®
2510 TEC SourceMeter
2510-AT Autotuning TEC SourceMeter
The Models 2510 and 2510-AT TEC SourceMeter
instruments enhance Keithley’s CW (Continuous
Wave) test solution for high-speed LIV (light-current-voltage) testing of laser diode modules.
These 50W bipolar instruments were developed
in close cooperation with leading manufacturers
of laser diode modules for fiberoptic telecommunications networks. Designed to ensure tight
temperature control for the device under test,
the Model 2510 was the first in a line of highly
specialized instruments created for telecommunications laser diode testing. It brings together
Keithley’s expertise in high-speed DC sourcing
and measurement with the ability to control the
operation of a laser diode module’s ThermoElectric Cooler or TEC (sometimes called a
Peltier device) accurately.
The Model 2510-AT expands the capability of the
Model 2510 by offering autotuning capability. P,
Thermistor Peltier
GPIB
Ordering Information
2510 TEC SourceMeter
2510-AT Autotuning TEC
Extended warranty, service, and
calibration contracts are available
Accessories Supplied
User’s Manual, Input/Output
Connector
ACCESSORIES AVAILABLE
2510-RH Resistive Heater Adapter for Model 2510
2510-CAB 4-Wire Unshielded Cable, Phoenix Connector to
APPLICATIONS
Control and production testing of
thermoelectric coolers (Peltier
devices) in:
• Laser diode modules
• IR charge-coupled device (CCD)
arrays and charge-injection
devices (CID)
• Cooled photodetectors
• Thermal-optic switches
• Temperature controlled fixtures
SourceMeter
.
Unterminated End
I, and D (proportional, integral, and derivative) values for closed loop temperature control are determined by the instrument using a modified Zeigler-Nichols algorithm. This eliminates the need for
users to determine the optimal values for these coefficients experimentally. In all other respects, the
Model 2510 and Model 2510-AT provide exactly the same set of features and capabilities.
The SourceMeter Concept
The Model 2510 and Model 2510-AT draw upon Keithley’s unique SourceMeter concept, which combines precision voltage/current sourcing and measurement functions into a single instrument.
SourceMeter instruments provide numerous advantages over the use of separate instruments, including lower acquisition and maintenance costs, the need for less rack space, easier system integration
and programming, and a broad dynamic range.
Part of a Comprehensive LIV Test System
In a laser diode CW test stand, the Model 2510 or Model 2510-AT can control the temperature of
actively cooled optical components and assemblies (such as laser diode modules) to within ±0.005°C
of the user-defined setpoint. During testing, the instrument measures the internal temperature of the
laser diode module from any of a variety of temperature sensors, then drives power through the TEC
within the laser diode module in order to maintain its temperature at the desired setpoint. Active
Figure 1. The capabilities of
the Models 2510 and 2510AT are intended to complement those of other Keithley
instruments often used in
laser diode module LIV testing, including the Model
2400 and 2420 SourceMeter
instruments, the Model 2502
Dual Photodiode Meter, and
the Model 2500INT
Integrating Sphere.
2400/
2420
Computer
2510 or
2510-AT
Fiber
®
Precision temperature control for TECs with auto tuning PID for optimal performance
Trigger Link
2502
2500INT
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www.keithley.com
OPTOELECTRONICS TEST
A GREATER MEASURE OF CONFIDENCE
281
2510 TEC SourceMeter
2510-AT Autotuning TEC SourceMeter
• 50W TEC Controller combined
with DC measurement functions
• Fully digital P-I-D control
• Autotuning capability for the
thermal control loop (2510-AT)
• Designed to control temperature
during laser diode module testing
• Wide temperature setpoint range
(–50°C to +225°C) and high
setpoint resolution (±0.001°C)
and stability (±0.005°C)
• Compatible with a variety of
temperature sensor inputs—
thermistors, RTDs, and IC sensors
• Maintains constant temperature,
current, voltage, and sensor
resistance
• AC Ohms measurement function
verifies integrity of TEC
• Measures and displays TEC
parameters during the control
cycle
• 4-wire open/short lead detection
for thermal feedback element
• IEEE-488 and RS-232 interfaces
• Compact, half-rack design
Precision temperature control for TECs with auto tuning PID for optimal performance
Tem p
T
MAX
Max.
Initial
Slope
T
START
Figure 2.
Temp (°C)
Figure 3.
Temp (°C)
Figure 4.
L
Laser Diode TEC Minimum Overshoot
27
26
25
24
23
0 5 10 15 20 25
Laser Diode TEC Minimum Settling Time
27
26
25
24
23
0 5 10 15 20 25
t
L
T
S
Time (s)
Time (s)
t
63%
e
temperature control is very
important due to the sensitivity of
laser diodes to temperature
changes. If the temperature
varies, the laser diode’s dominant
output wavelength may change,
leading to signal overlap and
crosstalk problems.
Autotuning Function
Time
The Model 2510-AT Autotuning
TEC SourceMeter instrument
offers manufacturers the ability to
automatically tune the temperature control loop
required for CW testing of optoelectronic components such as laser diode modules and thermo-optic switches. This capability eliminates the
need for time-consuming experimentation to
determine the optimal P-I-D coefficient values.
The Model 2510-AT’s P-I-D Auto-Tune software
employs a modified Ziegler-Nichols algorithm to
determine the coefficients used to control the PI-D loop. This algorithm ensures that the final
settling perturbations are damped by 25% each
cycle of the oscillation. The autotuning process
begins with applying a voltage step input to the
system being tuned (in open loop mode) and
measuring several parameters of the system’s
response to this voltage step function. The system’s response to the step function is illustrated
in Figure 2. The lag time of the system
response, the maximum initial slope, and the
TAU [63% (1/e)] response time are measured,
then used to generate the Kp (proportional gain
constant), Ki (integral gain constant), and Kd
(derivative gain constant) coefficients.
The autotuning function offers users a choice of
a minimum settling time mode or a minimum
overshoot mode, which provides the Model
2510-AT with the flexibility to be used with a
variety of load types and devices. For example,
when controlling a large area TEC in a test fixture optimized for P, I, and D values, minimum
overshoot protects the devices in the fixture
from damage (Figure 3). For temperature setpoints that do not approach the maximum specified temperature for the device under test, the
minimum settling time mode can be used to
speed up the autotuning function (Figure 4).
50W Output
As the complexity of today’s laser diode modules
increases, higher power levels are needed in
temperature controllers to address the module’s
cooling needs during production test. The 50W
(5A @ 10V) output allows for higher testing
282
1.888.KEITHLEY (U.S. only)
OPTOELECTRONICS TEST
www.keithley.com
A GREATER MEASURE OF CONFIDENCE
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