CTI 2550-A, Installation And Operation Manual

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C T I 2550-A Installation and O peration G uide 5
Figure 5
Example of Change in Input Level
1.7.3 Example Conversion
As an example, the following figure illustrates the effects of a change in input level going from 1.25 to
2.5mV in the 0 to 5V Unipolar Input Mode. (For the 0 to 10V and 0 to 20mA Unipolar Input Modes,
or the Bipolar Modes, refer to the formulas given in Sections 1.6.1 and 1.6.2 to determine the digital
word which results from a particular input.)
1.8 Effect of Out-of-Range Input Signals
The Model 2550-A utilizes the overrange and underrange bit to indicate when a channel has reached
individual limits. The value of the overrange or underrange condition varies from channel to channel.
The reason for this is that as a channel is calibrated all of the gains and offsets and dynamic ranges of
the analog to digital converter of the system are compensated for in each analog input channel.
Therefore the point at which the analog to digital converter reaches a saturation point and can no longer
produce a change in counts for corresponding change in input signal is called the overrange or
underrange limit of the channel. This level is different for every channel. In the figures below, (sections
1.8.1 and 1.8.2), the limits for the overrange and underrange values are the minimum limits for a given
channel. The actual limits for an individual channel may be greater.