Specifications

8 – Configuring Points
128 R400
Clamp Point
When defining an analog point you can indicate whether you want the PV to be
clamped to 0% if it less than the PV clamp low limit, and 100% if it is greater than
the PV clamp high limit (for information about setting clamp limits, refer to“PV
Clamp Values for Analog Points” on page 189).
For example, because of instrumentation inaccuracies or anomalies, a controller
might give a reading of 9 units, when in fact you know that the reading should be
zero. By setting a PV clamp limit of 10, you can force the reading from the
controller to be read as zero. This can be useful for integrating a value over time.
The high and low limits for the PV clamp are defined on Station via the System
Wide Point Configuration display (see “Server-Wide Point Configuration” on
page 186 for more information).
Figure 8.6, “Effects of PV Clamping” on page 129 shows how PV clamps work.
Figure 8.5 How Drift Deadbands Work
plscpcg.book Page 128 Monday, May 28, 2001 10:11 AM