Omega OMB-DAQBOARD-500 Series, Руководство пользователя

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2-10 Connections & Pinouts
887293
DaqBoard/500 Series User’s Manual
Differential for Floating Signal Sources
Floating Signal Sources are typically wired to a data acquisition board in Single-Ended configuration. However,
when the Floating Source signal leads pass through an electrically noisy environment, Differential configuration
will give the best performance.
When wiring Floating Signal sources in Differential configuration, a resistor can be connected from the low side of
the sources to analog ground (AGND). These resistors create a return path to AGND for the bias currents of the
instrumentation amplifier and can reduce the common mode noise.
All DaqBoard/500 Series boards provide 10 M
Ω
of resistance between each analog input and ground.
In most cases the 10 M
Ω
of resistance is sufficient for the return of bias current .
Resistor Connection Scenarios
If the Input Signal is
DC Coupled If the Input Signal is AC Coupled
Use a Resistor Value from: 10 K
Ω
to 100 K
Ω
Use resistors with values from: 10 K
Ω
to 100 K
Ω
Connect the resistor between: (a) Connect one resistor between:
Input Signal Return (ARET) and AGND Input Signal High and Input Signal Low
(b) Connect a second resistor between:
Input Signal Low and AGND
Making resistor connections as indicated will significantly increase the load on the measurement source, possibly
reducing the measured voltage. A trial and error approach may be required when trying to reduce common mode
noise.
The following figure shows how to properly wire a Floating Source Signal in Differential configuration.
Differential Configuration for Floating Sources