Hameg HM8115-2 Manual page 34

C o n c e p t o f t h e H M 8 1 1 5 - 2
Concept of the HM8115-2
The HM8115-2 uses true rms converters for measuring volta-
ge and current. The instantaneous power is measured using
an analog multiplier. The active power is derived by integra-
ting the instantaneous power for a period T. All other values
are calculated.
The apparent power:
S = V x I
rms
The reactive power
2 2
Q = S – P
The power factor PF = P/S. This will always yield the correct
power factor because the cosj is only defi ned for purely sinus-
oidal signals. However, in SMPS, motor controls etc. nonsinu-
soidal 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.
Introduction to the Operation of the HM8115-2
Please read the instruction manual carefully.
At fi rst time operation please observe the following recom-
mendations:
– The mains voltage selector
voltage, and the correct fuse has been installed inside the
mains connector
– 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 fl oating around inside the instru-
ment.
Self Test
After turn-on with power switch
FUNCTION will show the nuber of the fi rmware implemented,
e.g. „2.01".

The LED display FUNCTION shows the baud rate of the se-
rial interface, e.g. „9600".
32
Subject to change without notice
.
rms
has been set to the correct
Œ 
the 3 rd display for the
The instrument will automatically go into the active power
measurement mode, the LED located near "FUNCTION
and labelled "WATT" will light up. The AUTO range function will
select the optimum ranges for voltage and current.
Operating controls and Displays
Œ
Power
This is the mains switch labelled "I" = On and "0" = Off.
After turn-on the LED display for "FUNCTION
a moment the number of the version of fi rmware 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. Au-
toranging will be active and select the optimum ranges for
voltage and current.

VOLT display
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 appro-
priate range the righthand VOLT pushbutton Å must be used
or the autorange function selected.
Ž
AMPERE display
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
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
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.
"

" will show for
“
pushbutton must