Keithley 6514 Datasheet
6514 Programmable Electrometer
The Model 6514 Electrometer combines flexible interfacing capabilities with current sensitivity, charge
measurement capabilities, resolution, and speed that
are equal or superior to our earlier electrometers. The
Model 6514’s built-in IEEE-488, RS-232, and digital I/O
interfaces make it simple to configure fully automated,
high speed systems for low-level testing.
1
The 6
⁄2-digit Model 6514 is designed for applications
that demand fast, yet precise measurements of low
currents, voltages from high resistance sources,
charges, or high resistances.
The Model 6514’s exceptional measurement performance comes at an affordable price. While its cost is
comparable with that of many high-end DMMs, the
Model 6514 offers far greater current sensitivity and
significantly lower voltage burden (as low as 20µV)
• <1fA noise
• >200TΩ input impedance on
voltage measurements
• Charge measurements from
10fC to 20µC
• High speed—up to 1200
readings/second
• Interfaces readily with switches,
computers, and component
handlers
• Cancels voltage and current
offsets easily
Ordering Information
6514 Programmable
Electrometer
Extended warranty, service, and
calibration contracts are available.
Accessories Supplied
237-ALG-2 Low Noise Triax
Cable, 3-Slot Triax to Alligator
Clips, 2m (6.6 ft)
R&D on a Budget
The Model 6514 offers the flexibility and sensitivity needed for a wide array of experiments, providing better data far faster than older electrometer designs. Applications include measuring currents from light
detectors and other sensors, beam experiments, and measuring resistances using a current source. In
addition to use by researchers in areas such as physics, optics, and materials science, the Model 6514’s
affordable price makes it an attractive alternative to high-end DMMs for low-current measurement applications, such as testing resistance and leakage current in switches, relays, and other components. For more
information on how the Model 6514 does this, refer to the section titled “Low Voltage Burden.”
The Model 6514 builds on the features and capabilities of the Keithley electrometers that preceded it. For
example, like those instruments, a built-in constant current source simplifies measuring resistance.
Two analog outputs—a 2V output and a preamp output—are available for recording data with strip-chart
recorders.
ACCESSORIES AVAILABLE
CABLES
237-ALG-2 Low Noise Triax Cable, 3-Slot Triax to Alligator
7007-1 Shielded IEEE-488 Cable, 1m (3.2 ft)
7007-2 Shielded IEEE-488 Cable, 2m (6.5 ft)
7009-5 RS-232 Cable
7078-TRX-3 Low Noise Triax Cable, 3-Slot Triax Connectors,
7078-TRX-10 Low Noise Triax Cable, 3-Slot Triax Connectors,
7078-TRX-20 Low Noise Triax Cable, 3-Slot Triax Connectors,
8501-1 Trigger-Link Cable, 1m (3.3 ft)
8501-2 Trigger-Link Cable, 2m (6. ft)
SOFTWARE
TestPoint Software Package
RACK MOUNT KITS
4288-1 Single Fixed Rack Mounting Kit
4288-2 Dual Fixed Rack Mounting Kit
Clips
0.9m (3 ft)
3m (10 ft)
6m (20 ft)
than other instruments can provide.
ADAPTERS
7078-TRX-BNC 3-Lug Triax to BNC Adapter
237-TRX-NG Triax Male-Female Adapter with Guard
Disconnected
237-TRX-T 3-Slot Male Triax to Dual 3-Lug Female Triax Tee
Adapter
237-TRX-TBC 3-Lug Female Triax Bulkhead Connector
(1.1kV rated)
7078-TRX-TBC 3-Lug Female Triax Bulkhead Connector
with Cap
OTHER
KPCI-488 IEEE-488 Interface/Controller for the PCI Bus
KPC-488.2AT IEEE-4888 Interface Card for IBM PC/AT (full
slot)
KPC-TM Trigger Master Interface
1050 Padded Carrying Case
5156 Calibration Standard Set
6514-EW 1 Year Warranty Extension
Fast, precise current, charge, voltage, and resistance measurements
1.888.KEITHLEY (U.S. only)
www.keithley.com
A GREATER MEASURE OF CONFIDENCE
LOW I/HIGH R PRODUCTS
I
D
6514 Electrometer
R
L
IL = 0
Photodiode
(no incident
light)
–
+
V
BURDEN
A/D
CAL V
OFFSET
Total offset
voltage = 0
Leakage
Resistance
R
L
I
L
(error current
due to
V
BURDEN
)
Photodiode
(no incident
light)
–
+
V
BURDEN
A/D
I
D
Electrometer
6514 Programmable Electrometer
Economical Component Testing
Once, electrometers were simply considered too slow to keep up with the high throughput that production test applications demand. The Model 6514 is designed for fast, sensitive measurements, providing
speeds up to 1200 readings per second with fast integration or 17 measurements per second with 60Hz
line-cycle integration. It offers 10fA resolution on 2nA signals, settling to within 10% of the final value in
just 15ms. A normal-mode rejection ratio (NMRR) of 60dB allows making accurate low current measurements, even in the presence of line frequency induced currents, which is a common concern in production floor environments. The instrument’s sensitivity makes it easy to determine the leakage resistance on
capacitances up to 10nF or even on higher capacitances when a series resistor is used.
While the Model 6514 can be easily operated manually using the front panel controls, it can also be externally controlled for automated test applications. Built-in IEEE-488 and RS-232 interfaces make it possible
to program all instrument functions over the bus through a computer controller. The instrument’s interfaces also simplify integrating external hardware, such as sources, switching systems, or other instruments, into the test system. A digital I/O interface can be used to link the Model 6514 to many popular
component handlers for tight systems integration in binning, sorting, and similar applications.
These features make the Model 6514 a powerful, low-cost tool for systems designed to test optical devices
and leakage resistance on low-value capacitors, switches, and other devices, particularly when the test system already includes a voltage source or when the source current/measure voltage technique is used to
determine resistance.
Low Voltage Burden
The Model 6514’s feedback ammeter design minimizes voltage offsets in the input circuitry, which can
affect current measurement accuracy. The instrument also allows active cancellation of its input voltage
and current offsets, either manually via the front panel controls or over the bus with IEEE-488 commands.
Dark Current Measurements
When measuring dark currents (Figure 1) from a device such as a photodiode, the ammeter reads the
sum of two different currents. The first current is the dark current (I
light falling upon the device (in other words, the signal of interest); the second one is the leakage current
(I
) generated by the voltage burden (V
L
ammeter, the primary “voltage burden” is the amplifier offset voltage. This leakage current represents an
BURDEN
error current. Without the use of cancellation techniques, I
Fast, precise current, charge, voltage, and resistance measurements
Figure 1. Dark Current Measurement with
Burden Voltage Uncorrected
Model 6514’s CAL V
so the measured current is only the true dark current (I
currents can also be cancelled. Earlier electrometers used an internal numerical correction technique in
which the voltage burden was still present, so the measured dark current included the error term
I
L
= V
BURDEN/RL
.
is adjusted to cancel V
OFFSET
Voltage Burden and Measurement Error
Electrometers provide current measurement with lower terminal voltage than is possible when making DMM
measurements. As shown in Figure 3, DMMs measure current using a shunt resistance that develops a voltage
(typically 200mV full-range) in the input circuit. This creates a terminal voltage (V
by lowering the measured current. Electrometers reduce this terminal voltage by using the feedback ammeter
configuration illustrated in Figure 1. The Model 6514 lowers this terminal voltage still further—to the level of
the voltage noise—by canceling out the small offset voltage that remains, as shown in Figure 2. Any error signals that remain are negligible in comparison to those that can occur when measuring current with a DMM.
Figure 2. Dark Current Measurement with
Burden Voltage Corrected
) appearing at the terminals of the ammeter. In a feedback
L
to within the voltage noise level of a few microvolts,
BURDEN
) of the photodiode. In a similar manner, offset
D
) generated by the detector with no
D
= V
. Figure 2 illustrates how the
BURDEN/RL
) of about 200mV, there-
BURDEN
LOW I/HIGH R PRODUCTS
1.888.KEITHLEY (U.S. only)
www.keithley.com
A GREATER MEASURE OF CONFIDENCE
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