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2
C H A P T E R
Output Connectors
The TE drive current is available at the 15-pin D-connector (J301). Pins 1 and 2
are jumpered for the positive output, and pins 3 and 4 are jumpered for the
negative output to the TE module. The thermistor connects to pins 7 and 8.
If an external resistor is to be used for the SET RESISTANCE, it must be
connected across pins 5 and 6. The SET RESISTANCE switch must be in the
EXT position in order to activate that mode of operation.
The Control Signal is available at pin 10 of J301. This provides (approximately) a
1 V/A signal which can be used to drive booster current supplies.
Grounding Considerations
The outputs of the LDT-5412 are isolated from chassis ground, allowing either
output terminal to be grounded at the user's option.
THERMISTOR CURRENT Switch
The thermistor source current set switch selects the thermistor current supply of
either 10 uA or 100 uA. Selecting the supply current depends on the thermistor
operating temperature range and the required temperature resolution. Guidelines
for setting this switch are contained in Chapter 6.
SET RESISTANCE Switch
The SET RESISTANCE switch allows the user to bypass the set resistance
function of the front panel and externally connect a known resistor for temperature
control.
When the switch is in the EXT position, and a resistor is connected between pins
5 and 6 of J301, the 5412 uses the external resistance as its reference set point
and adjusts the output accordingly. In this mode, the front panel set resistance is
ignored; if the external resistor becomes disconnected (open circuit), the OPEN
THERM fault indicator will come on (in addition to it coming on if the thermistor is
open). This mode is useful if operation at one specific temperature is normally
required. A wire-wound resistor is recommended for greatest temperature
stability.
When the switch is in the INT position, the external resistor is disconnected, the
front panel controls the set resistance, and the OPEN THERM fault indicator will
only light when the thermistor connection is an open circuit.
8
LDT-5412
O P E R A T I O N
Rear Panel
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