The figure illustrates the desired characteristics for maintaining the same level of protection over the frequency range that can be anticipated for battery powered vehicle charging systems, considering devices with an I∆n of 6 mA, 10 mA, and 30 mA.Figure 1 – Desired characteristics for maintaining the same level of protection over the frequency range9.7.2 Test circuitThe IC-CPD is connected as for normal use, unless otherwise specified. The reset of the IC-CPD may be made with any suitable method.The instruments for the measurement of the residual current shall show (or permit to determine) the true r.m.s. value.The instruments for the measurement of time shall have a relative error not greater than 10 % of the measured values. Unless otherwise specified, the tests are performed at the reference temperature of 20 °C ±5 °C and with no load.The IC-CPD shall perform the tests of 9.7.3, 9.7.4, 9.7.5, 9.7.6, 9.7.7, 9.7.8, 9.7.9, 9.7.10, 9.7.11 and 9.7.12. Each test is made on one pole only, taken at random, with five measurements, unless otherwise specified.For IC-CPDs having more than one rated frequency, the tests shall be carried out at the lowest and highest frequency.