Lakeshore Learning Materials 647 User Manual

Page 20

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Lake Shore Model 647 Magnet Power Supply User’s Manual

Setup & Connections

2-4

2.5.2 Shielding, Grounding, and Noise
For noise reduction, tightly twist and shield the leads from the MPS to the magnet. Connect the shield to the

MPS chassis as shown in figure 2-4.

WARNING:

DO NOT place magnet leads in contact with other MPS/system connections or metal parts.

In some instances, the user's measurement leads may pick up noise from the magnet leads. Although this

common mode noise may affect the user's measurement it rarely affects the current in the magnet. If the

user's measurement is earth grounded, some improvement is almost always possible by tying the –OUT

terminal of the MPS to earth ground – either at the MPS chassis or, if the user's system has one, the common

system earth ground point.

WARNING: If the – OUT terminal is tied to earth ground, make certain the +OUT cable from the MPS

contacts no other earth ground point - it forces the MPS output current into this other ground point. If

the other ground point is a small wire, it may melt or catch fire.

2.5.3 MPS Remote Inhibit and Fault Indicator Connections
The MPS has a Fault Indicator

(FLT) output and a discrete

Remote Inhibit (RI) input which

are both interface independent

and provide fault indication and

remote output shutdown in the

event of catastrophic failure. The

Fault Indicator relay contact is

open when the MPS detects no

faults. When the MPS detects an

internal fault, a remote inhibit, or

an output inhibit, it lights the front

panel Fault LED and closes the

relay contact. The contact closure

alerts other system components

of the fault. In an auto-parallel

system (up to four MPS units

connected in parallel) these

signals connect in parallel

between each of the MPS units

(See Paragraph 2.6 for details on

connections between two auto-

parallel units). Make connections

to a rear panel detachable

terminal block defined in Table 2-

3 and Figure 2-2.


2.5.4 AC On Indicator
The MPS provides a discrete ON indicator. Terminals 5 and 6 on the terminal block connector, shown in

Figure 2-2 above, connect to relay contacts that close when the front panel circuit breaker is in the ON

position. There is also a front panel LED that lights when the MPS is ON and connected to AC power.

2.5.5 OVP

Connection

In auto-parallel MPS configurations, this connection synchronizes the firing of the Over Voltage Protection

(OVP) circuits of each MPS (see Chapter 5). See Paragraph 2.6 and Figure 2-5 for auto-parallel connections.

TERMINAL LABEL

DEFINITION

1
2

RI+
RI–

Remote Inhibit – Active low, TTL-compatible input to
remotely force the output settings to 0 A and 1 V. Also
activate RI by shorting +RI to -RI with a relay contact closure
or a switch.

3
4

FLT+
FLT–

Fault Indicator – A relay contact that closes to indicate a
fault. Contact rating: 0.25 A resistive at 100 VDC, 3 W, 25
VA.

5
6

ON+
ON–

ON Indicator – A relay contact that closes to indicate when
the front panel circuit breaker is in the ON position. Contact
rating: 0.25 A resistive at 100 VDC, 3 W, 25 VA.

7

NONE

Factory Use Only. Do not connect to this terminal.

8

OVP

In auto-parallel MPS configurations, OVP ensures that the
activation of one MPS Over Voltage Protection circuit
activates all the other parallel MPS units' protection circuits.

Table 2-3

RI, FLT, ON, and OVP Connections

Figure 2-2

RI, FLT, ON and OVP Connections

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