www.keithley.com Model 6485 Picoammeter Model 6487 Picoammeter/Voltage Source User’s Manual 6487-900-01 Rev.
Model 6485 Picoammeter Model 6487 Picoammeter/Voltage Source User’s Manual © 2002-2011, Keithley Instruments, Inc. Cleveland, Ohio, U.S.A. All rights reserved. Any unauthorized reproduction, photocopy, or use the information herein, in whole or in part, without the prior written approval of Keithley Instruments, Inc. is strictly prohibited. All Keithley Instruments product names are trademarks or registered trademarks of Keithley Instruments, Inc.
Safety Precautions The following safety precautions should be observed before using this product and any associated instrumentation. Although some instruments and accessories would normally be used with non-hazardous voltages, there are situations where hazardous conditions may be present. This product is intended for use by qualified personnel who recognize shock hazards and are familiar with the safety precautions required to avoid possible injury.
For maximum safety, do not touch the product, test cables, or any other instruments while power is applied to the circuit under test. ALWAYS remove power from the entire test system and discharge any capacitors before: connecting or disconnecting cables or jumpers, installing or removing switching cards, or making internal changes, such as installing or removing jumpers. Do not touch any object that could provide a current path to the common side of the circuit under test or power line (earth) ground.
Table of Contents 1 Getting Started Introduction ................................................................................ 1-2 Overview of this manual ............................................................ 1-2 General information ................................................................... 1-2 Warranty information ......................................................... 1-2 Contact information ............................................................ 1-3 Safety symbols and terms ...
Ohms measurement connections ......................................... 2-4 Noise and safety shields ...................................................... 2-5 Using a test fixture ...................................................................... 2-6 General purpose test fixture ................................................ 2-6 Model 8009 resistivity test fixture ...................................... 2-6 Interlock ......................................................................................
Damping ..................................................................................... Filters ......................................................................................... Median filter ....................................................................... Digital filter ......................................................................... Filter control ....................................................................... 5 Relative, mX+b, m/X+b (reciprocal), and log Relative .
B General Measurement Considerations Measurement considerations ..................................................... Ground loops ...................................................................... Triboelectric effects ............................................................ Piezoelectric and stored charge effects .............................. Electrochemical effects ...................................................... Humidity ...................................................................
Model 6485 and 6487 User’s Manual Getting Started 1-1 1 Getting Started • • • • • • • • • • Introduction — Description of the Models 6485 and 6487 Picoammeters. Overview of this manual — Provides content of this manual. General information — Covers general information that includes warranty infor- mation, contact information, safety symbols and terms, unpacking and inspection, and available options and accessories. Features — Summarizes the features of Models 6485 and 6487.
1-2 Getting Started Model 6485 and 6487 User’s Manual Introduction The Models 6485 and 6487 are high-resolution bus-programmable (RS-232 and IEEE-488) picoammeters. The Models 6485 and 6487 have the following current measurement ranges: eight ranges (from 20mA down to the 2nA range). The Model 6487 also includes a ±500V DC voltage source and an ohms function that includes an alternating voltage mode to improve accuracy and repeatability of very high resistance measurements.
Model 6485 and 6487 User’s Manual Getting Started 1-3 Safety symbols and terms The following symbols and terms may be found on the instrument or used in this manual: If or is present, connect it to safety earth ground using the wire recommended in the user documentation. The ! symbol on an instrument indicates that the user should refer to the operating instructions located in the manual.
1-4 Getting Started Model 6485 and 6487 User’s Manual Package content Model 6485 The following items are included with every Model 6485 order: • • • • • • • • • Model 6485 Picoammeter with line cord. Low Noise Cable with Male BNC on both ends (Model 4801). Protective BNC Shield/Cap (CAP-18). Banana lead to screw terminal adapter (Model CA-186-1B). Accessories as ordered. Certificate of calibration. Model 6485/6487 User Manual (P/N 6487-900-00).
Model 6485 and 6487 User’s Manual Getting Started 1-5 Model 4803 Low Noise Cable Kit — This cable kit includes: – – – 15m (50 ft) of low noise coax cable 10 male BNC connectors 5 female BNC chassis-mount connectors Model 7078-TRX-BNC adapter — 3-slot male triax to female BNC. Model 8607 — Banana cable set (1m). CA-186-1B — Banana lead to screw terminal adapter (one model CA-186-1B is included with every order).
1-6 Getting Started Model 6485 and 6487 User’s Manual be used with high performance test leads terminated with banana plugs, such as the Model 8607 High Performance Banana Cables. Model 8607 High Performance Banana Cables — Consists of two high voltage (1000V) banana cables. The cables are terminated with banana plugs that have retractable sheaths. CAP-31 Protective Shield /Cap — For use with 3-lug triax connectors.
Model 6485 and 6487 User’s Manual Getting Started 1-7 Rack mount kits Model 4288-1 single fixed rack mount kit — Mounts a single Model 6485/6487 in a standard 19-inch rack. Model 4288-2 side-by-side rack mount kit — Mounts two instruments (Models 182, 428, 486, 487, 2000, 2001, 2002, 2010, 2400, 2410, 2420, 2430, 6430, 6485, 6487, 6517A, 7001) side-by-side in a standard 19-inch rack. Model 4288-4 side-by-side rack mount kit — Mounts Model 6485/6487 and a 5.
1-8 Getting Started Model 6485 and 6487 User’s Manual Features The Model 6485/6487 is a high-performance picoammeter capable of measuring current (the Model 6487 also measures resistance). Section 2 contains details on its measurement capabilities (“Connection fundamentals,” page 2-2). Features of Model 6485/6487 Picoammeter include: • • • • • • • • • Setup storage — Five instrument setups (three user, GPIB defaults, and factory defaults) can be saved and recalled.
Model 6485 and 6487 User’s Manual Getting Started 1-9 Figure 1-1 Model 6485 front panel REM STEP SCAN CH1 TALK LSTN SRQ SHIFT FAST TIMER HOLD TRIG 5 CH2 MED CH3 SLOW CH4 CH5 REL FILT CH6 AUTO CH7 CH8 ERR CH9 BUFFER CH10 MATH REAR STAT 4W 6485 PICOAMMETER CONFIG/ LOCAL 1 MEDN MENU COMM AVG DISP MX+B TRIG M/X+B HALT LOG DIGITS REL ZCHK ZCOR RANGE AUTO RATE RANGE POWER SAVE SETUP STORE RECALL AZERO EXIT ENTER 34 2 klqb LIMIT 6 To modify a key’s properties,
1-10 Getting Started HALT DIGITS RATE and SAVE SETUP STORE RECALL LIMIT AZERO EXIT ENTER Model 6485 and 6487 User’s Manual Stops measurement process. Puts 6485 in idle state. Use to set display resolution. Use to select measurement rate. Use to control cursor position for making selections or editing values. Use to save present setup to a memory location. Use to restore setup to either GPIB or factory defaults, or to a user memory location.
Model 6485 and 6487 User’s Manual Getting Started 1-11 Model 6485 rear panel summary The rear panel of the Model 6485 is shown in Figure 1-2. Figure 1-2 Model 6485 rear panel 2 3 4 5 CAT II 6 7 MADE IN U.S.A.
1-12 Getting Started Model 6485 and 6487 User’s Manual 5 TRIGGER LINK Eight-pin micro-DIN connector for sending and receiving trigger pulses among connected instruments. Use a trigger link cable or adapter, such as Models 8501-1, 8501-2, 8502, and 8503. 6 RS-232 Female DB-9 connector for RS-232 operation. Use a straight-through (not null modem) DB-9 shielded cable. 7 IEEE-488 Connector for IEEE-488 (GPIB) operation. Use a shielded cable, such as Models 7007-1 and 7007-2.
Model 6485 and 6487 User’s Manual Getting Started 1-13 Model 6487 front and rear panel familiarization Model 6487 front panel summary The front panel of the Model 6487 is shown in Figure 1-3.
1-14 Getting Started OPER V-SOURCE V-SOURCE Model 6485 and 6487 User’s Manual Toggles the Vsource state (the Vsource state is displayed by an indicator). (Configured using the CONFIG >> OPER key sequence.) Increments voltage source value Decrements voltage source value 3 Operation keys COMM DISP TRIG LIMIT DIGITS RATE and 䊳 SAVE SETUP STORE RECALL AZERO DAMP EXIT ENTER Use to control and modify communication properties (GPIB or RS-232). Use to turn display on/off. Trigger measurement(s).
Model 6485 and 6487 User’s Manual Getting Started 7 Display annunciators * (asterisk) (more) AUTO BUFFER ERR FAST FILT LSTN MATH MED REL REM SLOW SRQ STAT TALK TIMER TRIG MON SCAN OCOMP Readings being stored in buffer. Indicates additional selections are available. Autorange enabled. Recalling readings stored in buffer. Questionable reading or invalid cal step. Fast (0.1 PLC) reading rate selected. MEDIAN and/or AVERAGE filter enabled (also DAMPING enabled). Instrument addressed to listen over GPIB.
Getting Started Model 6485 and 6487 User’s Manual Model 6487 rear panel summary The rear panel of the Model 6487 is shown in Figure 1-4. Figure 1-4 Model 6487 rear panel 2 1 3 4 5 6 7 8 MADE IN U.S.A.
Model 6485 and 6487 User’s Manual Getting Started 1-17 5 TRIGGER LINK Eight-pin micro-DIN connector for sending and receiving trigger pulses among connected instruments. Use a trigger link cable or adapter, such as Models 8501-1, 8501-2, 8502, and 8503. 6 DIGITAL I/O Male DB-9 connector for digital output lines and component handler signals. 7 RS-232 Female DB-9 connector for RS-232 operation. Use a straight-through (not null modem) DB-9 shielded cable.
1-18 Getting Started Model 6485 and 6487 User’s Manual Analog output The Model 6487 has an analog output on the rear panel. The ANALOG OUT provides a scaled, inverting ±2V output. A full-scale reading corresponds to ±2V output. See “Analog output,” page 2-14 in for full details on analog output operation. Digital I/O The Model 6487's Digital I/O port is a male DB-9 connector located on the rear panel. The four active-low, digital output lines and one input line are used to control external circuitry.
Model 6485 and 6487 User’s Manual Getting Started 1-19 Power-up Line power connection Follow the procedure below to connect the Model 6485/6487 to line power and turn on the instrument. 1. Check to see that the line voltage indicated in the window of the fuse holder assembly (Figure 1-2 or Figure 1-4) is correct for the operating voltage in your area.
1-20 Getting Started Model 6485 and 6487 User’s Manual Power-up sequence The following power-up sequence occurs when the Model 6485/6487 is turned on: 1. The Model 6485/6487 performs self-tests on its EPROM and RAM with all digits and annunciators turned on. (For the Model 6487 at power-up, the VOLTAGE SOURCE OPERATE LED will come on for 0.7 seconds to indicate that it is functional.) If a failure is detected, the instrument momentarily displays an error message and the ERR annunciator turns on.
Model 6485 and 6487 User’s Manual Getting Started 1-21 Default settings The Model 6485/6487 can be restored to one of five setup configurations: factory default (FACT), three user-saved (USR0, USR1, and USR2), and bus default (GPIB). As shipped from the factory, Model 6485/6487 powers up to the factory default settings. Factory default settings provide a general purpose setup for front panel operation, while the bus default (GPIB) settings do the same for remote operation.
1-22 Getting Started Model 6485 and 6487 User’s Manual Table 1-1 Model 6485 default settings Setting Factory (:SYStem:PRESet) GPIB (*RST) Trig Layer (CONF-TRIG): TRIG: Arm-In Source Event TRIG-IN IMM * * Arm Layer (CONF-ARM): Arm-In Source Event Arm Count Input Trigger Link Line Source Bypass Output Trigger Link Line Output Trigger IMM INF 1 NEVER 2 Off * 1 * * * * Buffer (STORE): Count Digital Filter (AVG): Count Type Disabled No effect Off 10 Moving * * * * * Display Resolution (DIGITS) For
Model 6485 and 6487 User’s Manual Getting Started 1-23 Table 1-1 (cont.) Model 6485 default settings Setting Factory (:SYStem:PRESet) GPIB (*RST) Rate: NPLC Rel: Rel Value (VAL) RS-232: All Settings Trigger Layer (CONF-TRIG): Trig-In Source Event Trigger Count Trigger Delay Input Trigger Link Line Source Bypass Output Trigger Link Line Slow 6.0 (60Hz) or 5.0 (50Hz) Off 0.
1-24 Getting Started Model 6485 and 6487 User’s Manual Table 1-2 Model 6487 default settings Factory Setting GPIB (:SYStem:PRESet) (*RST) Arm Layer (CONFIG ARM): Arm-In Source Event Arm Count Input Trigger Link Line Source Bypass Output Trigger Link Line Output Trigger Buffer (STORE): Count Damping (DAMP) Digital Filter (FILT): Count Type Display Resolution (DIGITS) Format byte order Function GPIB: Address Language IMM INF 1 NEVER 2 Off Disabled No effect On Off 10 Moving 5 -digits Swapped Amps No
Model 6485 and 6487 User’s Manual Getting Started Table 1-2 (cont.
1-26 Getting Started Model 6485 and 6487 User’s Manual Menu Many aspects of operation are configured through the menus summarized in Table 1-3 and Table 1-4. Refer to the section listed in the table for in-depth information. To access the menu, press the MENU key. Use the and RANGE keys to scroll through the menu items and the and 䊳 cursor keys to change options. Press ENTER to save any changes made and then leave the menu. Press EXIT to leave the menu without saving changes.
Model 6485 and 6487 User’s Manual Getting Started 1-27 Table 1-4 Model 6487 MENU structure Menu item Description Reference CAL Provides path to the following calibration submenu items: VOFFSET, COUNT, RUN, VSRC-RUN, DATES, UNLOCK, LOCK, and SAVE. Reference Manual Section 16 TSTAMP Timestamp format can be ABSolute or DELTa. Section 6 UNITS Readings can be displayed in ENGineering units or SCIentific notation. TEST Run display or key tests. SNUM Displays the unit’s serial number.
1-28 Getting Started Model 6485 and 6487 User’s Manual
Model 6485 and 6487 User’s Manual Connections 2-1 2 Connections • Connection fundamentals — Covers fundamental information about connecting test circuits to the picoammeter. • Basic connections to DUT — Details connecting test circuits to the picoammeter for current measurement and Model 6487 ohms measurements. • Using a test fixture — Discusses using general test fixtures as well as the Model 8009 test fixture.
2-2 Connections Model 6485 and 6487 User’s Manual Connection fundamentals The following provides important fundamental information on input connections to the Models 6485 and 6487. Typical connection drawings are provided in “Basic connections to DUT,” page 2-5. More detailed connections for specific measurements are in Section 3. Model 6485 connections Input connector The rear panel INPUT connector is a 2-lug female BNC connector (Figure 2-1).
Model 6485 and 6487 User’s Manual Connections 2-3 Figure 2-2 Model 6485 maximum input levels Input HI Max Continuous Input Signal * Input LO 42V Peak Chassis Ground * Maximum Continuous Input Signals 220V Peak, DC to 60Hz sine wave Low noise input cables When making precision measurements, you should always use low noise cables. As a general rule, always use the shortest possible cable for measurements. See “Model 6485 input cables, connectors, and adapters,” page 1-4 for recommended cables.
2-4 Connections Model 6485 and 6487 User’s Manual Voltage source output connectors The rear panel V-SOURCE OUTPUT HI and LO connectors (see Figure 1-4 in Section 1) are used to connect the voltage source to the DUT. The voltage source is primarily used for ohms measurements. See “Ohms measurement connections,” page 2-7 for details. Maximum input levels The maximum input levels to the Model 6487 are summarized in Figure 2-4.
Model 6485 and 6487 User’s Manual Connections 2-5 Basic connections to DUT Model 6485 DUT connections Connections Basic connections are shown in Figure 2-5, the DUT is the current to be measured. Circuit high is connected to the center conductor of the input connector and circuit low is connected to the connector’s shell.
2-6 Connections Model 6485 and 6487 User’s Manual t^okfkd The maximum safe voltage between picoammeter LO and chassis ground (common mode voltage) is 42V. The Model 6485 does not internally limit the LO-to-chassis voltage. Exceeding 42V can create a shock hazard.
Model 6485 and 6487 User’s Manual Connections 2-7 Figure 2-7 Basic Model 6487 current measurement connections 6487 HI DUT INPUT* LO * Maximum Continuous Input: 505V Peak t^okfkd If it is possible for the DUT or external supply to present more than 505V to the input HI, it is imperative that the connection between input LO and the external voltage source be sufficiently low impedance and capable of carrying the short-circuit current of the source, in order that the LO not exceed 505V.
2-8 Connections Model 6485 and 6487 User’s Manual Figure 2-8 Basic Model 6487 ohms connections 6487 HI INPUT* DUT LO LO V-SOURCE OUTPUT HI * Maximum Continuous Input: 505V Peak Noise and safety shields Figure 2-9 shows typical measurement shielding. In (A), a noise shield is used to prevent unwanted signals from being induced on the picoammeter input. Amps measurements below 1A may benefit from effective shielding. Typically, the noise shield is connected to picoammeter input LO.
Model 6485 and 6487 User’s Manual Connections 2-9 Figure 2-9 Shielding for Model 6487 measurements (unguarded) HI Metal Noise Shield Metal Noise Shield HI DUT INPUT Chassis Ground Metal Safety Shield DUT INPUT LO A. Noise Shield LO Safety Earth Ground B. Safety Shield Input voltage overload (OVRVOLT message) During normal operation, there should not be a significant voltage between the input HI and LO terminals of the Model 6485/6487.
2-10 Connections Model 6485 and 6487 User’s Manual General purpose test fixture Connections to a general purpose test fixture are shown in Figure 2-10 and Figure 2-11. This test fixture will accommodate a variety of connection requirements.
Model 6485 and 6487 User’s Manual Connections 2-11 Figure 2-11 General purpose test fixture connections to Model 6487 Metal Chassis To Voltage A Source Insulated Terminal Post (6) DUT To 6487 Input B To 6487 COMMON Metal Guard Plate Safety Earth Ground A Banana Jacks B 3-Lug Female Triax Connector on 6487. Model 8009 resistivity test fixture This test fixture allows volume resistivity in the range from 103 to 1018-cm and surface resistivity in the range from 103 to 1017/sq.
2-12 Connections Model 6485 and 6487 User’s Manual Model 6487 interlock The Model 6487 has a built-in interlock that works in conjunction with the voltage source. The interlock prevents the voltage source from being placed in operate on the 50V and 500V ranges, and optionally on the 10V range, to assure safe operation. Interlock connections Figure 2-13 shows interlock connections and the pin diagram of the INTERLOCK connector.
Model 6485 and 6487 User’s Manual Connections 2-13 Figure 2-13 Model 6487 interlock connections Model 6487 Test Fixture MADE IN U.S.A.
2-14 Connections Model 6485 and 6487 User’s Manual Analog output The Model 6485/6487 has an analog output on the rear panel. The ANALOG OUT provides a scaled, inverting ±2V output. A full-scale reading corresponds to ±2V output. `^rqflk Connecting COMMON or ANALOG OUT to earth while floating the input may damage the instrument. Connections for using this output are shown in Figure 2-14 (Model 6485) and Figure 2-15 (Model 6487). For a full-scale input (i.e. 2mA on the 2mA range), the output will be -2V.
Model 6485 and 6487 User’s Manual Connections 2-15 Measurement considerations There are a variety of factors to consider when making low-level measurements. These considerations are summarized in Table 2-1 and are detailed in Appendix C of the Model 6485 Instruction Manual and Appendix G of the Model 6487 Reference Manual, as well as in Appendix B of this manual.
2-16 Connections Model 6485 and 6487 User’s Manual Table 2-1 Summary of measurement considerations Considerations Description See Model 6485 Instruction Manual, Appendix C or Model 6487 Reference Manual, Appendix G for details. Input bias current Offset current of Model 6485/6487 could affect low current measurements. Voltage burden Offset voltage of Model 6485/6487 could cause errors if it is high in relation to the voltage of the measured circuit.
Model 6485 and 6487 User’s Manual Measurements and Sourcing Voltage 3-1 3 Measurements and Sourcing Voltage • Measurement overview — Explains the basic measurement and voltage source capabilities of Model 6485/6487. • Performance considerations — Covers warm-up period, voltage offset correction, auto zero, zero check, and zero correct. • Current measurements — Provides a basic procedure to measure current.
3-2 Measurements and Sourcing Voltage Model 6485 and 6487 User’s Manual Measurement overview Current measurements The basic current measurement capabilities of the Models 6485 and 6487 are summarized in Table 3-1. Accuracy for each measurement function and range is listed in the specifications (Appendix A).
Model 6485 and 6487 User’s Manual Measurements and Sourcing Voltage 3-3 Performance considerations Warm-up period The Model 6485/6487 can be used within one minute after it is turned on. However, the instrument should be turned on and allowed to warm up for at least one hour before use to achieve rated accuracy. If the instrument has been exposed to extreme temperatures, allow extra time for the internal temperature to stabilize.
3-4 Measurements and Sourcing Voltage Model 6485 and 6487 User’s Manual The Model 6485/6487 has a zero correct feature to algebraically subtract the voltage offset term from the measurement. Perform the following steps to algebraically zero correct the measurement: 1. 2. 3. 4. 5. 6. Enable zero check by pressing ZCHK. (For the Model 6485 “ZC” will be displayed; for the Model 6487, the “ZEROCHK” message will be displayed.
Model 6485 and 6487 User’s Manual Measurements and Sourcing Voltage 3-5 Current measurements Precautions Model 6485 precautions t^okfkd The maximum safe voltage between picoammeter LO and chassis ground (common mode voltage) is 42V. The Model 6485 does not internally limit the LO to chassis voltage. Exceeding 42V can create a shock hazard.
3-6 Measurements and Sourcing Voltage Model 6485 and 6487 User’s Manual Procedure Perform the following steps to measure current: Step 1. Select current function For the Model 6487, press the I| key to make sure the current function is selected. Step 2. Enable zero check Zero check should always be enabled before making connection changes. The ZCHK key toggles zero check on and off. Step 3.
Model 6485 and 6487 User’s Manual Measurements and Sourcing Voltage 3-7 Step 6. Disable zero check and take a reading from the display If the readings are noisy, you may want to use filtering to reduce noise. Filtering is covered in Section 4. Figure 3-1 Connections for Model 6485 current measurements Metal Noise Shield HI Input* Metal Safety Shield * 220V Peak 4801, 4802-10, or 4803 LO Safety Earth Ground CAT I MADE IN U.S.A.
Measurements and Sourcing Voltage Model 6485 and 6487 User’s Manual Figure 3-2 Connections for Model 6487 current measurements Red (HI) Metal Noise Shield Green (Chassis) Metal Safety Shield Safety Earth Ground Black (LO) 237-ALG-2 Cable MADE IN U.S.A.
Model 6485 and 6487 User’s Manual Measurements and Sourcing Voltage 3-9 Programming example — current measurements The following command sequence will perform one zero-corrected current measurement: *RST SYST:ZCH ON RANG 2e-9 INIT SYST:ZCOR:ACQ SYST:ZCOR ON RANG:AUTO ON SYST:ZCH OFF READ? ' ' ' ' ' ' ' ' ' ' ' Return 6485/6487 to GPIB defaults. Enable zero check. Select the 2nA range. Trigger reading to be used as zero correction. Use last reading taken as zero correct value. Perform zero correction.
3-10 Measurements and Sourcing Voltage Model 6485 and 6487 User’s Manual Step 2. Perform zero correction To achieve optimum accuracy for high resistance measurements, it is recommended that you zero correct the picoammeter before enabling the ohms function. To do so, make sure that zero check and the 2nA range are selected, then press the REL key to perform zero correction (MON indicator on). Step 3.
Model 6485 and 6487 User’s Manual Measurements and Sourcing Voltage Figure 3-3 Connections for Model 6487 ohms measurements Red (HI) Metal Noise Shield Green (Chassis) Metal Safety Shield DUT Safety Earth Ground 237-ALG-2 Cable Black (LO) DUT = Device Under Test. V-SOURCE OUTPUT MADE IN U.S.A.
3-12 Measurements and Sourcing Voltage Model 6485 and 6487 User’s Manual Programming example — ohms measurements The following command sequence will perform one zero-corrected resistance measurement: *RST FORM:ELEM READ,UNIT SYST:ZCH ON RANG 2e-9 INIT SYST:ZCOR:ACQ SYST:ZCOR ON RANG:AUTO ON SOUR:VOLT:RANG 10 SOUR:VOLT 10 SOUR:VOLT:ILIM 2.5e-3 SENS:OHMS ON SOUR:VOLT:STAT ON SYST:ZCH OFF READ? ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' Return 6487 to GPIB defaults. Measurement, units elements only.
Model 6485 and 6487 User’s Manual Measurements and Sourcing Voltage 3-13 Table 3-6 Voltage source current limits Source Range: Selectable Current Limit 10.0000V Range 25µA 250µA 2.5mA 50.000V Range 25µA 250µA 2.5mA 500.00V Range 25µA 250µA 2.5mA 25mA Sourcing voltage `^rqflk Do not connect external sources to the Model 6487 voltage source. External sources may damage the Model 6487 voltage source. Turning source on and off The OPER key will toggle the voltage source state (on/off).
3-14 Measurements and Sourcing Voltage Model 6485 and 6487 User’s Manual Open interlock indication If the interlock is asserted (opened) while the unit is on the 50V or 500V range, the voltage source will also technically be in compliance. However, there will be no indication of that status over the front panel or in the status registers. The open interlock takes precedence.
Model 6485 and 6487 User’s Manual Range, Units, Digits, Rate, and Filters 4-1 4 Range, Units, Digits, Rate, and Filters • Range, units, and digits — Provides details on measurement range, reading units, and display resolution selection. Includes the SCPI commands for remote operation. • Rate — Provides details on reading rate selection. Includes the SCPI commands for remote operation. • Model 6487 damping — Provides details on damping rate selection. Includes the SCPI command for remote operation.
4-2 Range, Units, Digits, Rate, and Filters Model 6485 and 6487 User’s Manual Range, units, and digits Range The ranges for current measurements are listed in Table 4-1. Table 4-1 Measurement ranges nA A mA 2nA 20nA 200nA 2A 20A 200A 2mA 20mA The full scale readings for every measurement range are 5% over range. For example, on the 20A range, the maximum input current is ± 21A. Input values that exceed the maximum readings cause the overflow message (OVRFLOW) to be displayed.
Model 6485 and 6487 User’s Manual Range, Units, Digits, Rate, and Filters 4-3 Units Readings can be displayed using engineering (ENG) units (i.e., 1.236 m) or scientific (SCI) notation (i.e., 1.236E-03). To change units, press the MENU key, select UNITS, then press ENTER. Select ENG or SCI, then press ENTER. klqb The units setting can only be changed from the front panel (no remote operation). Scientific notation provides more resolution on small values than engineering units.
4-4 Range, Units, Digits, Rate, and Filters Model 6485 and 6487 User’s Manual Rate The RATE key selects the integration time of the A/D converter, which is the period of time the input signal is measured. The integration time affects the amount of reading noise, as well as the ultimate reading rate of the instrument. The integration time is specified in parameters based on a number of power line cycles (NPLC), where 1 PLC for 60Hz is 16.67msec (1/60) and 1 PLC for 50Hz (and 400Hz) is 20msec (1/50).
Model 6485 and 6487 User’s Manual Range, Units, Digits, Rate, and Filters 4-5 Median filter The median filter is used to determine the "middle-most" reading from a group of readings that are arranged according to size. For example, assume the following readings: 20mA, 1mA, 3mA The readings are rearranged in an ascending order as follows: 1mA, 3mA, 20mA From the above readings, it is apparent that 3mA is the median (middle-most) reading.
4-6 Range, Units, Digits, Rate, and Filters Model 6485 and 6487 User’s Manual Filter control Model 6485 front panel control The median filter is turned on or off with the MEDN key. To configure the median filter, press CONFIG then MEDN, then select the desired rank (1-5) with the RANGE keys. The average filter is enabled or disabled with the AVG key. To control average filter parameters, press CONFIG then AVG, then select COUNT (2-100), and MOVING or REPEAT.
Model 6485 and 6487 User’s Manual Relative, mX+b, m/X+b (reciprocal), and log 5-1 5 Relative, mX+b, m/X+b (reciprocal), and log • • Relative — Explains how to null an offset or establish a baseline value. Includes the SCPI commands for remote operation. mX+b, m/X+b (reciprocal), and Logarithmic — Covers these three basic math operations and includes the SCPI commands for remote operation.
5-2 Relative, mX+b, m/X+b (reciprocal), and log Mode 6485 and 6487 User’s Manual Relative Relative (Rel) nulls an offset or subtracts a baseline reading from present and future readings. When a Rel value is established, subsequent readings will be the difference between the actual input and the Rel value. Displayed (Rel’ed) Reading = Actual Input - Rel Value A Rel value is the same for all measurement ranges. For example, a Rel value of 1E-6 is 1A on the 2A range.
Model 6485 and 6487 User’s Manual Relative, mX+b, m/X+b (reciprocal), and log 5-3 Programming example — relative This program fragment establishes a 1A baseline for measurements: CALC2:NULL:OFFS 1e-6 CALC2:NULL:STAT ON SYST:ZCH OFF INIT CALC2:DATA? ' ' ' ' ' Set Rel value of 1A. Enable Rel. Turn off zero check. Trigger reading. Request Rel’ed reading.
5-4 Relative, mX+b, m/X+b (reciprocal), and log Mode 6485 and 6487 User’s Manual Configuring math functions Model 6485 To select and configure math functions from the Model 6485 front panel, press either the MX+B or M/X+B key, then enter the required m, b, and units parameters. Use MX+B or M/X+B to toggle math on or off. The MATH annunciator will turn on to indicate that the math function is enabled.
Model 6485 and 6487 User’s Manual Buffer and Sweeps 6-1 6 Buffer and Sweeps • Buffer operations — Explains how to store and recall readings including buffer statistics. • Model 6487 voltage sweeps — Discusses how to generate sweeps using the voltage source.
6-2 Buffer and Sweeps Model 6485 and 6487 User’s Manual Buffer operations The Model 6485 has a buffer to store from one to 2,500 readings. The Model 6487 buffer can store from one to 3,000 readings. Both instruments also store overflow readings and a timestamp, and each Model 6487 reading includes the voltage source value. The timestamp for each reading is referenced to the time the measure/store process is started.
Model 6485 and 6487 User’s Manual Buffer and Sweeps 6-3 Buffer timestamp To change the buffer timestamp format, press MENU, select TSTAMP, then press ENTER. Select the desired option: ABS (absolute) or DELT (delta). For ABS, each timestamp is referenced to the first reading stored in the buffer. The first reading always has a timestamp of 0000000.0000. With DELT, each timestamp provides the time between the readings.
6-4 Buffer and Sweeps klqb Model 6485 and 6487 User’s Manual If any readings stored in the buffer are the result of an overflow or Model 6487 overvoltage condition, the buffer statistics calculation will not be performed. Buffer recall via front panel operation will show a series of dashes in place of the requested buffer statistics value. In remote operation, the corresponding buffer statistics will be represented by the value +9.91e37.
Model 6485 and 6487 User’s Manual Buffer and Sweeps 6-5 Model 6487 voltage sweeps The Model 6487 voltage source can be used to generate voltage sweeps from a start voltage to a stop voltage at discrete step voltages. The Model 6487 stores readings in the buffer for later recall, one set of readings per voltage step. Front panel sweeps To generate sweeps from the front panel, press CONFIG then OPER, select SWEEP, then press ENTER.
6-6 Buffer and Sweeps Model 6485 and 6487 User’s Manual Programming example The following command sequence performs a sweep from 1V to 10V in 1V increments: *RST SOUR:VOLT:SWE:STAR 1 SOUR:VOLT:SWE:STOP 10 SOUR:VOLT:SWE:STEP 1 SOUR:VOLT:SWE:DEL 0.1 ARM:COUN 10 FORM:ELEM READ,VSO SOUR:VOLT:SWE:INIT SYST:ZCH OFF INIT TRAC:DATA? ' ' ' ' ' ' ' ' ' ' ' Return 6487 to RST defaults. Start voltage = 1V. Stop voltage = 10V. Step voltage = 1V. 0.1s delay. Reset arm count. Select reading, voltage source data.
Model 6485 and 6487 User’s Manual Remote Operation and Commands 7-1 7 Remote Operation and Commands • Selecting and configuring an interface — Explains how to select and configure an interface: GPIB or RS-232. • Remote commands — Lists the following types of bus commands: general bus commands, common commands, signal oriented commands, and SCPI command subsystems.
7-2 Remote Operation and Commands Model 6485 and 6487 User’s Manual Selecting and configuring an interface Interfaces The Model 6485/6487 supports two built-in remote interfaces: GPIB interface and RS-232 interface. You can use only one interface at a time. At the factory, the GPIB is selected. To select the interface, press COMM, select RS 232 or GPIB, then press ENTER. The Model 6485/6487 will reset with the new interface selected.
Model 6485 and 6487 User’s Manual Remote Operation and Commands Figure 7-1 Model 6485 IEEE-488 and RS-232 connector locations RS-232 IEEE-488 CAT I MADE IN U.S.A. IEEE-488 (CHANGE IEEE ADDRESS WITH FRONT PANEL MENU) ANALOG OUT INPUT TRIGGER LINK ! RS-232 LINE RATING 50, 60Hz 30 VA FUSE LINE 400mAT (SB) 100 VAC 120 VAC 200mAT (SB) 220 VAC 240 VAC 120 220V PK Figure 7-2 Model 6487 IEEE-488 and RS-232 connector locations RS-232 IEEE-488 MADE IN U.S.A.
7-4 Remote Operation and Commands Model 6485 and 6487 User’s Manual Front panel GPIB operation Error and status messages See Appendix B in the Model 6485 Instruction Manual or Model 6487 Reference Manual for a list of error and status messages associated with IEEE-488 programming. GPIB status indicators REM shows when the instrument is in the remote state, TALK is on when the instrument is in the talker active state, and LSTN is on when the Model 6485/6487 is in the listener active state.
Model 6485 and 6487 User’s Manual Remote Operation and Commands 7-5 Common commands Common commands are summarized in Table 7-2. Table 7-2 IEEE-488.2 common commands and queries Mnemonic *CLS *ESE *ESE? *ESR? *IDN? Name Description Clear status Event enable command Event enable query Event status register query Identification query Clears all event registers and error queues. Program the standard event enable register. Read the standard event enable register.
7-6 Remote Operation and Commands Model 6485 and 6487 User’s Manual SCPI command subsystems Table 7-4 summarizes the various SCPI subsystems used to program most Model 6485/ 6487 operations. Detailed lists of commands associated with these subsystems are located in Section 14 of the Model 6485 Instruction Manual or Model 6487 Reference Manual.
Model 6485 and 6487 User’s Manual Remote Operation and Commands 7-7 The query command requests the presently programmed status. It is identified by the question mark (?) at the end of the fundamental form of the command. Most commands have a query form. Each program message must be terminated with an LF (line feed), EOI (end or identify), or an LF+EOI. Each response is terminated with an LF (line feed) and EOI (end or identify).
7-8 Remote Operation and Commands Model 6485 and 6487 User’s Manual
Model 6485 and 6487 User’s Manual Specifications A-1 A Specifications
6485 Picoammeter Specifications 5¹⁄₂ DIGIT ACCURACY (1YR) 1 DEFAULT ±(% RDG. + OFFSET) RANGE RESOLUTION 18°–28°C, 0–70% RH 2 nA 10 fA 0.4 % + 400 fA 20 nA 100 fA 0.4 % + 1 pA 200 nA 1 pA 0.2 % + 10 pA 2 μA 10 pA 0.15% + 100 pA 20 μA 100 pA 0.1 % + 1 nA 200 μA 1 nA 0.1 % + 10 nA 2 mA 10 nA 0.1 % + 100 nA 20 mA 100 nA 0.1 % + 1 μA TYPICAL RMS NOISE 2 20 fA 100 fA 1 pA 10 pA 100 pA 1 nA 10 nA 100 nA TEMPERATURE COEFFICIENT: 0°–18°C & 28°–50°C. For each °C, add 0.1 × (% rdg + offset) to accuracy spec.
6487 Picoammeter Specifications 5¹⁄₂ DIGIT ACCURACY (1YR) 1 DEFAULT ±(% RDG. + OFFSET) RANGE RESOLUTION 18°–28°C, 0–70% RH 2 nA 10 fA 0.3 % + 400 fA 20 nA 100 fA 0.2 % + 1 pA 200 nA 1 pA 0.15 % + 10 pA 2 μA 10 pA 0.15% + 100 pA 20 μA 100 pA 0.1 % + 1 nA 200 μA 1 nA 0.1 % + 10 nA 2 mA 10 nA 0.1 % + 100 nA 20 mA 100 nA 0.
A-4 Specifications Model 6485 and 6487 User’s Manual
Model 6485 and 6487 User’s Manual General Measurement Considerations B-1 B General Measurement Considerations • Measurement considerations — lists and defines nine types of measurement considerations.
B-2 General Measurement Considerations Model 6485 and 6487 User’s Manual Measurement considerations The following measurement considerations apply to all precision measurements. Table 2-1 lists all measurement considerations and indicates where to find detailed information on them. For additional measurement considerations, see Appendix C of the Model 6485 Instruction Manual or Appendix G of the Model 6487 Reference Manual.
Model 6485 and 6487 User’s Manual General Measurement Considerations B-3 this purpose, measuring instruments should be placed on their lowest ranges. The configuration that results in the lowest noise signal is the one that should be used. A convenient way to make this connection uses the ground link at the rear of the Model 6485/6487.
B-4 General Measurement Considerations Model 6485 and 6487 User’s Manual Electrochemical effects Error currents also arise from electrochemical effects when ionic chemicals create weak batteries on a circuit board. These batteries could generate a few nanoamps of current between conductors. Ionic contamination may be the result of body oils, salts, or solder flux. The problem is further enhanced by high humidity (moisture) that decreases insulation resistance.
Model 6485 and 6487 User’s Manual General Measurement Considerations B-5 Electrostatic interference is first recognizable when hand or body movements near the experiment cause fluctuations in the reading. Pick-up from AC fields can also be detected by observing the picoammeter analog output on an oscilloscope. Line frequency signals on the output are an indication that electrostatic interference is present. Means of minimizing electrostatic interference include: 1. 2. Shielding.
B-6 General Measurement Considerations Model 6485 and 6487 User’s Manual The effect on instrument performance can be considerable if enough of the unwanted signal is present. The effects of EMI can be seen as an unusually large offset or, in the case of impulse sources, erratic variations in the displayed reading. The instrument and experiment should be kept as far away as possible from any EMI sources.
Model 6485 and 6487 User’s Manual Example Programs C-1 C Example Programs • Programming examples — lists and defines three types of programming examples.
C-2 Example Programs Model 6485 and 6487 User’s Manual Programming examples This section contains example programs (pseudo-code) to achieve speed and buffer size specifications. 1000 readings/second into internal buffer klqb This program configures the Model 6485/6487 to 0.01 PLC, digital filters off, front panel off, auto-zero off, as well as takes and stores 2000 readings. *RST TRIG:DEL 0 TRIG:COUN 2000 NPLC .01 RANG .
Model 6485 and 6487 User’s Manual Example Programs C-3 900 readings/second to IEEE-488 bus This program uses multiple reading queries to get high speed measurements over the bus in real time. To improve continuity of readings, reduce the trigger count. To improve throughput, increase the trigger count. klqb This program configures the Model 6485/6487 to 0.01 PLC, digital filters off, front panel off, auto-zero off, binary transfer, and IEEE-488.1 (language). Model 6485/6487 must be set to IEEE-488.
C-4 Example Programs Model 6485 and 6487 User’s Manual 3000 readings into internal buffer klqb This program is for the Model 6487 only. Due to memory limitations, the maximum product of the trigger count times the arm count is 2,048. Consequently, two triggers are required to completely fill the buffer to its 3,000 reading maximum. See Section 7 of the Model 6487 Reference Manual for triggering details. *RST TRIG:DEL 0 TRIG:COUN 1500 NPLC .01 RANG .
7.5X9BackCovr 12-06.qxd 1/10/07 2:45 PM Page 1 Specifications are subject to change without notice. All Keithley trademarks and trade names are the property of Keithley Instruments, Inc. All other trademarks and trade names are the property of their respective companies. A G R E A T E R M E A S U R E O F C O N F I D E N C E Keithley Instruments, Inc. Corporate Headquarters • 28775 Aurora Road • Cleveland, Ohio 44139 • 440-248-0400 • Fax: 440-248-6168 • 1-888-KEITHLEY • www.keithley.
