# X-ray equipment: Constant potential 200-500 KV: Fig 3.2 (4)

**Published:** Sep 29, 2021

**If you take the y-axis value and multiply by 600, this will give you a figure of mGy/ mA h at 1m**. Note how exposure rate is significantly affected by filtration.

The handbook suggests that for half wave generators, the output is about 1/3 to 1/2 of that plotted.

In SI units R has the units of charge divided by unit mass (C/kg). C (coulomb) is the amount of electric charge transported by a current of 1 ampere during 1 second.

1 R is the amount of radiation required to liberate positive and negative charges of one electrostatic unit of charge (about 3.33564×10^{−10} C) in 1 cm³ of air at standard temperature and pressure (STP).

In air, 1 R = 2.58×10^{−4} C/kg. 100 R is 0.933Gy at STP in air (i.e. 1Gy is a good approximation).