Manual

Gossen Metrawatt GmbH 37
Voltage Comparator for Displaying Dangerous Voltage
The input signal or measuring signal is checked by a voltage com-
parator for dangerous spikes, because these do not appear at the
display when the low-pass filter is used.
At voltages of greater than 15 V AC or 25 V DC, a danger symbol
appears at the display:
Note
The “Setup for present measurement” submenu cannot
be accessed for the above described measurements
because no further settings are available.
8.6.2 Duty Cycle Measurement – Duty AC
(METRAHIT IM XTRA BT and METRAHIT IM E-DRIVE BT only)
The pulse-period ratio can be ascertained for square-wave sig-
nals with the duty cycle measurement.
➭ Set the rotary switch to V~.
➭ Repeatedly press the Func softkey until Duty AC appears at the
display.
➭ Connect the measurement cables as you would for a voltage
measurement.
Make sure that a current measuring range (“A”) has not been acti-
vated when the multimeter is connected for frequency or duty
cycle measurement!
The ratio of pulse duration to pulse period is measured with peri-
odic square-wave signals and is displayed as a percentage.
Note
The applied frequency must remain constant during duty
cycle measurement.
8.6.3 RPM Measurement – RPM AC
(METRAHIT IM XTRA BT and METRAHIT IM E-DRIVE BT only)
Revolutions per minute at 2 and 4-stroke internal combustion
engines (also known as rotational frequency) are measured by
acquiring pulses. The number of measurable pulses per revolution
varies depending upon engine type (2 or 4 stroke).
As a prerequisite
for this measurement, the number of measurable pulses per revolution
must first be set in the RPM settings menu (RPM
 0FF) (see
below).
➭ Set the rotary switch to V~.
➭ Repeatedly press the Func softkey until RPM AC appears at the
display.
➭ Select the desired engine type, i.e. 2-T or 4-T with the

scroll keys.
➭ Connect the measurement cables as you would for a voltage
measurement. In the case of internal combustion engines, ig-
nition pulses can be acquired alternatively with a current sen-
sor (see wiring diagram).
➭ The measured value then appears in RPM, for example
“244.3 r”.
Measured RPM value Revolutions Per Minute
RPM parameter Pulses per revolution
Pulses per Revolution Settings Menu
2-T RPM measurement at 2-stroke engines:
1 pulse per revolution) or
4-T RPM measurement at 4-stroke engines:
1 pulse per 2 revolutions)
Voltage Comparator for Displaying Dangerous Voltage
The input signal or measuring signal is checked by a voltage com-
parator for dangerous spikes, because these do not appear at the
display when the low-pass filter is used.
At voltages of greater than 15 V AC or 25 V DC, a danger symbol
appears at the display:
Duty cycle (%) =
Pulse duration (t
E
)
Pulse period (t
P
)
 100
RPM
revolutions
min
-------------------------------
pulses
revolution
--------------------------- -



x
60s
s
--------
=