More On Autoranging; Reducing Settling Waits; Background - HP E1313A Manual

More On Autoranging

Reducing Settling Waits

Background

144 Understanding the HP E1313/E1413
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There are rare circumstances where your input signal can be difficult for the
HP E1313/E1413 to autorange correctly. The module completes the range
selection based on your input signal about 6 µsec before the actual
measurement is made on that channel. If, during that period, your signal
becomes greater than the selected range can handle, the module will return
an overflow reading (± INFinity
You can cure this problem by selecting a high enough manual range for that
particular channel while leaving others in autorange (see the
[SENSe:]FUNCtion:... commands in Chapter 5). You can also set the
lowest allowable range that autorange can select for each channel by
executing DIAGnostic:FLOor[:CONFigure] <
Some sequences of input signals, as determined by their order of appearance
in a scan list, can be a challenge to measure accurately. This section is
intended to help you determine if your system presents any of these
problems and how best to eliminate them or reduce their effect.
While the HP E1313/E1413 can autorange, measure, and convert a reading
to engineering units as fast as once every 10 µs, measuring a high-level
signal followed by a very low-level signal may require some extra settling
time. As seen from the point of view of the HP E1313/E1413's
Analog-to-Digital converter and its Range Amplifier, this situation is the
most difficult to measure.
For example, lets look at two consecutive channels; the first measures a
power supply at 15.5 volts, the next measures a thermocouple temperature.
First the input to the Range Amplifier is at 15.5 volts (near its maximum)
with any minute capacitances charged accordingly, then it immediately is
switched to a thermocouple channel and down-ranged to its .0625 volt
range. On this range, the resolution is now 1.91 µvolt per Least Significant
Bit (LSB). Because of this sensitivity, the time to discharge these minute
capacitances may have to be considered.
).
range >,(@< ch_list >) .
Chapter 4