Lakeshore Learning Materials 642 - Manual (Page 39)

Lake Shore Model 642 Electromagnet Power Supply User’s Manual
Installation 3-11
3.9 ANALOG INPUT/OUTPUT CONNECTIONS
The Analog I/O connector provides connections to analog signals used to monitor or control the power supply. A Current
Program input is provided to control the current output. Two outputs are also provided to monitor the output current and
the output voltage. The connector and pin-out table is shown in figure 3-15. Specific information on each function is
provided in paragraphs 3.9.1 and 3.9.2.
1
8 15
9
Pin Name Pin Name
1
2
3
4
5
6
7
8 NC
Chassis
Current Program –
Chassis
Voltage Monitor –
Chassis
Current Monitor –
Chassis
9
10
11
12
13
14
15
NC
Chassis
Current Program +
Chassis
Voltage Monitor +
Chassis
Current Monitor +
Figure 3-15. Model 642 Analog Input/Output Connector
3.9.1 External Current Programming
The output current can be programmed externally using an AC or DC voltage. This programming voltage can also be
summed with the internal current setting or ramp. Refer to Paragraph 4.15 to change the external current program mode.
The external current programming input is a differential input with a sensitivity of 10 V = 70 A and an input impedance
of > 50 k
Ω . The programming voltage is limited internally to approximately ±10.1 V (Category 1) but care must be taken
to insure that maximum current capability of the magnet is never exceeded.
3.9.2 Output Current and Voltage Monitors
The output current and output voltage of the power supply can be monitored externally using the monitor output
connections on the Analog I/O connector. 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 and the voltage monitor has a sensitivity of
3.5 V = 35V. Both outputs have a source impedance of 20 Ω.
3.10 COMPUTER INTERFACE
The Model 642 can be programmed externally with a computer. Both RS-232C and IEEE-488 ports are provided.
3.10.1 RS-232C Interface Connection
An RS-232C port has been provided to allow remote computer control of the power supply. (Refer to Chapter 5,
Computer Interface Operation)
3.10.2 IEEE-488 Interface Connection
An IEEE-488 port has been provided to allow remote computer control of the power supply. (Refer to Chapter 5,
Computer Interface Operation)
3.11 CHASSIS CONNECTION
A 6-32 screw has been provided for attaching an optional chassis ground connection. This connection is normally not
required. However, occasionally there are noise problems associated with a floating magnet or other ancillary equipment.