HP 34970A manual Sdd’s signal-conditioning

Chapter 3 System Overview

Measurement Input

N N	s		Ox
””“ x			Sdd’s signal-conditioning
section – zx z3 x“ xx
zz x x “z 3 ” x”
z”“ xx ” ” x x
“z x ” ””5 Y ”
xz 3 x z”“		z”” xz	”
“z ” /”		idj 5 i”” ” x” ” y
x z z””xz” x x
z ” “ xz ” ”x				3
z3 ”” ” x3 z””
z ”	x”

xSdd’s analog-to-digital converter (OSR).

You can allow the instrument to automatically select the measurement

range using	or you can select a fixed measurement range
using	. Autoranging is convenient because the instrument

automatically decides which range to use for each measurement based on the input signal. For fastest scanning operation, use manual ranging for each measurement (some additional time is required for autoranging since the instrument has to make a range selection).

sOv usvuIThe OSR takes a prescaled dc voltage from the signal-conditioning circuitry and converts it to digital data for output and display on the front panel. The OSR governs some of the most basic measurement characteristics. These include measurement resolution, reading speed, and the ability to reject spurious noise. There are several analog-to-digital conversion techniques but they can be

divided into two types:and. The integrating techniques measure the average input value over a defined time interval, thus rejecting many noise sources. The non-integrating techniques sample the instantaneous value of the input, plus noise, during a very short interval. The internal Sdd uses an integrating OSR technique.

You can select the resolution and reading speed from 6 digits (22 bits) at 3 readings per second to 4 digits (16 bits) at up to 600 readings per second.

The W menu from the HP 34970A front panel allows you to control the integration period for precise rejection of noise signals.

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