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2.5
SENSOR AND INTERFACE CONNECTIONS
2.5.1
J1 Sensor Input Connections
The Model 818 has one rear panel 5-pin sensor input connector
designated J1 INPUT 1. The Model 819 has four rear panel 5-pin sensor
input connectors designated J1-1, J1-2, J1-3 and J1-4 for inputs 1 thru 4.
Table 2-1 lists sensor lead connection definitions and Figure 2-1
illustrates them.
Use four wire connection (Figure 2-1A) to avoid IR drops in the voltage
sensing pair resulting in temperature measurement error. Use two wire
connection (Figure 2-1B) in less critical applications where lead
resistance is small, and small readout errors can be tolerated.
Lake Shore QUAD-LEAD™ 36 Gauge Cryogenic wire is ideal for sensor
connections since the four color-coded leads run together. The wire is
Phosphor Bronze with a Formvar insulation and
Butryral bonding between the four leads. Color coding
is red, green, clear and blue for easy wire
identification.
2.5.2
J2 Serial I/O
The RS-232C Serial Interface connector is a rear panel mounted RJ-11
modular socket. The connector pins are numbered 1 thru 6 from left to
right. Table 2-2 lists connector pin assignments.
NOTE: When converting from the RJ-11 to DB-25 connector, pins 5, 6, 8
and 20 of the DB-25 connector may need to be shorted together for
proper interface operation.
2.5.3
J3 Alarms
The HI and LO alarm contacts are present on rear panel card edge connections. The Model 818 has one
6-contact card edge connector for the HI and LO alarms. The Model 819 has one 6-contact card edge for
Input 1 HI and LO alarms and one 18-contact card edge connector for Input 2 thru Input 4 HI and LO alarms.
The top and bottom contacts of the card edge are identical in definition and the mating connector supplied
shorts them together. The SPDT alarm contacts are in groups of three: 1 - COM - 2 or NO - lH - NC
representing the contacts for the Input 1 HI alarm. 1 or NO represents the (N)ormally (O)pen state; 2 or NC
represents the (N)ormally (C)losed state. The card edge is slotted between pins 2 and 3 to allow for mating
connector keying. Chapter 3 details alarm action.
2.5.4
J4 Monitors
With an Model 818-MN or 818-LA Option, the J4 Monitors connector is
present. Table 2-3 lists connector pin assignments.
2-2
Lake Shore Model 818 / 819 Cryopump Monitor User's Manual
Table 2-1. Sensor Connections
for the J1 INPUTS
Terminal
A
B
D
E
H
Figure 2-1. Sensor Connections
Table 2-2. Serial I/O Connections
Pin #
1 and 2
3 and 4
5 and 6
Table 2-3. J4 Monitors
Connections
Terminal
A
B
D
E
H
Description
+ Current Out
- Current Out
- Voltage Sense
+ Voltage Sense
Shield
Description
Received Data
Signal Ground
Transmitted Data
Description
V+ MN Output
V- MN Output
V+ LA Output
V- LA Output
Shield
Installation
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