function correctly these verifications are used during each startup of the device i e each time that the value of the high voltage passes from a zero value to a non zero value which guarantees a large number of verifications during a workday an eventual malfunction is thus detected without delay the verification could also be based on the value of the high voltage u ht created in the sprayer 5 i e between electrode 9 and circuit ground or based on either the current or the voltage supplied to generator 3 or on any other physical quantity representative of the operation of the device and in particular representative of the high voltage current one can note that the invention permits detection of improper operation of each of the components 12 13 and 14 and or the circuits 11 and 17 it can even permit detection of a malfunction of the calculator 20 if provision is made to activate the alarm 21 or the shut off means 22 by default i e on a fail safe basis unless the signals produced at the outputs of calculator 20 based on measurements of i ht and of di ht dt have suitable.