If your spectrometer isn’t calibrating or is showing unusually noisy or high absorbance values (often above 3 or blank), the issue may be due to insufficient light reaching the detector. This happens when:

• The light source is weak in a certain spectral region, or
• Almost no light reaches the detector.

In these cases, the difference between the light and dark signal may be too small to produce reliable readings. There are a few possible causes. Review the tips below to identify and resolve the issue.

CHECK THE SAMPLE CONCENTRATION
For best results, absorbance values should fall between 0.1 and 1.0 absorbance units across all relevant wavelengths.

• If your samples are too concentrated, you may see empty cells or absorbance values stuck at 3.0, indicating too much noise.
• In this case, dilute your samples and test again.
• 📘 For example, in the Advanced Chemistry with Vernier Copper Sulfate experiment, use 0.1 M Copper Sulfate as your most concentrated solution—not 0.4 M, which was designed for a colorimeter.
  →See Why is the absorbance reading on my device (spectrometer/colorimeter) unstable or nonlinear at values above 1.0? for more

CHECK THE SPECTROMETER’S LIGHT SOURCE
If the internal light source is weak or burned out, the detector may not receive enough light to generate reliable data.

• Switch to Uncalibrated Mode and observe the full spectrum.
• If the graph is flat in certain regions, this may indicate a faulty or degraded light source.
  → See How do I check the lamp output of my spectrometer? for detailed instructions

VERIFY THE LIGHT PATH IS CLEAR
Make sure the cuvette is:

• Inserted correctly (aligned with the arrow or frosted sides out, if applicable)
• Filled with enough sample to reach the light path
• Using the correct solvent and compatible cuvette material for your spectrometer type (e.g., quartz for UV measurements).
  → For more information, see What is the difference between the types of cuvettes you sell for Spectrometers and the Colorimeter?
• After making adjustments, recalibrate the spectrometer before collecting data again.

LABQUEST 2 OR 3 USERS – Check for Power Issues
Some connection and calibration problems may stem from power-related issues when using a SpectroVis Plus or Go Direct SpectroVis Plus with a LabQuest 2 or 3.
→ See LabQuest Not Recognizing SpectroVis Plus or Showing Bad Data for troubleshooting tips
→ See Full Power Reset Instructions in My Go Direct SpectroVis Plus is not identified or won't turn on.

UV-VIS SPECTROMETER-SPECIFIC TIPS
(Applies to Go Direct UV-VIS, Go Direct UV-VIS/Fluorescence, etc.)

• Use the correct cuvettes.
  Standard plastic cuvettes block UV light and cause poor readings. Use UV-VIS compatible plastic or preferably quartz cuvettes for best results. Even some UV-compatible plastics may introduce noise.
  → See What is the difference between the types of cuvettes you sell for Spectrometers and the Colorimeter? for cuvette guidance
• Check your solvent.
  Solvents that absorb strongly in the UV (like concentrated nitric acid) can prevent light from reaching the detector.
  • Try taking a blank with water and then measure your solvent directly.
  • If absorbance is high, consider diluting or switching solvents.
• You may also be interested in What are some tips for improving my Fluorescence/UV-VIS Spectrophotometer data?

CHECK THE SERIAL NUMBER
Check that the serial number displayed in software matches the label on your spectrometer.
If there’s a mismatch, the device may not be properly recognized or configured.
→ See Spectrometer Error: 'Could Not Collect Values' or 'Calibration Failed' to locate the serial number in your software

If these steps don’t solve the issue—or if the problem happens repeatedly with the same spectrometer—please contact Vernier Technical Support (chemistry@vernier.com. When you reach out, be sure to include:
– The serial number of your spectrometer
– The software (Spectral Analysis or LabQuest) and connection type (USB or BLE) you are using
– A summary of the troubleshooting steps you’ve already tried

Related TILs
LabQuest Not Recognizing SpectroVis Plus or Showing Bad Data
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My Spectrometer is not working properly. It won't calibrate or is giving very noisy data.
Spectrometer Error: 'Could Not Collect Values' or 'Calibration Failed'