Meter Calibrations

General Requirements

Instruments used to detect radiation must be calibrated annually. This includes both handheld survey meters and benchtop equipment. EHS no longer provides calibration services, and the PI is responsible for coordinating calibration of their equipment in a timely manner. Loaner meters are available upon request, but supplies are limited. Calibrations should be planned with this in mind. 

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Send handheld meters back to manufacturer for calibration

Since EHS no longer provides calibration services as of October 1, 2022, the PI is responsible for shipping meters back to the manufacturer for calibration. Most meters on campus are manufactured by Ludlum and can be sent to the Ludlum Service Department for calibration. To ship meters back to Ludlum for calibration:

  1. Ludlum typically calibrates meters within four weeks, so begin this process early enough to ensure that calibrated detection equipment is still available for use in the lab.
  2. Fill out the Instrument Return Form found under the Rad Forms link to the right.
  3. Include the serial number of both the meter body as well as the detector probe.
  4. Indicate on the form if Ludlum needs to evaluate the meter for repairs as well. EHS recommends including a comment such as "calibrate and repair if necessary."
  5. If you need additional calibrations for your research, be sure to include this in the comments section. For example, if you need your meter to be calibrated for Lu-177, you could write something such as "include calibration for Lu-177" in the comments section. Note that each additional radionuclide listed may add additional charges.
  6. Do not include your check source in the shipping container. Some check sources have high enough activities that they require Department of Transportation (DOT) training to properly label and mark the container.
  7. Package the meter in an appropriate shipping container. The shipping address can be found on the Ludlum Instrument Return Form. For reference, the shipping address is:
    • ATTN: Service Dept.
    • 501 Oak St.
    • Sweetwater, TX 79556
  8. When you receive your calibrated meter back, send a copy of the calibration certificate to and save a copy for your records as these may be reviewed during HP audits.
  9. Ludlum will send the meter back in a Ludlum specific shipping container that has foam fitted to your meter. EHS recommends keeping this box to use for future calibrations. 

If you have any questions on shipping your meters back, contact MU EHS Radiation Safety at If you are shipping back a pressurized ion chamber such as a Ludlum 9DP, review the information on depressurizing your ion chamber prior to shipping. 


Depressurize your ion chamber

If you are sending an ion chamber for calibration, you will need to depressurize the meter prior to shipping. If a meter is not depressurized, DOT training and additional shipping requirements may be necessary. Most pressurized ion chambers at MU are Ludlum 9DPs. If you have one of these meters, watch the Ludlum video How To Decompress the Model 9DP. If you need additional assistance, or if you have a meter that you believe is pressurized that is not a Ludlum 9DP, contact


Schedule benchtop equipment calibrations

PIs can schedule benchtop equipment calibrations by contacting the vendor, manufacturer, or a maintenance group. For newer equipment, the manufacturer should still be available to provide calibration and maintenance services. If you need an outside group (most likely for older equipment that is no longer supported by the manufacturer), Specialty Underwriters (SU) may be available to coordinate annual calibrations. Contact information for SU is:

  • Alec Christensen, Market Specialist
  • SU Group LLC
  • P: (800) 558-9910, Ext. 2909
  • C: (262) 664-9323


Calibrate your LSC

The RSS recommends getting LSC standards for your LSC calibration. The standard set by LSC manufacturers typically includes C-14, H-3, and a background standard. You can find more detailed information in the "Instrument Calibrations" SOP by clicking the Radiation Safety SOPs link to the right. On that page, you can also find an excel template for calculating efficiencies using your LSC standards.


Page last updated on February 2, 2024.