Setting Temperature with NTCAFLEX05103HH

Overview

This section describes how to set the temperature control parameters when using the recommended NTCAFLEX05103HH 10kΩ foil NTC sensor with the TEC controller.

Important Distinction

Disconnect NTC During Setup

Disconnect the NTC from the driver before setting the temperature values.

Setting the values with NTC connected will lead to wrong settings.

Setup Procedure

Step-by-Step Instructions

1. Disconnect the NTC from the driver (if connected)

2. Disconnect the power supply from the driver

3. Locate the TEMP potentiometer on the driver board

4. Find the TEMP ADJ measurement points

   • Two holes next to the TEMP potentiometer
   • Used for resistance measurement

5. Select desired temperature from the R/T table below

6. Measure resistance at TEMP ADJ points using a multimeter

7. Adjust TEMP potentiometer until resistance matches R_POT value from table

8. Connect the power supply to the driver

9. After setting, connect the NTC to the driver

R/T Values for TEC Control

Temperature Reference Table

Temperature (°C)	Nominal Temp (°C)	Hysteresis Temp (°C)	Threshold Temp (°C)	RPOT (kΩ)
5	6	11	46.2085
10	13	17	36.1246
15	19	23	28.4575
20	25	29	22.5826
25	31	35	18.0488
30	36	41	14.5235
35	42	46	11.7635
40	47	51	9.5884
45	52	56	7.8631
50	57	61	6.4860
55	62	66	5.3803
60	67	71	4.4873
65	71	76	3.7619
70	76	80	3.1697
75	80	84	2.6837
80	84	88	2.2826
85	88	93	1.9504
90	92	96	1.6735
95	96	100	1.4420
100	100	104	1.2475

Understanding the Table Columns

Temperature

The target operating temperature you want to maintain with the TEC controller.

Nominal Temperature

The actual setpoint that the TEC will regulate to. This is the temperature at which the TEC will maintain the laser diode.

Hysteresis Temperature

The temperature at which the laser can be re-enabled after a thermal shutdown. The laser must cool below this value before recovery.

Threshold Temperature

The safety shutdown temperature. If the temperature exceeds this value, the laser will be disabled immediately to prevent damage.

R_POT

The resistance value (in kΩ) you need to set at the TEMP ADJ measurement points.

Temperature Relationships

Example: 25°C Setting

Set Temperature:        25°C
                         ↓
R_POT Setting:      18.0488 kΩ
                         ↓
                    ┌────────┐
Nominal (TEC Target): 25°C   │ TEC regulates here
                         ↓    │
Temperature Rising       ↓    │
                         ↓    │
Hysteresis:         31°C ─────┤ Can re-enable after shutdown
                         ↓    │
Still Rising             ↓    │
                         ↓    │
Threshold (Shutdown): 35°C ───┘ Safety shutdown trigger

Temperature Zones

  15°C ═══════════════════════════════
        Cold - TEC Off
  ↓
  25°C ─────────────────────────────── Nominal (TEC Target)
        TEC Active Zone
  ↓
  31°C ─────────────────────────────── Hysteresis (Re-enable Point)
        Safety Margin
  ↓
  35°C ─────────────────────────────── Threshold (Shutdown)
        Overtemperature Zone
  ↓
  50°C ═══════════════════════════════

NTC Sensor Specifications

Sensor-Specific Values

The resistor values shown in the table are only valid for the included 10k foil NTC (NTCAFLEX05103HH).

If you want to use a different 10k NTC, the values need to be adapted. Please follow the instructions in the next chapter “Setting Temperature with Other NTCs”.

NTCAFLEX05103HH Characteristics

Parameter	Value
Nominal Resistance	10 kΩ @ 25°C
Beta Value (B25/85)	3960 K
Tolerance	±1%
Type	Foil NTC
Form Factor	Small, flexible

Setting Procedure Details

Measurement Technique

1. Set multimeter to resistance (Ω) mode
2. Select range: 20 kΩ or 200 kΩ
3. Place probes on TEMP ADJ measurement points
4. Read displayed resistance
5. Adjust potentiometer slowly clockwise/counterclockwise
6. Watch resistance change on multimeter
7. Fine-tune to match table value exactly

Achieving Accurate Settings

Accuracy Tips

• Use a quality digital multimeter (minimum 3½ digits)
• Ensure solid probe contact
• Allow reading to stabilize (2-3 seconds)
• Approach final value slowly
• Double-check before finalizing

Common Temperature Settings

Typical Applications

Application	Target Temp	Nominal	Threshold	RPOT
Room Temperature	25°C	31°C	35°C	18.0488 kΩ
Wavelength Stabilization	25°C	31°C	35°C	18.0488 kΩ
Cooled Operation	20°C	25°C	29°C	22.5826 kΩ
Precision Cooling	15°C	19°C	23°C	28.4575 kΩ
High Power	30°C	36°C	41°C	14.5235 kΩ

Installation Considerations

NTC Placement

Critical Placement Rule

The distance between the laser diode, the NTC, and the TEC needs to be chosen as short as possible.

Otherwise, the driver will not be able to keep the temperature stable and may oscillate.

Optimal NTC Installation

Best practices:

1. Mount NTC directly on laser package
2. Use thermal paste for good contact
3. Secure firmly (avoid movement)
4. Protect from mechanical damage
5. Keep wires short

TEC Element Placement

• TEC in direct thermal contact with laser mount
• Good thermal paste application
• Adequate heat sink on TEC hot side
• Proper insulation from housing

Verification After Setup

Startup Verification

1. Power up the system

2. Check Power LED - ON

3. Check TEMP LED:

   • Should be ON (NTC connected, temp OK)
   • If OFF: Check NTC connection
   • If flashing: Temperature too high

4. Monitor TEC LED:

   • OFF when temp below nominal
   • ON when TEC is cooling

5. Observe temperature stabilization:

   • Should settle at nominal temperature
   • TEC LED ON during active regulation
   • Stable within a few minutes

Functional Testing

Test sequence:

1. Set low nominal temperature (e.g., 20°C)
2. Power up at room temperature (~23°C)
3. Expected: TEC LED turns ON immediately
4. Temperature should drop toward 20°C
5. TEC regulates to maintain 20°C
6. Enable laser
7. TEC compensates for laser heat
8. Temperature remains stable at 20°C

Troubleshooting Setup

TEC Never Activates

Symptoms:

• TEC LED always OFF
• Temperature above nominal

Possible Causes:

• TEC board not installed
• Wrong resistance setting
• TEC polarity reversed

Solutions:

• Verify TEC controller installed
• Re-check R_POT value
• Verify TEC connections

Temperature Oscillates

Symptoms:

• Temperature cycles up and down
• TEC LED flashing on/off
• Unstable operation

Possible Causes:

• NTC too far from laser
• Poor thermal contact
• Excessive thermal lag
• Wrong R_POT value

Solutions:

• Reposition NTC closer
• Improve thermal coupling
• Verify R_POT setting
• Add thermal mass

Cannot Reach Target Temperature

Symptoms:

• Temperature always above nominal
• TEC LED always ON
• Maximum TEC current

Possible Causes:

• Inadequate TEC capacity
• Poor heat sinking
• Ambient too high
• Excessive heat generation

Solutions:

• Verify TEC size adequate
• Improve heat sink
• Reduce ambient temperature
• Reduce laser power

Frequent Threshold Shutdowns

Symptoms:

• TEMP LED frequently flashing
• Laser disabled often
• Cannot maintain temperature

Possible Causes:

• TEC undersized
• Poor thermal design
• Nominal too close to threshold

Solutions:

• Increase TEC capacity
• Improve cooling system
• Lower nominal temperature
• Improve thermal design

Temperature Stability

Achieving Stable Control

Key factors:

1. ✅ Minimal thermal resistance
2. ✅ Short thermal time constants
3. ✅ Adequate TEC capacity
4. ✅ Proper NTC placement
5. ✅ Good heat sinking

Expected Performance

Parameter	Typical Value
Settling Time	1-5 minutes
Temperature Stability	±0.5°C
Long-term Drift	<±1°C

Documentation

Record Your Settings

Document the following:

• Date: Configuration date
• Target Temperature: Desired operating point
• R_POT Value: Resistance set
• NTC Type: NTCAFLEX05103HH
• TEC Specifications: Current, voltage rating
• Verification Results: Actual temperatures achieved
• Notes: Any observations or issues

Maintenance

Keep this documentation for:

• Future troubleshooting
• Reconfiguration needs
• System upgrades
• Warranty support