Scanning
Each channel of scan configuration can be associated with a unique digital multimeter (DMM)
configuration (which includes a range setting). When a scan completes, the DMM remains in the
configuration associated with the last completed measurement step. For remote programming, the
channel list parameter is used to configure channels for a scan.
See dmm.configure.set() (on page 11-166), dmm.setconfig() (on page 11-227), scan.create() (on
page 11-315), and scan.add() (on page 11-309) commands, and the Scanning and triggering (on
page 5-23) section for more details, including front panel operation.
Optimizing measurement speed
Rate
The integration time (measurement speed) of the A/D converter controls how long the input signal is
measured (also known as aperture). The integration time affects the amount of reading noise, as well
as the ultimate reading rate of the instrument.
The integration time is specified in parameters based on a number of power line cycles (NPLC),
where 1 PLC for 60 Hz is an aperture of 16.67 ms (1/60) and 1 PLC for 50 Hz is 20 ms (1/50).
In general, the fastest integration time is 0.1 PLC using the front panel RATE key, or 0.0005 PLC
from the remote interface or through the DMM > CONFIG NPLC menu. This results in increased
reading noise and fewer usable digits.
The slowest integration time is 5 PLC using the front panel RATE key, or 15 PLC from the remote
interface or through the DMM > CONFIG NPLC menu. This provides the best common-mode and
normal-mode rejection.
In-between settings are a compromise between speed and noise.
The Series 3700A has a parabola-like shape for its speed versus noise characteristics. The Series
3700A is optimized for the 1 PLC to 5 PLC reading rate. At these rates (lowest noise region in graph),
the Series 3700A will make corrections for its own internal drift and will still be fast enough to settle a
step response of less than 100 ms.
Figure 66: Speed compared to noise characteristics
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