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6517B-900-01 Rev. A / Jun 2008 Return to Section Topics 3-3

Model 6517B Electrometer User’s Manual Section 3: Basic Measurements

Figure 3-1

Voltage measurements

Guarding

Guarding should be used for high impedance (>10

Ω) voltage measurements and for voltage

measurements when using long input cables. In a high impedance circuit, guarding greatly

reduces leakage currents. When using long input cables, guarding cancels the effects of cable

capacitance that can significantly slow down the measurement response time.

When GUARD is enabled, the INPUT triax connector

is reconfigured to apply the guard potential

to the inner shell of the INPUT triax connector. With this configuration, the COMMON banana jack

is used for input low. Figure 3-1 shows both the guarded and unguarded configurations for the

INPUT connector.

Perform the following steps to enable or disable guard:

1. Press CONFIG an

d then V to display the volts configuration menu.

2. Use the and keys to place the cursor (blinking menu item) on GUARD and press

ENTER.

3. Place the cursor on the desired selection (OFF to disable or ON to enable) and press

ENTER.

4. Use the EXIT key to back out of the menu.

Red (HI)

Black (LO)

6517B

Shield (Optional)

Measured

Voltage

Red (HI)

6517B

Safety

Shield

Safety

Earth

Ground

Measured

Voltage

Triax

Cable

A. Unguarded (GUARD off)

Triax

Cable

Guard

Black

Green

B. Guarded (GUARD on)

OPTION SLOT

250VDC MAX

MADE IN

U.S.A

LINE RATING

50-60 Hz

100 VA MAX.

LINE

WARNING: NO INTERNAL OPERATOR SERVICABLE PARTS, SERVICE BY QUALIFIED PERSONNEL ONLY.

CAUTION: FOR CONTINUED PROTECTION AGAINST FIRE HAZARD, REPLACE FUSE WITH SAME TYPE AND RATING.

1250Vpk

PREAMP

OUT

1000VDC

MAX

FUSE

630mAT

315mAT

100V

120V

220V

240V

COMMON 2V OUT

LO HI

V SOURCE

TRIGGER LINK RS-232

DIGITAL I/O

HUMIDITY

TEMP

TYPE K

INTERLOCK

IEEE-488

2VDC MAX