Calibrating Instruments: A Guide

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In summary, a proper calibration process for a PMT involves measuring its quantum efficiency as a function of wavelength using a weak light source. If the PMT is connected to an NaI detector, calibrations are performed on the SCAs and MCAs, not the probes themselves. This is done by creating a relationship between the voltage knob and the energy of detected photons through the use of a region of interest (ROI), typically with cesium-137 and an ROI of 612keV to 712keV.
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Nomy-the wanderer
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What can be defined as a proper calibration process for such an instrument?
 
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The PMT itself ? Or integrated in an instrument ?

In pulse mode, what would give you the "calibration" of a PMT is the quantum efficiency as a function of wavelength. That can be done by having a weak light source of variable wavelength, and calibrating the count rate against the count rate of a PMT with known quantum efficiency for instance.
 
  • #3
How about a PMT connected to an NaI detector, and a nim with an amplifier and a SCA + counter...
 
  • #4
Calibrations are performed on SCAs and MCAs, not the probes (ie. the NaI probe)themselves. Since this is an SCA, you want to create a relationship between the knob that increases voltage and the energy of the photons being detected. This is done by creating a region of interest (ROI) and finding which setting of the knob creates the highest count rate in that ROI. Typically its performed with cesium-137 and an ROI of 612keV to 712 keV.
 

1. What is the purpose of calibrating instruments?

The purpose of calibrating instruments is to ensure that they are measuring accurately and providing reliable data. This is especially important in scientific research where even small inaccuracies can have significant impacts on results and conclusions.

2. How often should instruments be calibrated?

The frequency of calibration depends on the type of instrument and how often it is used. In general, it is recommended to calibrate instruments at least once a year. However, if the instrument is used frequently or in critical applications, it may need to be calibrated more frequently.

3. Can I calibrate my instruments myself?

In some cases, it may be possible to calibrate instruments yourself, but it is generally recommended to have them calibrated by a professional. Professional calibration labs have specialized equipment and trained technicians who can ensure that the instruments are calibrated accurately and according to industry standards.

4. What is the difference between calibration and adjustment?

Calibration involves comparing the measurements of an instrument to a known standard and making any necessary adjustments to bring it into alignment. Adjustment, on the other hand, involves physically changing the instrument's internal components to improve its accuracy. Calibration is typically a simpler and less invasive process.

5. Are there any risks associated with not calibrating instruments?

Yes, there are several risks associated with not calibrating instruments. These include inaccurate measurements, which can lead to incorrect conclusions and decisions, as well as potential safety hazards if the instrument is used in critical applications. Additionally, not calibrating instruments can result in increased maintenance and replacement costs in the long run.

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