KEITHLEY 220 (01) PDF Document

The following safety precautions should be observed before using the KEITHLEY 220 and any associated instrumentation:

• 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. Read the operating information carefully before using the product.

• Exercise extreme caution when a shock hazard is present. Lethal voltage may be present on cable connector jacks or test fixtures. A shock hazard exists when voltage levels greater than 30V RMS, 42.4V peak, or 60VDC are present.

• Users of this product must be protected from electric shock at all times. The responsible body must ensure that users are prevented access and/or insulated from every connection point.

• Before operating the KEITHLEY 220, make sure the line cord is connected to a properly grounded power receptacle. Inspect the connecting cables, test leads, and jumpers for possible wear, cracks, or breaks before each use.

• 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, or making internal changes.

• 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. Always make measurements with dry hands while standing on a dry, insulated surface.

• The instrument and accessories must be used in accordance with its specifications and operating instructions or the safety of the equipment may be impaired.

• Do not exceed the maximum signal levels of the instruments and accessories.

• When fuses are used, replace with the same type and rating for continued protection against fire hazard.

• To clean the KEITHLEY 220, use a damp cloth or mild, water-based cleaner. Clean the exterior of the instrument only. Do not apply cleaner directly to the instrument or allow liquids to enter or spill on the instrument.

MODEL 220 CURRENT SOURCE

OUTPUT RESISTANCE: >10¹⁴Ω (on 1nA range).

OUTPUT CAPACITANCE: <20pF.

LINE REGULATION: <0.01% for AC power line changes within specified limits.

VOLTAGE LIMIT: Bipolar, 1V to 105V in 1V programmable steps.

RESPONSE TIME: <3ms to within 0.1% of programmed change.

TRANSIENT RECOVERY TIME: <3ms to rated accuracy following any change in compliance voltage.

GUARD OUTPUT:
Maximum Load Capacitance: 10nF.
Maximum Load Current: Absolute total (Output + Guard) not to exceed 105mA.
Accuracy: ±1mV (excluding output lead voltage drop).

PROGRAM MEMORY:
Number of Locations: 100.
Range of Dwell Times: 3ms to 999.9s.
Accuracy of Dwell Time: ±(0.05%+200μs).

OUTPUT LOAD: Output load must be non-inductive.

EXTERNAL TRIGGER: TTL-compatible EXTERNAL TRIGGER INPUT and OUTPUT.

OUTPUT CONNECTIONS: Teflon® insulated 2-lug triax connector for output; five-way binding posts for GUARD, OUTPUT COMMON, and CHASSIS; BNC (chassis isolated) connectors for EXTERNAL TRIGGER INPUT and OUTPUT; Amphenol or Cinch Series 87 IEEE and printed circuit digital I/O port. All connections on rear panel.

IEEE-488 BUS IMPLEMENTATION

MULTILINE COMMANDS: DCL, LLO, SDC, GET, GTL, UNT, UNL, SPE, SPD.

UNILINE COMMANDS: IFC, REN, EOI, SRQ, ATN.

INTERFACE FUNCTIONS: SH1, AH1, T6, TEO, L4, LEO, SR1, RL1, PP0, DC1, DT1, C0, E1.

INTERNAL PROGRAMMABLE PARAMETERS: Display Mode, Output, Prefix Data Format, EOI, SRQ (including mask for over Limit), Program Mode, Range, Trigger Mode, Terminator Character, Inputs (Source, Limit, Dwell Time, 100-Point Memory Locations), Output Status, Digital Self Test.

DIGITAL I/O PORT: A separate I/O port consisting of four input and four output lines as well as common (IEEE-488) and +5V DC. Outputs will drive one TTL load. Inputs represent one TTL load. The KEITHLEY 220 can be programmed to generate an “SRQ” upon any change in the four bit input data. Mating connector supplied.

GENERAL

DISPLAY: 0.5 in LED digits, 4½-digit signed mantissa, 1-digit signed exponent.

SYSTEMS COMPATIBILITY: IEEE-488-1978.

LIMIT INDICATIONS (Voltage Limit): “V-LIMIT” LED will blink.

MAXIMUM ALLOWABLE COMMON MODE VOLTAGE (OUTPUT or OUTPUT COMMON to CHASSIS): 250V rms, DC to 60Hz.

SELF TEST: Digital RAM, ROM, front panel LEDs upon power ON.

EMC: Conforms to European Union Directive 89/336/EEC.

SAFETY: Conforms to European Union Directive 73/23/EEC (meets EN61010-1/IEC 1010).

WARM-UP: 1 hour to rated accuracy.

POWER: 105-125 or 210-250V AC (internal switch selected), 50 or 60Hz, 60W maximum (80VA maximum). 90-105 or 180-210V AC operation available.

COOLING: Internal fan for forced air cooling.

ENVIRONMENTAL LIMITS: Operating: 0°-50°C; up to 35°C at 70% non-condensing relative humidity. Storage: -25° to 70°C.

DIMENSIONS, WEIGHT: 127mm high x 216mm wide x 359mm deep (5 in x 8½ in x 14¼ in). Net weight 4.4kg (9 lb 11 oz).

ACCESSORIES SUPPLIED: Model 6011 Triaxial Test Lead (3 ft).

The KEITHLEY 220 is inspected both mechanically and electrically before shipment. Upon receiving the KEITHLEY 220, unpack all items from the shipping container and check for any obvious damage that may have occurred during transit. Report any damage to the shipping agent. Retain and use the original packaging materials if reshipment is necessary. The following items are shipped with all KEITHLEY 220 orders:

• Model 220 Programmable Current Source

• Model 220 Instruction Manual

• Model 6011 Triaxial Test Lead

• Model 220/230 Programming Manual

• Optional accessories per request.

The KEITHLEY 220 should be packed in its original carton using the specified packaging method. Before packaging, wrap the instrument in plastic. After it is placed in the box, surround the instrument with styrofoam packaging material.

Plug the KEITHLEY 220 into the proper power receptacle in accordance with the line voltage setting table. Ground the instrument through a properly earth grounded receptacle before operation. Failure to ground the instrument can result in severe injury or death in the event of short circuit or malfunction.

Immediately after turning on the KEITHLEY 220 via the power switch, the display will indicate the following for several seconds:

1. A display test is performed. The operator can note inoperative display segments. In addition, the push button and the TALK, LISTEN, REMOTE indicators will light simultaneously if operating correctly.

2. After the display test is complete, the KEITHLEY 220 will display the software revision level for approximately one second.

3. After the software revision level is displayed, the KEITHLEY 220 will display the primary address of the instrument for approximately one second. The primary address is factory set at 12.

*For instruments equipped with low voltage transformer TR-187.

The KEITHLEY 220 has four operating functions in the display group:

• SOURCE button: Selects the source data for display. The full scale range of the available source current is 1.9995nA to 101.00mA. The source current is displayed as a 4½ digit number with a single digit exponent. The least significant digit is truncated to a “0” or a “5” when the ENTER button is pressed. During data entry, pressing the SOURCE button reverts the display to the previous source data.

• V-LIMIT button: Selects the voltage compliance for display, ranging from 1V to 105V in 1V increments. The voltage compliance is displayed as a three digit number. The voltage compliance limiting is bipolar. During data entry, pressing the V-LIMIT button reverts the display to the previous V-limit data.

• DWELL TIME button: Selects the dwell time data for display, ranging from 3msec to 999.9sec. Dwell time is the programmed time the KEITHLEY 220 spends on a specific memory location in single or continuous program modes. During data entry, pressing the DWELL TIME button reverts the display to the previous dwell time data.

• MEMORY button: Selects the present memory location number for display, from 1 to 100. Each memory location contains source current data, V-limit data, and dwell time data. During data entry, pressing the MEMORY button reverts the display to the previously displayed memory location.

The data entry group on the KEITHLEY 220 consists of three buttons:

• EXPONENT button: Allows entry of exponent data onto the display. This button is active only in the source and dwell time display modes.

• ENTER button: Loads the displayed data into the present memory location.

• COPY button: Duplicates the source, V-limit, and dwell time data from one memory location into the next memory location. This button is active only in the memory display mode.

The 12 buttons in the Data group allow entry of numerical data from 0 to 9, including a decimal point and polarity.

The program mode group on the KEITHLEY 220 consists of three buttons that select the mode of scanning the internal 100 memory locations:

• STEP button: Selects the step program mode. This allows the user to manually step through the programmed memory locations using the START/STOP button. When in step program mode, the STEP LED is turned on.

• SINGLE button: Selects the single program mode. This mode cycles through the programmed memory locations one time upon actuation of the START/STOP button. When in single program mode, the SINGLE LED is turned on.

• CONTINUOUS button: Selects the continuous program mode. This mode cycles through the programmed memory locations continuously upon actuation of the START/STOP button. When in continuous program mode, the CONTINUOUS LED is turned on.

The program control group on the KEITHLEY 220 consists of two buttons:

• RESET button: A momentary control that sets the presently displayed memory location back to memory location 1. If the KEITHLEY 220 is in operate mode, pressing RESET sets the output to the source data in memory location 1. Pressing RESET during data entry reverts the display to the previously displayed data. After data is entered and the ENTER button is pressed, pressing RESET reverts the instrument back to the conditions in memory location 1.

• START/STOP button: An alternate action control with two functions:
1. When pressed, it initiates the selected program mode (step, single, or continuous).
2. When pressed a second time, it stops the action of the selected program mode.
The START/STOP LED will be on continuously during the execution of the single or continuous program mode. In step program mode, the LED will be on for the duration of the programmed dwell time.

• OUTPUT Connector: A Teflon® insulated female triax connector.

• GUARD terminal: Provides a low impedance voltage source which is equal to the output compliance voltage. The maximum load capacitance is 0.01 µF, and the maximum load current (guard and output) is not to exceed 105mA.

• OUTPUT COMMON terminal: Provides easy access to output common, which is also the inner shield of the output connector.

• CHASSIS GROUND terminal: Provides a convenient connection to chassis ground (earth ground).

• IEEE-488 INTERFACE connector: Provides bus connection to the KEITHLEY 220.

• ADDRESS switches: Used to program the primary address for the IEEE-488 interface bus operation.

• DIGITAL I/O port: Consists of four input and four output lines, as well as IEEE-488 common and +5VDC.

• EXTERNAL TRIGGER INPUT: Initiates the selected program mode in the same manner as the START/STOP button upon receiving a TTL level negative transition.

• EXTERNAL TRIGGER OUTPUT: Provides a negative TTL level pulse at the completion of the programmed dwell time.

Upon power up or actuation of the RESET button, the KEITHLEY 220 is set to memory location 1. Follow these steps for general operation:

1. Turn on the KEITHLEY 220 and allow one hour for warm-up for rated accuracy.

2. Select memory location:
A. Press MEMORY.
B. Press the number(s) of the desired memory location (1 to 100).
C. Press ENTER.

3. Program the desired source:
A. Press SOURCE.
B. Press the number(s) for the desired source current (.0000-9mA to 101.00mA).
C. Press ENTER.

4. Program the appropriate V-limit:
A. Press V-LIMIT.
B. Press the number(s) for the appropriate compliance voltage limit (1 to 105V in one volt increments).
C. Press ENTER.

5. Program the desired dwell time:
A. Press DWELL TIME.
B. Press the number(s) for the appropriate dwell time (3msec to 999.9sec in 1msec increments).
C. Press ENTER.

6. Select the desired program mode (step, single or continuous).

7. Connect an appropriate non-inductive load.

8. Program the Output to the operate mode by pressing the OUTPUT button.

9. Select the program control by pressing the START/STOP button.

The KEITHLEY 220 will display an error message (“Err”) if it is programmed into a parameter value that is outside of the instrument’s range. After displaying the error for approximately one second, the instrument returns to the previous display. The conditions that cause an error message are listed below.

Use the following procedure to program the KEITHLEY 220 to output 10mA with a 10V compliance limit:

1. Select a memory location, if memory location 1 is not desired.

2. Press SOURCE, 1, 0, EXPONENT, 3, ENTER. (This programs a source value of 10mA.)

3. Press V-LIMIT, 1, 0, ENTER. (This programs a 10V V-Limit.)

4. Connect the load.

5. Press OPERATE.

Note: If the ENTER button is not pressed in the sequence indicated, the display data will not be programmed into the appropriate memory location.

The KEITHLEY 220 can fabricate output waveforms with up to 100 individual steps. The following is an example procedure for outputting a 10mA to 2mA square wave at 100Hz with a V-limit of 10V. Before starting, cycle power to the instrument to clear previously programmed memory locations.

1. Press MEMORY, 1, ENTER. (Selects memory location 1.)

2. Press SOURCE, 1, 0, EXPONENT, 3, ENTER. (Programs memory location 1’s source for 10mA.)

3. Press V-LIMIT, 1, 0, ENTER. (Programs memory location 1’s V-limit for 10V.)

4. Press DWELL TIME, 5, EXPONENT, 3, ENTER. (Programs memory location 1 dwell time for 5msec.)

5. Press MEMORY, 2, ENTER. (Selects memory location 2.)

6. Press SOURCE, 2, EXPONENT, 3, ENTER. (Programs memory location 2 source for 2mA.)

7. Press V-LIMIT, 1, 0, ENTER. (Programs memory location 2 V-limit for 10V.)

8. Press DWELL TIME, 5, +/-, EXPONENT, 3, ENTER. (Programs memory location 2 dwell time for 5msec.)

9. Press CONTINUOUS, OPERATE, START/STOP.

Upon completion of step 9, the KEITHLEY 220 will output a 10mA to 2mA 100Hz square wave. When fabricating waveforms, observe the response time specifications and consider the effect of load impedance.

External Trigger Input: The external trigger input initiates the program mode (single, continuous, or step) in the same manner as the START button. To output any programmed values, the program mode must be selected, the OPERATE button enabled, and the instrument must receive the external trigger input pulse.

External Trigger Output: The external trigger output is a pulse signifying the completion of a programmed dwell time. The pulse is present at the external trigger output in any of the three program modes.
• For single or continuous modes, there is an output pulse at the end of every programmed dwell time.
• For step mode, there is an output at the end of the programmed dwell time for one memory location. To advance to the next step, another external trigger input pulse is required.

Leakage resistance between low current conductors and nearby voltage sources can cause significant error currents. Guarding eliminates such stringent insulation requirements by surrounding the sensitive input with a conductor (the guard) connected to a low impedance point which is at the same potential.

The GUARD terminal on the rear panel of the KEITHLEY 220 provides an easy connection to a low impedance voltage source which is equivalent to the output compliance voltage. The maximum load capacitance for the guard output is 0.01µF, and the maximum load current (including guard and output) is not to exceed 105mA. The accuracy of the guard is ±1mV, excluding output lead I•R voltage drop.

Before beginning, ensure the KEITHLEY 220 has warmed up for one hour. Verification should be performed by qualified personnel.

1. Connect the KEITHLEY 220, a Model 192 DMM, and a 100Ω load resistor as per the test setup diagram.

2. Select the 20VDC range on the Model 192.
a. Program the KEITHLEY 220 to output +00.00-3. Verify that the reading on the Model 192 does not exceed +5mV.
b. Program the KEITHLEY 220 to output +0.0000-3. Verify that the reading on the Model 192 does not exceed +1mV.
c. Select the 2V range on the Model 192. Program the KEITHLEY 220 to output +.0000-3. Verify that the reading on the Model 192 does not exceed +100µV. Select the 20V range on the Model 192.

3. Program the KEITHLEY 220 for 50mA with a 20V compliance limit. Note: Because of power constraints on the 1/4W resistor, only apply power momentarily to prevent overheating.

4. Press the OPERATE button on the KEITHLEY 220.

5. Verify that the reading on the Model 192 display is within the limits specified in the verification table.

6. Repeat steps 2 through 5 for the 10mA and 1mA ranges.

7. Repeat steps 2 through 6 with negative output current.

*Includes test equipment tolerances.

**Apply momentarily to prevent the resistor from overheating.

If power fails, first verify that the fuse (F101) is not defective. The fuse is accessible from the rear panel. To prevent a shock hazard, always turn the instrument off and disconnect the line cord before replacing the fuse.

1. Turn power off and disconnect the line cord.

2. The fuse carrier is spring loaded. Using a slotted screwdriver, push the fuse carrier in and rotate it ¼-turn counter-clockwise. The carrier and fuse will eject from the holder.

3. Remove the fuse from the carrier and replace it with the correct type and rating as specified in the tables below. Do not install a fuse with a higher rating than specified.

4. To install the new fuse and carrier into the holder, reverse the procedure in step 2.

*Requires special factory installed transformer TR-187.

*Requires special factory installed transformer TR-187.

To prevent a shock hazard, turn the KEITHLEY 220 off, disconnect the line cord, and remove all test leads before changing the line voltage setting.

1. Remove the top cover.

2. Refer to the table below and set switch S102 (located near the transformer, underneath the IEEE-488 interface board) accordingly.

3. Install the proper fuse as per the fuse replacement procedure.

Note: The line voltage setting is marked on the rear panel. If the range is changed, the box next to the selected line voltage should be appropriately marked as an external reminder.

*Requires special factory installed transformer TR-187.

The internal fan on the KEITHLEY 220 has an air filter to keep the instrument relatively free of dust and dirt. This filter must be kept clean for optimum performance and to prevent overheating. To clean the filter:

1. Remove the filter from the fan.

2. Use compressed air to remove the dust and dirt. If the filter is excessively dirty, wash it in mild soap and water and dry it with compressed air.

3. Reinstall the filter.

Upon power-up, the KEITHLEY 220 performs a digital self-test of the RAM and a cyclic redundancy check (CRC) of the ROM. If the self-test or CRC reveals a problem with any of the memory chips, the KEITHLEY 220 will display a flashing error message corresponding to the defective chip. For example, if RAM chip number four is defective, the display will flash “14444 4”. This informs the operator that RAM chip number four is defective.

To check the power supply, ensure the KEITHLEY 220 is turned on, the correctly rated fuse F101 has continuity, and the line selector switch S102 is in the correct position. Then, check the following conditions:

*Referenced to output common.

**Referenced to analog common.

***Referenced to digital common.