Example: an N-80 reference field for a survey-meter energy-response test
Field Pro · updated 28 October 2026
An energy-response test of an H*(10) dose-rate meter needs reference beams whose spectrum is known well enough to name the conventional quantity value at the test point. N-80, from the narrow-spectrum series of ISO 4037-1, is one of the qualities such tests step through. This example sets it up, checks it against the table and turns a chamber reading into the value the meter under test should show.
Inputs
Open the workbench with the N-80 preset; these are also the defaults.
| Panel | Field | Value |
|---|---|---|
| 01 Source | Source / ISO beam quality | X-ray tube / N-80 |
| 01 Source | Tube voltage | 80 kV |
| 01 Source | Filtration | 4 mm Al (inherent) + 2 mm Cu |
| 01 Source | Air path | 2500 mm |
| 02 Geometry | α / HVL material / ISO comparison / band | 0° / Auto / Auto-match / ±5% |
Results
| Quantity | Workbench | ISO 4037-1 (2.5 m) | Deviation |
|---|---|---|---|
| Mean energy Ē | 64.96 keV | 65.2 keV | −0.37% |
| Effective energy Eeff | 63.95 keV | — | — |
| HVL1 | 0.5753 mm Cu | 0.580 mm Cu | −0.80% |
| HVL2 | 0.6185 mm Cu | 0.623 mm Cu | −0.72% |
| Homogeneity coefficient h | 0.9302 | 0.9310 | −0.08% |
| Air-kerma transmission of the 2 mm Cu | 1.51% | — | — |
| H*(10)/Ka | 1.723 Sv/Gy | — | — |
| Hp(10, 0°)/Ka, slab | 1.876 Sv/Gy | — | — |
| Hp(10, 60°)/Ka, slab | 1.496 Sv/Gy | — | — |
| H′(0.07, 0°)/Ka | 1.592 Sv/Gy | — | — |
Panel C matches N-80 automatically and puts all four characteristics inside the ±5% band.
From chamber reading to conventional value
Suppose the reference chamber, after its own calibration factor and kρ, gives an air kerma rate of 1.00 mGy/h at the test point. The conventional ambient dose equivalent rate the meter should indicate is 1.00 × 1.723 = 1.72 mSv/h. The meter's relative response at this quality is its indication divided by 1.72 mSv/h, and that ratio is what the type-test limits apply to. The IEC 60846-1 summary on RadiMeter lists those requirements.
What the numbers say
HVL is the sensitive check; the conversion coefficient is not. Moving the tube voltage by 2 kV in the workbench shifts HVL1 from 0.5753 to 0.5555 mm Cu at 78 kV (−3.4%) and to 0.6008 at 82 kV (+4.4%). A 0.1 mm error in the copper moves it by about 1.5% either way. Across all four of those changes H*(10)/Ka stays between 1.722 and 1.724 Sv/Gy. A measured HVL1 outside the band therefore tells you the beam is not N-80 as specified, usually through kilovoltage or filtration, long before the dose conversion itself is in doubt.
Average over the spectrum. Reading the monoenergetic table at Ē = 64.96 keV would give 1.735 for H*(10)/Ka and 1.893 for Hp(10, 0°)/Ka, 0.7% and 0.9% above the spectrum averages. In a test whose limits are tens of percent that is small, but it is a systematic error with a known sign, and there is no reason to carry it.
Output costs filtration. The 2 mm of copper lets through 1.51% of the air kerma that the inherent filtration alone would deliver, about a factor of 66. Plan tube current and distance with that in mind before booking beam time; the kerma overlay on the spectrum chart shows that 80% of what remains lies between 55 and 75 keV, peaking at 67 keV.
Angle matters for personal dosemeters. For a personal dosemeter tested on the slab at 60°, the conversion coefficient drops to 1.496 Sv/Gy, 20% below normal incidence. Set α in panel 02 to the angle of each irradiation rather than correcting by hand.
The same steps for a nuclide field are in the Cs-137 example, and the Guide explains each panel.
Sources
- ISO 4037-1:2019, Table for the N series: N-80, 80 kV, 4 mm Al inherent and 2 mm Cu added filtration, mean energy 65.2 keV, HVL1 0.580 and HVL2 0.623 mm Cu at 2.5 m.
- ISO 4037-3:2019, Tables 14 and 46: monoenergetic h*K(10) and hpK(10; α) used for the spectrum averages.
- IEC 60846-1:2009, Radiation protection instrumentation — Ambient and/or directional dose equivalent (rate) meters and/or monitors for beta, X and gamma radiation — Part 1: Portable workplace and environmental meters and monitors.
- Workbench values computed with the published engine on 28 October 2026; formulas on the Methods page.