3B Scientific 3B NETlab™ - Manual (Page 6)

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or more digital inputs (A, B), (A, B, C), (A, B, C,
D) or either of the analog inputs. If the analog
inputs are selected, an additional check box
appears for setting a comparator threshold
(see below).
• Input range:
Digital inputs: assigns logical states to physical
input signals. “Uninterrupted = 1” means that
high voltage (>3.8 V) at the input corresponds
to a logical 1 and low voltage at the input
(<0.3 V) corresponds to a logical 0. The relation
is reversed if “Uninterrupted = 0”. This nota-
tion is derived from the status of a light barrier
associated with the digital input.
Analog inputs: (see above)
• Comp. level: sets a threshold voltage, specified
as a percentage of the upper limit of the input
range. The threshold voltage denotes the point
of transition between the two logical states.
By using the data conversion table on the right
hand side, it is possible to define how you want a
value to be displayed in relation to the actual sig-
nal. This relation is described by means of a table
consisting of pairs of values. Enter pairs of values
for the measured value and the value to be dis-
played starting from the bottom and working up.
Enter the unit for the new value in the “Results”
box. During subsequent measurements, instead of
the directly measured value the value displayed
will be converted with the help of the table. Values
between the entries in the table will be interpo-
lated assuming a linear gradient between entries.
5.1.3 Formulas:
Underneath the input control panel is another
panel in which it is possible to enter formulae that
are based on the measured values. This function is
mostly used when the values of a particular quan-
tity are to be displayed together with the measured
values. The quantity to be displayed is a function of
the measured quantity, i.e. its values can be calcu-
lated directly from the measurements.
• In order to enter a new formula, select “(New
Formula)” from the list and click “Edit”. .
• In the dialog box which appears, enter the
name of the value to be calculated in the
“Formula name” field and the corresponding
unit in “Formula unit”.
• To define the formula, use variables and func-
tions from the two lists that are provided by
double clicking the “Formula text” field. Note:
the term representing the measured values is
entered in the formula in inverted commas.
The check box “Use prefix” makes it possible to
display formula values using prefices instead of
expressing them in powers of 10.
After clicking “OK” to confirm the entries, the for-
mula name is added to the list. When this is se-
lected, the formula can be edited or deleted by
means of the corresponding buttons.
5.1.4 Control of measurements:
After selecting inputs and entering formulae, click
“Inputs OK” on the input control panel to confirm
the entries. You can now proceed with adjusting
settings for recording measurements via the control
panel underneath (Measurement control panel).
Various logging/recording modes can be imple-
mented depending on the selection and configura-
tion of the inputs. First of all, however, it is impor-
tant to define the recording speed (sampling rate)
in the field “Sampling rate”. The entries set the
interval between two recordings or, in some cases,
the corresponding frequency. AC current or voltage
measurements, i.e. measurements of root mean
square values, or measurements involving several
sensors can only be carried out in a slow mode
(interval > 0.5 s).
The final option is for manual mode (“manual
sampling”), in which recording of a measurement
is triggered by clicking a button.
The following three recording modes are available:
Recorder: a pre-defined number of measurements
are carried out. This number can be specified di-
rectly via the field “Number of measurements” or
indirectly via the duration of the measurement (set
using the adjacent “…” button). At a sampling rate
of 100 Hz or less, the measured values are output
in real time as the measurements are made. In
high-speed mode (>100 Hz), the data is first stored
in the internal memory of the equipment and read
out after measurements have been completed. It is
possible to view the measured values in various
ways, e.g. as a graph or in tabular form.
Oscillosc.: the measurements are recorded over
time and displayed as a curve. After each sweep
from left to right, the old curve is replaced by a
new one. Unlike standard mode, in oscilloscope
mode only the last 128 measurements can be
viewed or stored. Since a new trace is recorded only
a few times per second, at high-speeds oscilloscope
mode only displays samples of the overall signal
waveform. However, the advantage over standard
mode is that, even in high-speed mode, it is possi-
ble to observe measurements in “real time”.
Datalogger: it is also possible to record measure-
ments offline using 3B NETlog™, without being
connected to the computer. The necessary configu-
ration can be selected on the equipment itself or
conveniently using this function in 3B NETlab™.
After completing measurements, once the device is
connected to the computer again, the data can be
read out via the same function.
Use the “Trigger” button to open a dialog box that
defines the trigger conditions that initiate re-
cording in standard mode.