O P E R A T I O N S
Functions and Features
34
LDC-3700 Series
C H A P T E R
2
This condition is indicated by the
OUTPUT
SHORTED
indicator becoming lit. To disable the output,
press the
OUTPUT
push button again.
Boosting the TE Controller
For users who need more than 16 Watts of TE Controller power, a booster current source may be
required and the LDC−3700B Series Temperature Controller may be used as the control element.
This section describes the use of the LDC−3700B’s Temperature Controller as a remote temperature
controller.
Whenever a connection is present between the
BOOSTER
PRESENT
(pin 14) and
DIGITAL
GROUND
(pin 15) of the back panel TEC Input/Output connector (see Figure 2.5), the LDC−3700B’s
TEC OUTPUT will be disabled. In this case, a BOOST CONTROL signal voltage equal to +10.0
volts will be available for controlling an independent current source. This control voltage is available
between the
BOOST
CONTROL
(pin 10) and
AGND
(pin 9).
Figure 2.5
Rear Panel TEC Connector
All functions of the temperature controller can be utilized as in normal TEC operation with the
exception of the TE Current Limit. When the controller is configured in BOOSTER MODE, the LIM I
value may be increased above the normal operating maximum of 4.0 Amps, to a maximum of 10.0
Amps. The control signal voltage, +10 V is linearly proportional to the control current, which is
limited by the
LIM
I
parameter.
Pins 11 and 12 are outputs from the TEC controller hardware. These lines are TTL−level indicators
of the TEC voltage and limit conditions, respectively. They are useful for external sensing of these
conditions in addition to the normal status reporting of the LDC−3700B Series instrument.
Pin 13 is used as an external shutoff switch. Although it is labeled as "Temp. Limit", its function is to
shut off the TEC controller. This function is controlled by applying a TTL−level signal to pin 13. When
this input is high, the LDC−3700 Series instrument will shut the TEC controller off.
The feedback loop
GAIN
will require adjustment when a booster current source is used. The higher
thermal loads will require larger or smaller
GAIN
values in order to settle to the set temperatures in a
desirable fashion. See "Setting TE Control Loop Gain" in Chapter 2.
ON
OUTPUT
I
HBW
P
I
SELECT
LASER MODE
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
1, 2 TE Module (+)
3, 4 TE Module (-)
5 TE Module Shield
6 Sensor Shield
7 Sensor (+)
8 Sensor (-)
9 Analog Ground
10 Control Signal
11 Voltage Limit
12 Current Limit
13 Temp. Limit
14 Booster Present
15 Digital Ground
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