Operator`s manual

Signametrics 34
r low currents from such circuits as Current
utput DACs of such devices as heart pace makers, or low semiconductor leakages can be measured with practically
guarding
arning! Applying voltages greater than 35 V to the I+, I- terminals can cause personal injury and/or
4.2.1 Extended DC Current Measurements (SM2064)
In addition to the 2.4mA, 24mA, 240mA and 2.4A, the SM2064 has also four DC current ranges; 240nA, 2.4uA,
24uA and 240uA ranges. The lower three ranges are implemented with a “Virtual Zero Shunt” technology,
commonly associated with specialized Micro Amp meters. It has an ultra low noise low leakage that renders it
useful for measuring down to few Pico-amperes. This means that supe
o
no voltage drop.
In order to measure down to Pico Amperes it may be necessary to guard the terminals as described in the
section of this manual (4.3.8
Guarding High Value Resistance Measurements (SM2064)) .
W
damage to your DMM and computer! Think before applying any inputs to these terminals!
Figure 4-2. AC and DC Current measurement connection.
4.2.2 Improving DC Current Measurements
When making sensitive DC current measurements disconnect all terminals not associated with the measurement.
User the Relative function while in the desired DC current range to zero out any residual error. Using the S-Cal
(DMMCalibrate ()) prior to activating Relative will improve accuracy further. Although the SM2060 family is
designed to withstand up-to 2.4A indefinitely, be aware that excessive heat may be generated when measuring
high ts. In
be limited to
ts
his
rrents with a
er AC or DC currents. If allowed to rise this heat may adversely effect subsequent measuremen
consideration with this effect, it is recommended that whenever practical, higher current measurements
short time intervals. The lower two ranges of DC current may be effected by relay contamination. If the
measurements seem unstable or high, while in IDC measurement, apply between 20mA and 50mA DC to the
current terminals and clean the K2 relay using the DMMCleanRelay(0, 2, 200). Repeat this until the measuremen
are stable.
4.2.3 DC Current Measurements at a specific voltage
The leakage measurement function can be used to measure low-level currents at a specific voltage. T
function uses the top and bottom terminals of the SM2064. It measures low level DC cu
specified DC voltage applied to the DUT.