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C o n c e p t o f t h e H M 8 1 1 5 - 2
4 Concept of the HM8115-2
The HM8115-2 uses true rms converters for measuring voltage
and current. The instantaneous power is measured using an
analog multiplier. The active power is derived by integrating
the instantaneous power for a period T. All other values are
calculated.
The apparent power:
S = V
x I
.
rms
rms
The reactive power
Q =
S
2
– P
2
The power factor PF = P/S. This will always yield the correct po-
wer factor because the cosϕ is only defined for purely sinusoidal
signals. However, in SMPS, motor controls etc. nonsinusoidal
signals are prevalent.
The instantaneous power can be taken off the rear panel ter-
minal and shown on a scope. The HM8115-2 can be remotely
controlled via the serial interface, also all values can be read
via the interface. Measuring circuit, monitor output and serial
interface are isolated from each other.
5 Introduction to the Operation
Please read the instruction manual carefully.
At first time operation please observe the following recom-
mendations:
–
The mains voltage selector
voltage, and the correct fuse has been installed inside the
mains connector
17
–
Proper connection to an outlet with safety ground contact
or an isolation transfomer has been made.
–
There are no visible damages to the instrument
–
There are no loose parts floating around inside the instru-
ment.
Self Test
After turn-on with power switch
FUNCTION will show the nuber of the firmware implemented,
e.g. „2.01".
The LED display
FUNCTION shows the baud rate of the serial
4
interface, e.g. „9600".
32
Subject to change without notice
has been set to the correct
16
the 3
rd
display
for the
1
4
The instrument will automatically go into the active power
measurement mode, the LED located near FUNCTION
labelled WATT will light up. The AUTO range function will select
the optimum ranges for voltage and current.
6 Operating controls and Displays
Power
1
This is the mains switch labelled "I" = On and "0" = Off.
After turn-on the LED display for FUNCTION
moment the number of the version of firmware installed , e.g.
"2.01", then the baud rate of the serial interface, e.g. "9600",
then it will go into the active power measurement mode. The
LED near FUNCTION
labelled WATT will light up. Autoran-
11
ging will be active and select the optimum ranges for voltage
and current.
VOLT display
2
This display will indicate the voltage on the output . Due to the
drop across the shunt this voltage will be slightly reduced with
respect to the input voltage. In case of overrange the display will
show blinking horizontal bars. In order to go to the appropriate
range the righthand VOLT pushbutton
autorange function selected.
AMPERE display
3
This displays shows the current. In case of overrange the dis-
play will show blinking horizontal bars. In order to go to the
appropriate range the righthand AMPERE
be activated or the autorange function selected.
FUNCTION display
4
The FUNCTION display will indicate the measurement result
of the selected function.
These function can be chosen:
–
Active power in watts
–
Reactive power in voltamperes reactive
–
Apparent power in voltamperes
–
Power factor PF
The function desired can be selected using the FUNCTION
pushbuttons, the selected function will be indicated by the
10
proper LED.
If either the voltage or the current range or both too low or high
in order to achieve a meaningful result the FUNCTION display
will show 3 to 4 horizontal bars irrespective of the function
selected.
In PF mode such bars indicate that no meaningful power factor
can be calculated. There are several possible reasons:
1. No current or pure DC current.
2. No voltage or pure DC voltage.
3. Either the voltage or the current or both are too low.
4. Manually selected voltage or/and current ranges are too
low or too high.
and
11
will show for a
4
must be used or the
6
pushbutton must
8
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