Tektronix KEITHLEY 2600B Series User Manual

Section 5: Theory of operation Series 2600B System SourceMeter® instrument Reference Manual
5-24 2600BS-901-01 Rev. F/August 2021
Analog-to-digital converter
The 2600B SMUs have integrating analog-to-digital converter (ADCs). The integrating ADCs use a
ratiometric analog-to-digital conversion technique. Depending on the configuration of the integrating
ADCs, periodic fresh reference measurements are required to minimize drift. The measurement
aperture is used to determine the time interval between these measurement updates. For additional
information, see Autozero (on page 2-8). To optimize operation of these ADCs, the instrument caches
the reference and zero values for the ten most recent power-line cycles. For additional information,
see NPLC caching (on page 2-9).
Measurement settling time considerations
Several outside factors can influence measurement settling times. Effects such as dielectric
absorption, cable leakages, and noise can all extend the times required to make stable
measurements. Be sure to use appropriate shielding, guarding, and aperture selections when making
low-current measurements.
Each current measurement range has a combination of a range resistor and a compensating
capacitor that must settle to allow a stable measurement. By default (when power is turned on or after
a smuX.reset() command), delays are enforced to account for approximately 6 or 6 time
constants of a given range (to reach 0.1 percent of the final value, assuming 2.3 per decade). The
table below lists the current ranges and associated default delays. In addition, a 1 Hz analog filter is
used by default on the 1 nA and 100 pA ranges.
Current measure settling time
1, 2
Time required to reach 0.1% of final value after source level command is
processed on a fixed range.
Values below for V
OUT
= 2 V unless otherwise noted.
Current range
Settling time
1.5 A to 1 A
<120 μs (typical) (R
LOAD
>6 Ω)
100 mA to 10 mA
<80 μs (typical)
1 mA
<100 μs (typical)
100 μA
<150 μs (typical)
10 μA
<500 μs (typical)
1 μA
<2.5 ms (typical)
100 nA
<15 ms (typical)
10 nA
<90 ms (typical)
1 nA
1
<360 ms (typical)
100 pA
3
<360 ms (typical)
1. Delay factor set to 1. Compliance equals 100 mA.
2. Time for measurement to settle after a V
STEP
.
3. With default analog filter setting <450 ms.

Tektronix KEITHLEY 2600B Series Specifications

General

Brand	Tektronix
Model	KEITHLEY 2600B Series
Category	Measuring Instruments
Language	English