Keithley 6487 Reference Manual

3-4 Measurements and Sourcing Voltage Model 6487 Reference Manual
SCPI programming
SYSTem:AZERo[:STATe] <b>
Sending this command over the bus does not update the display while in remote. To verify
the AZERo state, send the query. The displayed autozero state will be updated when the
instrument is placed back in local.
Programming example
The following examples enable or disable the autozero feature:
SYST:AZER ON ' Enable autozero.
SYST:AZER OFF ' Disable autozero.
SYST:AZER? ' Query autozero. 1=on, 0=off
Zero check and zero correct
Zero check
When zero check is enabled (on), the input amplifier is reconfigured to shunt the input sig-
nal to low with the input impedance (Figure 3-1).
klqb The ZCHK key toggles zero check on and off. If zero check is enabled
(“ZEROCHK” message displayed), press ZCHK to disable it.
From the front panel, enable/disable zero check by pressing the ZCHK key (ZEROCHK
message displayed). Refer to Table 3-4 for bus commands.
klqb Leave zero check enabled when connecting or disconnecting input signals.
Figure 3-1
Equivalent input impedance with zero check enabled
Table 3-3
SCPI commands — autozero
Command Description Default
SYSTem
:AZERo
[:STATe] <b>
SYSTem Subsystem:
Enable or disable autozero.
ON
C
IN
Input R
IN
510Ω ||200nF .......... 2mA, 20mA
50kΩ || 2nF.............. 20mA, 200μA
3.5MΩ || 120pF ....... 200nA, 2μA
11MΩ || 100pF ........ 2nA, 20nA

Keithley 6487 Specifications

General

Type	Picoammeter/Voltage Source
Current Measurement Range	20 fA to 20 mA
Interfaces	GPIB, RS-232
Voltage Burden	< 200 µV
Input Impedance	>10^14 Ω
Power	100 V / 120 V / 220 V / 240 V
Basic Current Measurement Accuracy	0.4%