Lake Shore Model 642 Electromagnet Power Supply User’s Manual
Introduction
1-3
Description (Continued)
Interfaces
The Model 642 includes IEEE-488 and RS-232C interfaces that provide access to operating data, stored parameters, and
remote control of all front panel operated functions. A keypad lock-out feature is provided to prohibit any changes made
from the front panel. The Model 642 can then be operated solely with the computer via the RS-232C or IEEE-488
interface.
The Model 642 provides two analog outputs to monitor the output current and voltage. Each output is a buffered,
differential, analog voltage representation of the signal being monitored. The current monitor has a sensitivity of
7 V = 70 A, while the voltage monitor has a sensitivity of 3.5 V = 35 V.
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 LEDs on the front panel provide quick verification of instrument
status, including ramping, power limit, compliance, fault, and computer interface mode. Error conditions are indicated on
the main display along with an audible tone. Extended error descriptions are available in an error message screen by
pressing the Status key.
The keypad is arranged logically to separate the different functions of the instrument. The most common functions of the
power supply are accessed using a single key press. The keypad can be locked to either lock out all changes or to lock
out just the instrument setup parameters allowing the output of the power supply to be changed.
1.2 SPECIFICATIONS
Output
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
Nominal load
0.5
Ω
, 0.5 H
Maximum load resistance
0.6
Ω
for
±
70 A DC operation at +10% to –5% line voltage
Minimum load resistance
0.4
Ω
for
±
70 A at +5% to –10% line voltage
Load inductance range
0 H to 1 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 maximum into a resistive load
Compliance voltage (AC)
±43 V at +10% to –5% line
Settling 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
