Data Translation DT3000 Series, Руководство пользователя, Страница: 72 / 156

Principles of Operation
71
For each channel, choose the gain that has the smallest effective range that includes the signal
you want to measure. For example, if the range of your analog input signal on a DT3001 board
is ±1.5 V, specify a range of –10 V to +10 V for the board and use a gain of 4 for the channel; the
effective input range for this channel is then ±2.5 V, which provides the best sampling
accuracy for that channel.
The way you specify gain depends on how you specified the channels, as described in the
following subsections.
Specifying the Gain for a Single Channel
The simplest way to specify gain for a single channel is to specify the gain for a single-value
analog input operation using software; refer to
page 73 for more information on single-value
operations.
Specifying the Gain for One or More Channels
For DT3000 Series boards, you can use software to specify the gain for each analog input
channel entry in the analog input channel list.
A/D Sample Clock Sources
DT3000 Series boards provide two clock sources for pacing analog input operations in
continuous mode:
• An internal A/D sample clock that uses the 16-bit A/D Counter (with a 4-bit prescaler) on
the board
• An external A/D sample clock that you can connect to the screw terminal panel
The A/D sample clock paces the acquisition of each channel in the channel list; this clock is
also called the A/D pacer clock.
The following subsections describe the internal and external A/D sample clocks in more
detail.
Table 4: Gains and Effective Ranges
Gain
Bipolar Analog
Input Range Gain
Bipolar Analog
Input Range
1 ±10 V 1 ±10 V
2 ±5 V 10 ±1 V
4 ±2.5 V 100 ±0.1 V
8 ±1.25 V 500 ±0.02 V
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