QuadTech 1865, Инструкция по эксплуатации, Страница: 40 / 87

Page 40 of 87 Operation
2.6.2.7 Range
Range
I/O Utilities
1 mA
100 uA
10 uA
1 uA
100 nA
10 nA
1 nA
Setup
Auto
Figure 2-13: Range Selection
Through a lower level menu (by pressing [ENTER]) allows for selection of
Auto or one
of seven different measurement ranges ( 1mA through 1nA ), which is the maximum
current for the selected range. In auto mode the 1865 instrument will automatically
select the optimum range depending on the programmed test voltage and current drawn
by the test device. Any choice other than Auto (1mA through 1nA range) is at the user's
discretion. Determination of the range is governed by the maximum current available to
the DUT for that measurement range and is listed in Table 2-1.
To eliminate operator
errors in range setting and ensure specified instrument accuracy the 1865 unit
should generally be left in AUTO.
There may be an exception to this when repetitive
measurements are to be made on a known range and there is a desire to reduce test time
by eliminating range switching. When auto ranging is selected the 1865 instrument will
always begin the measurement phase on the highest current range, 1mA and progress
down depending on the current to the device under test. If the current reaches 10% or
less of the maximum for a given range the next lowest range will be switched in.
If a range has been selected and the current exceeds 115% of the maximum for that range
the unit will indicate OVER RANGE on the display. One needs to keep in mind that an
over range does not necessarily mean the incorrect range has been selected, the device
under test could also be defective. Over range should not be confused with an
OVERLOAD display. Overload occurs anytime current to a device attempts to exceed
2mA, this would generally mean a shorted or very low resistance device.