User Manual

RedLab 1208LS User's Guide Functional Details

For example, the RedLab 1208LS exhibits a typical calibrated gain error of ±0.2% on all ranges. For the ±10 V

range, this would yield 10 V × ±0.002 = ±20 mV. This means that at full scale, neglecting the effect of offset for

the moment, the measurement would be within 20 mV of the actual value. Note that gain error is expressed as a

ratio. Values near ±FS are more affected from an absolute voltage standpoint than are values near mid-scale,

which see little or no voltage error.

Combining these two error sources in Figure 14, we have a plot of the error band of the RedLab 1208LS for the

±10 V range. This is a graphical version of the typical accuracy specification of the product.

The accuracy plots in Figure 14 are drawn for clarity and are not drawn to scale

-FS

+FS

Inp ut Vo lta g e

4095

9.77mV

2048

Output Code

Idea l

Idea l + 9.77m V + 20 m

Ideal -(9.77mV + 20 m V)

Id e a l -(9.77m V + 20 m V)

Ide a l

Ideal + 9.77mV + 20 mV

Figure 14. Error band plot

RedLab 1208LS channel gain queue feature

The RedLab 1208LS's channel gain queue feature allows you to set up a scan sequence with a unique per-

channel gain setting and channel sequence.

The channel gain queue feature removes the restriction of using an ascending channel sequence at a fixed gain.

This feature creates a channel list which is written to local memory on the RedLab 1208LS. The channel list is

made up of a channel number and range setting. An example of a four-element list is shown in the table below.

Sample channel gain queue list

Element Channel Range

0 CH0 BIP10V

1 CH0 BIP5V

2 CH7 BIP10V

3 CH2 BIP1V

When a scan begins with the gain queue enabled, the RedLab 1208LS reads the first element, sets the

appropriate channel number and range, and then acquires a sample. The properties of the next element are then

retrieved, and another sample is acquired. This sequence continues until all elements in the gain queue have

been selected. When the end of the channel list is detected, the sequence returns to the first element in the list.

This sequence repeats until the specified number of samples is gathered. You must carefully match the gain to

the expected voltage range on the associated channel—otherwise, an over range condition can occur. Although