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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
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www.keithley.com
A GREATER MEASURE OF CONFIDENCE
LOW I/HIGH R PRODUCTS
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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
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A GREATER MEASURE OF CONFIDENCE
Page 3
V
SOURCE
+
–
A/D
R
V
BURDEN
= 200mV at
Full range
Desired Current Reading: I =
V
SOURCE
R
DMM’s Actual Current Reading: I =
V
SOURCE
– V
BURDEN
R
DMM
I
6514 Programmable Electrometer
If:
The desired current reading is: I =
1V
50kΩ
= 20µA
V
SOURCE
= 1V, R = 50kΩ
Actual Reading
(20µA range
on DMM):
I =
1V – 200mV
50kΩ
=
800mV
50kΩ
= 16µA = 20% Burden error
with a DMM
V
BURDEN
= 200mV
6514 Actual Reading:
I =
0.999990V
50kΩ
= 19.9998µA = 0.001% Burden error
with the 6514
V
BURDEN
= 10µV
Refer to Figure 3.
Refer to Figure 2.
Figure 3. Errors Due to Burden Voltage when Measuring with a DMM
The example below compares a DMM’s voltage burden errors with the 6514’s.
DMM Offset Currents
Typically, offset currents in DMMs are tens or hundreds of picoamps, which
severely limits their low current measuring capabilities compared to the Model
6514 with 3fA input bias current.
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AMPS
1
⁄2
-DIGIT 18°–28°C 0°–18°C & 28°–50°C
A, fA=10
5
2
2
2-digit. Rate: Slow (100ms integration time).
–15
A.
CAL
RANGE RESOLUTION ±(%rdg+counts) ±(%rdg+counts)/°C
20 pA 100 aA
200 pA 1 fA
2 nA 10 fA 0.2 + 30 0.1 + 2
20 nA 100 fA 0.2 + 5 0.03 + 1
200 nA 1 pA 0.2 + 5 0.03 + 1
2 µA 10 pA 0.1 + 10 0.005 + 2
20 µA 100 pA 0.1 + 5 0.005 + 1
200 µA 1 nA 0.1 + 5 0.005 + 1
2 mA 10 nA 0.1 + 10 0.008 + 2
20 mA 100 nA 0.1 + 5 0.008 + 1
Notes:
1
When properly zeroed, 51⁄
2
–18
aA =10
INPUT BIAS CURRENT: <3fA at T
INPUT BIAS CURRENT NOISE: <750aA p-p (capped input), 0.1Hz to 10Hz bandwidth, damping on.
Digital filter = 40 readings.
INPUT VOLTAGE BURDEN at T
<20µV on 20pA, 2nA, 20nA, 2µA, 20µA ranges.
<100µV on 200pA, 200nA, 200µA ranges.
<2mV on 2mA range.
<4mV on 20mA range.
TEMPERATURE COEFFICIENT OF INPUT VOLTAGE BURDEN: <10µV/°C on pA, nA, µA ranges.
PREAMP SETTLING TIME (to 10% of final value): 2.5s typical on pA ranges, damping off, 3s typical
on pA ranges damping on, 15ms on nA ranges, 5ms on µA and mA ranges.
NMRR: >95dB on pA, 60dB on nA, µA, and mA ranges at 50Hz or 60Hz ±0.1%. Digital Filter = 40.
VOLTS ACCURACY TEMPERATURE
1
⁄2-DIGIT 18°–28°C 0°–18°C & 28°–50°C
RANGE RESOLUTION ±(%rdg+counts) ±(%rdg+counts)/°C
2 V 10 µV 0.025 + 4 0.003 + 2
20 V 100 µV 0.025 + 3 0.002 + 1
200 V 1 mV 0.06 + 3 0.002 + 1
Note:
1
When properly zeroed, 51⁄2-digit. Rate: Slow (100ms integration time).
NMRR: 60dB on 2V, 20V, >55dB on 200V, at 50Hz or 60Hz ±0.1%.
CMRR: >120dB at DC, 50Hz or 60Hz.
INPUT IMPEDANCE: >200TΩ in parallel with 20pF, < 2pF guarded (10MΩ with zero check on).
SMALL SIGNAL BANDWIDTH AT PREAMP OUTPUT: Typically 100kHz (–3dB).
5
ACCURACY TEMPERATURE
(user adjustable). Temperature coefficient = 0.5fA/°C.
CAL
±1°C (user adjustable):
1
(1 Year)
1 + 30 0.1 + 5
1 + 5 0.1 + 1
1
(1 Year)
COEFFICIENT
COEFFICIENT
OHMS
ACCURACY TEMPERATURE
1
1
⁄2-DIGIT 18°–28°C 0°–18°C & 28°–50°C CURRENT
RANGE RESOLUTION ±(% rdg+counts) ±(% rdg+counts)/°C (nominal)
2kΩ 10 mΩ 0.20+ 10 0.01 + 2 0.9 mA
20 kΩ 100 mΩ 0.15 + 3 0.01 + 1 0.9 mA
200 kΩ 1 Ω 0.25 + 3 0.01 + 1 0.9 mA
2MΩ 10 Ω 0.25 + 4 0.02 + 2 0.9 µA
20 MΩ 100 Ω 0.25 + 3 0.02 + 1 0.9 µA
200 MΩ 1kΩ 0.30 + 3 0.02 + 1 0.9 µA
2GΩ 10 kΩ 1.5 + 4 0.04 + 2 0.9 nA
20 GΩ 100 kΩ 1.5 + 3 0.04 + 1 0.9 nA
200 GΩ 1MΩ 1.5 + 3 0.04 + 1 0.9 nA
1
When properly zeroed, 51⁄2-digit. Rate: Slow (100ms integration time).
MAXIMUM OPEN CIRCUIT VOLTAGE: 250V DC.
PREAMP SETTLING TIME (To 10% of final reading with <100pF input capacitance): 2kΩ through
200kΩ: 2ms; 20MΩ through 200MΩ: 90ms. 2GΩ through 200GΩ: 1s.
A GREATER MEASURE OF CONFIDENCE
5
(1Year)
COEFFICIENT TEST
Model 6514 Specifications
LOW I/HIGH R PRODUCTS
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6514 Programmable Electrometer
COULOMBS
1
⁄2
-DIGIT 18°–28°C 0°–18°C & 28°–50°C
RANGE RESOLUTION ±(%rdg+counts) ±(%rdg+counts)/°C
6
ACCURACY TEMPERATURE
(1 Year)
1,2
COEFFICIENT
20 nC 10 fC 0.4 + 50 0.04 + 10
200 nC 100 fC 0.4 + 50 0.04 + 10
2 µC 1 pC 1 + 50 0.05 + 10
20 µC 10 pC 1 + 50 0.05 + 10
Notes:
1
Charge acquisition time must be <1000s, derate 2% for each additional 10,000s.
2
When properly zeroed, 61⁄2-digit. Rate: Slow (100ms integration time).
INPUT BIAS CURRENT: <4fA at T
. Temperature coefficient = 0.5fA/°C.
CAL
IEEE-488 BUS IMPLEMENTATION
LANGUAGE EMULATION: 6512, 617, 617-HIQ emulation via DDC mode.
TRIGGER TO READING DONE: 150ms typical, with external trigger.
RS-232 IMPLEMENTATION:
Supports: SCPI 1996.0.
Baud Rates: 300, 600, 1200, 2400, 4800, 9600, 19.2k, 38.4k, 57.6k.
Protocols: Xon/Xoff, 7 or 8 bit ASCII, parity-odd/even/none.
Connector: DB-9 TXD/RXD/GND.
Model 6514 Specifications
GENERAL
DISPLAY: 61⁄2-digit vacuum fluorescent.
RANGING: Automatic or manual.
CONVERSION TIME: Selectable 0.01 PLC to 10 PLC.
MAXIMUM INPUT: 250V peak, DC to 60Hz sine wave; 10s per minute maximum on mA ranges.
MAXIMUM COMMON MODE VOLTAGE (DC to 60Hz sine wave): Electrometer, 500V peak.
ISOLATION (Meter COMMON to chassis): Typically 10
INPUT CONNECTOR: Three lug triaxial on rear panel.
2V ANALOG OUTPUT: 2V for full range input. Inverting in Amps and Coulombs mode. Output
impedance 10kΩ.
PREAMP OUTPUT: Provides a guard output for Volts measurements. Can be used as an invert-
ing output or with external feedback in Amps and Coulombs modes.
DIGITAL INTERFACE:
Handler Interface: Start of test, end of test, 3 category bits.
Digital I/O: 1 Trigger input, 4 outputs with 500mA sink capability.
Connector: 9 Pin D subminiature, male pins.
EMC: Conforms to European Union Directive 89/336/EEC.
SAFETY: Conforms to European Union Directive 73/23/EEC (meets EN61010-1/IEC 1010).
GUARD: Switchable voltage and ohm guard available.
TRIGGER LINE: Available, see manual for usage.
READING STORAGE: 2500 readings.
READING RATE:
To internal buffer 1200 readings/second
To IEEE-488 bus 500 readings/second
Notes:
1
0.01 PLC, digital filters off, front panel off, auto zero off.
2
Binary transfer mode.
DIGITAL FILTER: Median and averaging (selectable from 2 to 100 readings).
DAMPING: User selectable on Amps function.
ENVIRONMENT:
Operating: 0°–50°C; relative humidity 70% non-condensing, up to 35°C.
Storage: –25° to +65°C.
WARM-UP: 1 hour to rated accuracy (see manual for recommended procedure).
POWER: 90–125V or 210–250V, 50–60Hz, 60VA.
PHYSICAL:
Case Dimensions: 90mm high × 214mm wide × 369mm deep (3
Working Dimensions: From front of case to rear including power cord and IEEE-488 con-
nector: 15.5 inches.
10
Ω in parallel with 500pF.
1
1, 2
1
⁄2 in. × 83⁄8 in. × 149⁄16 in.).
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LOW I/HIGH R PRODUCTS
www.keithley.com
A GREATER MEASURE OF CONFIDENCE
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