Dual Measurement Mode
In Dual Measurement Mode a completely independent but complementary measurement can be
made and displayed on the secondary display. The two independent measurements are actually
made alternately, not simultaneously, and the display update rate for each measurement is
consequently reduced. Note that this is not the same as when, in dual display mode, both a
measurement and a modified version of that measurement are displayed, e.g. ac Volts and the
dB equivalent; in this case only a single measurement is being made and the measurement rate
is unchanged; further information is given later in this section.
Dual Measurement Combinations
All practical combinations of functions are allowed in Dual Measurement Mode; those of no
practical use (e.g. dc Volts and Frequency) are not selectable. The full list is as follows:
Main Display Secondary Display
Vdc Vac, Idc, Iac
Vac Vdc, Idc, Iac, Hz
Idc Vdc, Vac, Iac
Iac Vdc, Vac, Idc, Hz
Hz Vac, Iac
Capacitance, Ω, and Continuity/Diode check cannot meaningfully be combined with other
measurements and are therefore always excluded from the secondary display. Vac+Vdc and
Iac+Idc are also excluded because they already involve dual measurements; when they are being
used no secondary display can be set.
The same measurement can be displayed in both displays, if required, at the single measurement
update rate; in this mode the displays both use the range set for the main display.
The secondary display is selected by pressing Select 2nd followed by the function; pressing an
illegal function will cause a warning beep and the key entry will be ignored. Pressing Select 2nd
twice will return the meter to single measurement mode with the range shown in the secondary
display; pressing Select 2nd followed by Cancel turns the secondary display off. Selecting any
main display function will also return the meter to single measurement mode.
The secondary measurement, with the exception of the 10A current ranges, always autoranges.
The 10A current ranges are set by first selecting the function (Select 2nd followed by Iac or Idc)
then pressing Select 2nd followed by Range Up; return to the mA autoranges is by pressing
Select 2nd followed by Range Down. However, if both main and secondary displays are making
current measurements, the range of the secondary measurement is always that of the main
display.
If Vdc and Vac are the two measurement functions, autoranging of the secondary display is
restricted such that the dc measurement range is not lower than the ac range; this ensures that
the dc measurement is not affected by a high ac signal, see the table in the Specification (page
3). For example, if the main display is set to 10Vdc the secondary display can autorange between
the 100mV, 1000mV and 10Vac ranges. In this example, low levels of ripple could be measured
(on the 100mV range) on a 10Vdc supply rail, but an ac input >12V will cause the secondary
display to flash 12000 (overload) warning the user to select a higher main display dc range such
that the secondary ac measurement is in range. Similarly, if the main display is set to 100Vac
then the secondary display will not autorange below 100Vdc, even for small dc inputs.
When frequency is selected for the secondary display the measurement is made using the ac
range set in the main display. This presents no problems if the main display is in autorange but if
a higher range has been set manually, such that the reading is less than 10% of the range
maximum, the signal level may not be adequate for frequency measurement.
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