Unipolar / Bipolar Input

For analog input systems, there are two types of inputs: unipolar and bipolar.

Unipolar inputs
Unipolar signals swing from zero to positive full-scale, thus having only a positive polarity. With the single-ended analog input of an ADC, the input ranges from zero-scale (typically ground) to full-scale (typically the reference voltage). For a unipolar ADC with differential inputs, the positive input swings from zero-scale (the negative input) to positive full-scale (with respect to the negative input).

Bipolar inputs
The term "bipolar" indicates that the signal swings above and below some reference point. In single-ended systems, the input is typically referenced to analog ground, so a bipolar signal refers to one that swings above and below ground. In differential systems, where the signal is not referenced to ground but where the positive input is referenced to the negative input, a bipolar signal is one in which the positive input swings both above and below the negative input, which is not necessarily analog ground.

The following chart shows the relationship between input range and resolution for a 16-bit AI channel. The unit resolution will get higher when the input range gets wider. With both unipolar and bipolar available, users have more and more flexibility to fit their own applications.

Most of Advantech’s data acquisition cards support both unipolar and bipolar inputs.

Supporting cards for PCI bus:
PCI-1710 series, PCI-1712, PCI-1713, PCI-1716, PCI-1718 series, PCI-1741U,
PCI-1747U, etc.
Supporting cards for ISA bus:
PCL-816, PCL-818H, PCL-818HD, PCL-818HG, PCL-813B, etc

Advantech Industrial Automation

ADVANTECH Automation 1320 Kemper Meadow Dr., Ste 500, Cincinnati, OH 45240. 877-294-8989
Copyright 2005 Advantech Automation Corporation. All Rights Reserved