UM-0085-B09
DT80 Range User Manual
Page 405
RG
command line
One or more DT80 commands typed one after the other, separated by tab, space or semi-colon characters, and
ending with a return character. Limited to a maximum of 1023 characters. For example
RA10S T 4V 5TK
is a command line made up of a schedule definition followed by three channel definitions (separated by spaces).
common-mode voltage
An unwanted AC and/or DC voltage that offsets both inputs to the DT80’s instrumentation amplifier (with respect to
amplifier ground). It is unwanted because it usually originates from nuisance sources such as electrical noise, DC
offset voltages caused by the sensors or the equipment being measured, or from ground loops.
Typically in industrial measurement, the sensor signals you apply to the DT80’s input terminals consist of
•
the small component you want to measure (a few mV to a few tens of mV), PLUS
•
a large unwanted component (a few V to a few tens of V) — the common-mode voltage.
Figure 178: Common-mode voltage VCM and Differential voltage (VDiff) – 1
When the DT80 makes a measurement, both of these components are applied to the inputs of the its
instrumentation amplifier. Then, when configured for basic (differential) use, the amplifier does two things:
•
It rejects most of the common-mode voltage (the unwanted signal). How well the amplifier does this is
indicated by its common-mode rejection ratio — see
.
•
It amplifies the difference between the signals on its two inputs. This is the wanted signal and is called the
differential voltage — see
.
Common-mode voltage is calculated as the average of the voltages between the measurement system’s ground and
the two input terminals:
Figure 179: Common-mode voltage VCM and Differential voltage (VDiff) — 2
CR
See
.
DAC
Digital-to-Analog-Converter
data acquisition system
A measurement system that scans a range of analog and digital channels, converts the readings to digital format,
and forwards the data to a host. The host does any storage or data manipulation required. See also
.
data logging system
A data acquisition system with its own on-board data storage and manipulation facilities. See also
.