Temperature Measurement Setup; Table 3.2 Display Indicators - ILX Lightwave LDX-36000 Series User Manual

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C H A P T E R

Table 3.2 Display Indicators

Condition
Current Limit
Voltage Limit
Open Circuit
Const %
Const Freq
Interlock 1
Interlock 2
Temp Sensor Open
Temp Limit

Temperature Measurement Setup

The LDX-36000 Series High Power Laser Current Sources are designed to
measure temperature of a laser diode mount and disable the output if temperature
exceeds a specified value. Temperature measurement is accomplished by
measuring the resistance of a negative temperature coefficient (NTC) thermistor.
An NTC thermistor is a device whose resistance decreases with increasing
temperature in a highly nonlinear fashion. A current of 100 µA is used to enable
measurement of the voltage across the thermistor. By measuring the voltage and
knowing the current flowing through the thermistor, the resistance may be
calculated by Ohm's Law.
The resistance of an NTC thermistor is a nonlinear function of temperature
characterized by the Steinhart-Hart Equation. This equation is described in detail
in several ILX Lightwave Application and Tech Notes available from the ILX
website and may be referred to for additional information. In the LDX-36000,
three constants are required to calculate the temperature from the measured
resistance and are specified as the thermistor calibration constants C1, C2 and
C3. These constants will change depending on the thermistor used, in terms of
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 LDX-36000 Series
O P E R A T I O N
Front Panel Operation
Action
Current Limit LED flashes at 1 Hz.
Voltage Limit LED flashes at 1 Hz. If the limit is reached, the output will be
disabled.
Output off; Open Circuit LED flashes at 1 Hz. If this condition was caused by
excessively high compliance voltage, the Voltage Limit LED will be illuminated
as well.
Duty cycle percentage remains constant when pulsewidth is changed, resulting
in a change in output frequency.
Illuminated when either left-hand P
Output pulse frequency remains constant when pulsewidth is changed,
resulting in a change in duty cycle.
Illuminated when either right-hand P
Output off; Interlock 1 LED flashes at 1 Hz.
Output off; Interlock 2 LED flashes at 1 Hz.
Output off; Temp Sensor Open LED illuminated. Output off action may be
disabled via the Output Off Register or setting thermistor calibration constants
to zero.
Output off; Temp Limit LED illuminated. Output off action may be disabled via
the Output Off Register or setting thermistor calibration constants to zero.
or % button is pressed.
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or Freq button is pressed.
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