User's Manual

Glossary

frame Sequence of bytes sent from a computer to a device or vice versa. The

syntax of the frame depends on the protocol being used. A read frame

contains enough information to specify a set of variables whose values

the device should return. A write frame specifies a variable in the device

and a new value to write into that variable. Some protocols support the

writing of multiple variables in a single frame. A response frame is

returned from the device to the computer, indicating whether the frame

just sent to it was received successfully. If the frame just received was

a read frame, the response frame contains a set of requested values.

hi and hihi Alarm settings. Both warn that a value has gone above some setpoint.

Generally a Hi alarm is used to alert an operator of a need for intervention.

A hihi alarm is usually used to alert an operator that the value has been

exceeded by an even greater margin than a hi alarm indicates, and is usually

used to indicate an urgent need for action.

historical logging The process of storing data in a database for use at another time, or from

another location.

HOA Hand-Off-Auto control, used to set whether a value must be changed

manually, is completely turned off, or functions automatically. You can use

a Pot object and a complex expression to create this sort of control in

Lookout, or you can use a RadioButton object, depending on the particular

requirements of the task you need to accomplish.

I/O point Every read-only, write-only, or read-write connection Lookout makes to

external hardware is counted as an I/O point. Lookout is licensed for use

with a set number of I/O points. If you exceed the number you are licensed

to use with your copy of Lookout, a warning message appears on your

computer screen warning you to shut down one of your processes within a

specified time before Lookout cuts back on I/O usage.