Type: Bipolar, 4-quadrant, DC current source
Current generation: Fully linear regulation with digital setting and analog control
Current range: ±70 A
Compliance voltage (DC) : ±35 V nominal
Power: 2450 W nominal
Load resistance range: 0.4 Ω to 0.6 Ω
Load inductance range: 0 to 1 H
Nominal load: 0.5 Ω, 0.5 H
Current ripple: 5 mA RMS (0.007%) at 70 A into nominal load
Current ripple frequency: Dominated by the line frequency and its harmonics
Temperature coefficient: ±15 ppm of full scale/°C
Line regulation: ±60 ppm of full scale/10% line change
Stability (1 h): 1 mA/h (after warm-up)
Stability (24 h): 5 mA/24 h (typical, dominated by temperature coefficient and line regulation)
Isolation: Differential output is optically isolated from chassis to prevent ground loops
Slew rate: 50 A/s into nominal load, 650 A/s minimum into a resistive load
Compliance voltage (AC): ±43 V nominal
Setting time: <1 s for 10% step to within 1 mA of output into nominal load
Modulation response: 0.17 Hz at ±70 A sine wave into nominal load, <0.02% THD; 10 Hz at ±10 A sine wave into nominal load, <0.10% THD
Attenuation: -0.5 dB at 10 Hz
Protection: Short circuit, line loss, low line voltage, high line voltage, output over voltage, output over current, and over temperature
Connector: Two lugs with 6.4 mm (0.25 in) holes for M6 or 0.25 in bolts

Output programming

Internal current setting

Resolution: 0.1 mA (20-bit)
Settling time: 600 ms for 1% step to within 1 mA (of internal setting)
Accuracy: ±10 mA ±0.05% of setting
Operation: Keypad, computer interface
Protection: Programmable current setting limit

Internal current ramp

Ramp rate: 0.1 mA/s to 99.999 A/s (complaince limited)
Update rate: 23.7 increments/s
Ramp segments: 5
Operation: Keypad, computer interface
Protection: Programmable ramp rate limit

External current programming

Sensitivity: 10 V/70 A
Resolution: Analog
Accuracy: ±10 mA ±1% of setting
Input resistance: 20 kΩ
Operation: Voltage program through rear panel, can be summed with internal current setting
Limits: Internally clamped at ±10.1 V and bandwidth limited at 40 Hz to protect output
Connector: Shared 15-pin D-sub


Output current

Resolution: 0.1 mA
Accuracy: ±5 mA ±0.05% of reading
Update rate: 2.5 rdg/s display, 10 rdgs/s interface

Output voltage (at supply terminals)

Resolution: 1 mV
Accuracy: ±5 mV ±0.05% of rdg
Update rate: 2.5 rdg/s display, 5 rdg/s interface

Front panel

Display type: 8-line by 40-character, graphic vacuum fluorescent module
Display readings: Output current, output voltage, and internal water temperature
Display settings: Output current and ramp rate
Display annunciators: Status and errors
LED annunciators: Fault, Compliance, Power Limit, Ramping, Remote
Audible annunciator: Errors and faults
Keypad type: 26 full-travel keys
Keypad functions: Direct access to common operations, menu driven setup
Power: White flush ON and black extended OFF push buttons




Features: SH1, AH1, T5, L4, SR1, RL1, PP0, DC1, DT0, C0, E1
Reading rate: To 10 rdg/s
Software support: National Instruments LabVIEW™ driver (consult Lake Shore for availability)


Electrical format: RS-232C
Baud rates: 9600, 19200, 38400, 57600
Reading rate: To 10 rdg/s
Connector: 9-pin D-sub (DTE)

Output current monitor

Sensitivity: 7 V = 10 A
Accuracy: ±1% of full scale
Noise: 1 mV RMS
Source impedence: 20 Ω
Connector: Shared 15-pin D-sub

Output voltage monitor

Sensitivity: 3.5 V = 35 V
Accuracy: 1% of full scale
Noise: 1 mV RMS
Source impedence: 20 Ω
Connector: Shared 15-pin D-sub

Power supply cooling water

Remote enable input: TTL low or contact closure to enable output; jumper required if unused
Valve power output: 24 VAC at 1 A maximum, automatic or manual control
Connector: Shared 4-pin detachable terminal block
Flow switch and water valve optional

Magnet cooling water

Remote enable input: TTL low or contact closure to enable output; jumper required if unused
Valve power output: 24 VAC at 1 A maximum, automatic or manual control
Connector: Shared 4-pin detachable terminal block
Flow switch and water valve optional


Emergency stop: Requires 1 A, 24 VAC normally closed contact closure to enable power-up; jumper required if unused
Fault output: Relay with normally open or normally closed contact, 30 VDC at 1 A
Remote enable input: TTL low or contact closure to enable output; jumper required if unused
Connector: Shared 8-pin detachable terminal block
Emergency stop and inhibit switches not included


Input power

Power: 5500 VA max
Voltage & current: 204/208 VAC ±10%, 13 A/phase; 220/230 VAC ±10%, 12 A/phase; 380 VAC ±10%, 7 A/phase; 400/415 VAC ±10%, 6.5 A/phase
Protection: 3-phase thermal relay with adjustable current setting; two class CC ¼ A fuses; over-voltage lockout circuit
Frequency: 50 or 60 Hz
Configuration: 3-phase delta
Connector: 4-pin terminal block
Line voltage must be specified at time of order but is field reconfigurable; cable from power supply to facility power not included

Cooling water

Flow rate: 5.7 L (1.5 gal) per min minimum
Pressure range: 34 kPa (5 PSI) to 552 kPa (80 PSI)
Pressure drop: 10 kPa (1.5 PSI) at 5.7 L (1.5 gal) per min minimum for power supply only
Temperature: 15 °C to 30 °C (non condensing)
Connection: Two 10 mm (0.375 in) hose barbs
CAUTION: Internal condensation can cause damage to the power supply

Enclosure type: 7 U high, 19 in rack mount with integral rack mount ears, 25 mm (1 in) air space required on each side for ventilation
Size: 48.3 cm W × 31.0 cm H × 57.2 cm D (19 in × 12.2 in × 22.5 in) with handles removed
Weight: 74 kg (163 lb)
Shipping size: 63.5 cm W × 55.9 cm H × 73.7 cm D (25 in × 22 in × 29 in)
Shipping weight: 80 kg (175 lb)
Ambient temperature: 15 °C to 35 °C at rated accuracy, 5 °C to 40 °C at reduced accuracy
Humidity: 80% to 31 °C decreasing linearly to 50% at 40 °C, (non condensing)
Warm-up: 30 min at output current setting
Approvals: CE mark–low voltage compliance to EN61010-3, EMC compliance to EN55022-1
Calibration schedule: 1 year


Output architecture

The Model 642 output architecture relies on low noise linear input and output stages. The linear circuitry of the Model 642 permits operation with less electrical noise than switch-mode electromagnet power supplies. The clean field background allows greater resolution and finer detail in results drawn from data taken during high sensitivity experiments. One key benefit of this architecture is CE compliance to the electro-magnetic compatibility (EMC) directive, including the radiated emissions requirement.

The true 4-quadrant output capability of the Model 642 is ideal for sweeping through both positive and negative fields. Tightly integrated analog control of the 4-quadrant output provides smooth current change with very low overshoot. This eliminates the need for external switching or operator intervention to reverse the polarity, significantly simplifying system design. The transition through zero current is smooth and continuous, allowing the user to readily control the magnetic. field as polarity changes. This is achieved without reversal contactors or relays, which would produce un-intended field spikes and other discontinuities. As a result, field hysteresis and other biases are avoided in the experimental data.

Output programming

The Model 642 output current is programmed internally via the keypad or the computer interface, externally by analog programming input, or by the sum of the external and internal settings. For internal programming, the Model 642 incorporates a proprietary 20-bit digital-to-analog converter (DAC) that is monotonic over the entire output range and provides resolution of 0.1 mA. External programming provides unlimited resolution.

The Model 642 generates extremely smooth and continuous ramps with virtually no overshoot. The digitally generated constant current ramp rate is variable between 0.1 mA/s and 99.999 A/s. To ensure smooth ramp rate, the power supply updates the high-resolution DAC 23.7 times per second. A low-pass filter on the output DAC smooths the transitions at step changes during ramping.

Output reading

The Model 642 provides high-resolution output readings. The output current reading reflects the actual current in the magnet, and has a resolution of 0.1 mA. The output voltage reading reports the voltage at the output terminals with a resolution of 100 µV. All output readings can be prominently displayed on the front panel and read over the computer interface.



The Model 642 provides built-in protection against short circuit, open circuit, line loss, low line voltage, high line voltage, output over voltage, output over current, over temperature, and abrupt change of the external programming input. In the event of water flow failure, flow sensors provide feedback to the Model 642 and output current is set to 0 A. Internal heat sink, cold plate, and transformer temperatures are also monitored. Warnings are displayed before temperature limits are exceeded and current is set to 0 A. If temperatures continue to increase over safety limits, the Model 642 turns off.

A proprietary circuit limits the power dissipated in the water-cooled cold plate should low resistance and high line conditions exist. The Model 642 protects itself if operated into resistances outside of nominal limits. By limiting current output, the power supply will safely operate into a shorted load, and it operates safely into high resistance loads by limiting voltage output. The Model 642 is also protected against power loss under full operation and nominal magnet load. Both low and high power line conditions are reported on the front panel display.


The Model 642 includes both parallel IEEE-488 and serial RS-232C computer interfaces that provide access to operating data, stored parameters, and remote control of all front panel operating functions. The Model 642 also provides two analog monitors for output current and voltage. Each monitor is a buffered, differential, analog voltage representation of the signal being monitored. The current monitor has a sensitivity of 7 V = 70 A output, while the voltage monitor has a sensitivity of 3.5 V = 35 V output.

Display and keypad

The Model 642 incorporates a large 8-line by 40-character vacuum fluorescent display. Output current and output voltage readings are displayed simultaneously. Five front panel LEDs provide quick verification of instrument status, including ramping, compliance, fault, power limit, and computer interface mode. Error conditions are indicated on the main display along with an audible beeper. Extended error descriptions are available under the status key.

The keypad is arranged logically to separate the different functions of the power supply. The most common functions of the power supply are accessed using a single button press. The keypad can be locked in order to secure either all changes or just the instrument setup parameters allowing the supply output to be changed.