4Software

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

OMB-DAQ-USB-2401 Series Block Diagram

Power LED

 

 

Isolation

 

Barrier

 

Power Supply

 

Isolated

Power Jack

Power Supply

Local Power

USB

 

Jack

 

USB

MCU

Controller

32Bit

Activity LED

 

 

Digital Isolators

CJC

4 Analog Inputs

+12v

Gain = x2, 1/8

+12v output Excitation voltage

CJC

4

Analog Inputs

MUX

 

 

SE/

 

PGIA

 

 

 

 

 

 

 

 

 

DI

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Gain =

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

x1,2,4,8,16

 

 

 

32,64

+12v output

 

Excitation voltage

1MΩ

 

CJC

 

4

 

Analog Inputs

 

+12v

 

+12v output

 

Excitation voltage

 

CJC

MUX

 

4

 

Analog Inputs

 

+12v output

 

Excitation voltage

 

 

MUX

 

PGA

 

24–Bit

 

1MΩ

 

 

A/D

 

 

 

 

 

 

 

 

 

 

 

 

 

Gain = x2, 1/8

 

 

 

 

 

SE/

 

PGIA

 

 

 

 

 

 

 

 

 

 

 

DI

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1MΩ 1MΩ

Figure 4-25. OM-DAQ-USB-2400 Block Diagram

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

4-14

the most demanding applications.

 

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Omega Engineering OM-DAQ-USB-2401 manual Power Line Rejection, Optical Isolation, A/D Conversion