What does the Energy Response Graph represent? Posted on April 18, 2018 The Energy Response Graph shown in the operation manual gauges how the instrument will respond to various energies. GM detectors cannot distinguish different types of energies, but we can gauge how the detector responds to them. Monitor 200 & Monitor 4 Energy Response To Gamma Cs137 For example, on the graph shown above, the M4 Sidewall response starts at 30 keV with a relative count rate of 3. An isotope giving off radiation at 30 keV might cause the GM tube to over respond by 3X. This means the detector may be reading that there is three times the exposure present. At its highest peak, the meter will over respond showing 7 times the rate at 60 keV. The Monitor 4 will start to have a relative response of 1 at about 500 keV.