DI-500/510 Series and DI-750/760 Series Hardware Manual
Getting Started
7
against the signal wire and not the wire insulation. Do not overtighten; and (3) Tug gently on the signal lead to ensure
that it is firmly secured.
Analog Inputs
DI-500/510 and DI-750/760 Series instruments may be configured to connect 16, 32, 48, or 64 (model dependent)
differential analog channels (expandable to 240 channels with optional expansion instruments). Analog signals may
be connected to the banana jacks or to the screw terminal connectors. The high level analog inputs are intended for a
full scale measurement range of ±10V; signal-conditioned inputs are intended for a full scale measurement range of
±5V (if 5B module socket is bypassed - otherwise the full scale measurement range is determined by the 5B module).
The maximum input voltage without damage is 30V.
When needed, per-channel transducer excitation is built-in (5B module dependent), eliminating the need for external
power supplies.
Connecting a Differential Amplifier
Differential inputs allow the DI-500/510 or DI-750/760 Series amplifier to detect the difference in voltage between
the high (+) and low (-) inputs. Differential amplifiers have the advantage of reducing common mode voltages (i.e.,
those appearing simultaneously and in phase on both inputs). This capability may be leveraged to great advantage to
reduce noise riding on a signal of interest.
Two signal measurement conditions govern configuration of a differential channel input: (1) The signal to be mea-
sured is ground-referenced; or (2) the signal to be measured is isolated from ground. The signal that is isolated from
ground requires no special consideration when connecting to a differential amplifier, however the ground referenced
signal does.
Ground-referenced Signal Sources
A ground-referenced signal source is one with a local ground that may not be (and probably is not) at the same poten-
tial as the computer's ground. This potential difference between signal and computer ground is referred to as a com-
mon mode voltage and is caused by a number of different factors.
The most common of these is different physical locations of the computer and signal ground points. Since wire is not
a perfect conductor (i.e., exhibiting zero resistance regardless of length) a voltage drop, however small, will always
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Free Datasheet http://www.datasheet4u.com/
