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2 PURPOSE AND CHARACTERISTICS
Cobra4 Sensor-Unit Energy serves to measure and directly
display dimensions of electric power and energy in direct and
alternating current circuits (current, voltage, reactive power,
real power and apparent power, phase shift, frequency, elec-
tric work).
Three measurement modes are offered: “u(t), i(t)”, “Energy
DC” and “Energy AC”.
According to the application, Cobra4 Sensor-Unit Energy can
be connected to any one of the following measured data re-
cording instruments for data transmission to it;
•to Cobra4 Wireless-Link (12601-00) for wireless trans-
mission of data to a computer,
•to Cobra4 USB-Link (12610-00) for wireless transmis-
sion of data to a computer via a USB-cable,
•to Cobra4 Junior-Link (12615-00) also for wireless
transmission of data to a computer via a USB-cable,
•to a hand-held Cobra4 Mobile-Link (12620-00).
The ports for the measured data recording instruments are
on the front of the Sensor-Unit, whereby mechanically secure
locking in position is ensured by the hole and engaging
mushroom combination.
The measurement inputs for current and voltage are on the
top side of the Sensor-Unit. These inputs are galvanically
separated.
Instantaneous values of current and voltage can be meas-
ured in the “u(t), i(t)” measurement mode. In “Energy DC” and
“Energy AC” modes, and supplementary to current and volt-
age measurement, a microcontroller directly calculates de-
rived electric dimensions from measured values and makes
their values directly available as live measured values. Real
effective values (true RMS) are measured in particular in
“Energy AC” mode.
The Sensor-Unit is protected against overvoltage and over-
current (see Technical specifications). It even holds up to the
short-circuit currents of student power supply 13505-93 and
universal power supply 13500-93 which are above the maxi-
mum overcurrent specified for the Sensor-Unit.
This is important, as short circuit currents are frequently
above stated maximum current values for power supplies.
3 FUNCTIONAL AND OPERATING ELEMENTS
3.1 Operating elements
Cobra4 Sensor-Unit Energy has no manual operating ele-
ments. Operation of it is either via the Cobra4 Mobile-Link
hand-held measuring instrument , or via a computer to which
a Cobra4 USB-Link, Cobra4 Junior-Link or Cobra4 Wireless-
Link has been connected, and is possible as soon as the
connection between the Sensor-Unit and one of the three
measured data recording instruments has been made.
3.2 Functional elements
Cobra4 Sensor-Unit Energy has one voltage input and two
current inputs. The current inputs are to be switched accord-
ing to the measuring range. Please note here that the greater
measuring range must always be used to start with. This is
necessary to avoid faulty functioning.
Sensor-Unit Energy is designed so that it can be installed as
a fixed part of a circuit in which measurements are to be
made (current-voltage measuring unit, see Figure 2b). Cur-
rent and voltage measurements can also be individually
made. They must both be switched to the “Energy AC” or
“Energy DC” measurement mode when electrical dimensions
(power, work etc.) are also to be measured.
Fig. 2a: Sensor-Unit Energy (view from above): Voltage and
current inputs, examples of wiring as fixed component in a
circuit, see Fig. 2.
Fig. 2b: Possible wirings for Sensor-Unit Energy
Further important information on the three operating types /
modes:
“u(t), i(t)”: Recording of instantaneous values
“Energy DC”: Moving average for measurement of equal
sizes as well as calculation of real power
and work. The averaging is helpful in the
measurement of small currents or voltages.
This operating mode is also suitable for re-
cording instantaneous values at smaller
scan rates than with “u(t), i(t)”.
“Energy AC”: Effective values (true RMS) of periodic volt-
age and current signals as well as the calcu-
lation of reactive, real and apparent power,
electric work or energy, phase shift in °and
also frequency
The volt and current meters can be separately used In the
operating modes “u(t), i(t)” and “Energy DC”. In the “Energy
AC” operating mode, however, only the voltmeter can be
separately used. The current meter can only be used here
with connected load as is shown by the imprint (measure the
current and voltage of the load as in Fig. 2b).
4 NOTES ON OPERATION
We recommend that you use Cobra4 Sensor-Unit Energy in
combination with a Wireless-Link, as the whole measurement
set-up is then separated from the PC. Parasitic currents to
the mains supply which could affect the measurement results
are hereby avoided. The same benefit is also given when the
Sensor-Unit is used with a laptop computer in battery opera-
tion, i.e. detached from the mains power unit.
Operation of the USB-Link must be via an isolating trans-
former which is not earthed when a computer with connection
to the mains (i.e. a commercial PC or a laptop connected via
a mains power unit) is to be used.
In combination with Cobra4-Wireless-Link, Cobra4-USB-Link,
Cobra4-Junior-Link and Cobra4-Mobile-Link, Cobra4-Sensor-