz

4.5 Optical Isolation

Your DAQ unit is optically isolated from its host PC by up to 500 Vdc. This
means that an inadvertent application of such voltage to the DAQ unit will
not affect the PC. In addition to isolation, the device maintains all sensitive
acquisition-related circuitry external to the PC. This physical isolation of
circuitry from the PC results in less noise and more accurate measurements.

4.6 A/D Conversion

OM-DAQ-USB-2401 uses an extremely low-noise, 24-bit analog-to-digital (A/D)
converters. They provide complete high-resolution measurement solutions for
the most demanding applications.
4-14
OMB-DAQ-USB-2401 Series Block Diagram
Power LED
Power Jack
USB
Jack
Activity LED
CJC
4
Analog Inputs
+12v
+12v output
Excitation voltage
MUX
CJC
4
Analog Inputs
+12v output
Excitation voltage
1MΩ
CJC
4
Analog Inputs
+12v
+12v output
Excitation voltage
MUX
CJC
4
Analog Inputs
+12v output
Excitation voltage
1MΩ
Figure 4-25. OM-DAQ-USB-2400 Block Diagram
Isolation
Barrier
Power Supply
Local Power
USB
Controller
Digital Isolators
Gain =
x2, 1/8
SE/
PGIA
DI
MUX
1MΩ
Gain =
x2, 1/8
SE/
PGIA
DI
1MΩ
Isolated
Power Supply
MCU
32Bit
Gain =
x1,2,4,8,16
32,64
24–Bit
PGA
A/D