Computed Channels; Mx+B Scaling; Analog Channels - Fluke 2680A User Manual

Computed Channels

In addition to the analog channels, the instrument provides an additional 60
computed channels by processing analog channels and other computed channels.
The computed channels are numbered 901 to 960. The following calculations are
used:
•
The average of a group of channels,
•
The difference between any two channels,
•
The difference between a channel and the average of a group of channels,
•
A mathematical equation. Other channels, time and totalizer can be part of the
equation.
For computed channels, the functions use 24 bits and an exponent for calculations.
As a result, when the totalizer or time exceed 16,777,215 units, the number will be
rounded off to remain within the 24 bits. For example, one count more than
16,777,215 would be rounded to 16,777,220 in a computed channel.

Mx+B Scaling

Mx+B scaling multiplies a measurement by a multiplier M and then offsets it by
an offset B. For example, Mx+B scaling of 100x+50 applied to a measured or
computed channel value of 1.15 results in a reading of 100(1.15)+50=165. A
common use of Mx+B scaling is to scale a sensor or transducer to provide for
display and recording in engineering units. The Mx+B annunciator lights when a
monitored channel has scaling applied.

Analog Channels

The analog channel measurement connections are made via the Universal Input
Modules. External signal conditioning for the analog inputs is not necessary for
most common electrical signals. The input channels are numbered 101 to 120, 201
to 220, 301 to 320, 401 to 420, 501 to 520, and 601 to 620. The host computer
configures all analog channels using the Fluke DAQ software.
There are two different analog modules available for the 2680 Series instruments
with up to 6 modules for any given instrument. Each module is isolated from every
other module to 300 V. One analog module is the fast analog module (FAI) and
has a maximum rate of 667 channel readings per second but a limited input voltage
of 50 V dc or 30 V rms. The other analog module is the precision analog module
(PAI). The PAI has a maximum of 300 V dc rms (on channel 1 and 11) and a
maximum rate of 133 channel readings per second. All other channels are 150 V
maximum for the PAI module. The Digital IO/Relay and Totalizer module can
monitor digital type (High or Low) signals.
Instrument Features and Capabilities
Overview
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