An electronic device (60; 62A,..., 62N) for monitoring an electrical quantity from among a voltage (U1, U2, U3) and a current (I1A,..., I3N) relating to an alternating current flowing in an electrical conductor (34, 36, 38; 42A, 44A, 46A,..., 42N, 44N, 46N), the alternating current having at least one phase, the device comprising: - a measurement module (66; 76A,..., 76N) configured to measure at least one value of the electrical quantity, - a sampling module (103; 119A,..., 119N) configured to sample the value of the measured electrical quantity, - a radio transceiver (70; 80A,..., 80N), - a transmission module (106; 128A,..., 128N) connected to the radio transceiver (70; 80A,..., 80N), the transmission module (106; 128A,..., 128N) being configured to transmit data messages (M1; M2A,..., M2N) to another electronic device, with a transmission period (P transmission) separating the instants of transmission of two successive data messages, each data message (M1; M2A,..., M2N) containing a set of at least one parameter for monitoring the quantity measured, said set comprising coefficients of a transform of the measured values, - a module (104; 123A,...,123N) for determining a first table (TABLE_1) and a second table (TABLE_2), and a module (105; 121A,... 121 N) configured to calculate at least one parameter for monitoring the quantity on the basis of the first table (TABLE_1), the second table (TABLE_2), and samples of the quantity, taken from the sampling module (103, 119A..., 119N), the first table (TABLE_1) containing a plurality of first coefficients (C 1 j,m), each first coefficient (C 1 j,m) being a function of a cosine and dependent on the frequency F of the voltage of the electrical conductor (34, 36, 38; 42A, 44A, 46A,..., 42N, 44N, 46N), and the second table (TABLE_2) containing a plurality of second coefficients (C 2 j,m), each second coefficient (C 2 j,m) being a function of a sine and dependent on said frequency F, the device being characterised in that the number of coefficients (C 1 j,m, C 2 j,m) of each table (TABLE_1, TABLE_2) is equal to the number of samples of the quantity during the transmission period (P transmission) and the transmission period (P transmission) corresponding to a multiple (N voltage) of voltage periods (P voltage), the multiple (N voltage) being a real number with a value strictly greater than 1, the number of samples of the quantity during the transmission period (P transmission) being equal to the transmission period (P transmission) divided by the voltage period (P voltage) and multiplied by a number of samples of the quantity measured per voltage period (P voltage), the first and second tables being calculated for the entire broadcast period (P transmission). - a measurement module (66; 76A,..., 76N) configured to measure at least one value of the electrical quantity, - a sampling module (103; 119A,..., 119N) configured to sample the value of the measured electrical quantity, - a radio transceiver (70; 80A,..., 80N), - a transmission module (106; 128A,..., 128N) connected to the radio transceiver (70; 80A,..., 80N), the transmission module (106; 128A,..., 128N) being configured to transmit data messages (M1; M2A,..., M2N) to another electronic device, with a transmission period (P transmission) separating the instants of transmission of two successive data messages, each data message (M1; M2A,..., M2N) containing a set of at least one parameter for monitoring the quantity measured, said set comprising coefficients of a transform of the measured values, - a module (104; 123A,...,123N) for determining a first table (TABLE_1) and a second table (TABLE_2), and a module (105; 121A,... 121 N) configured to calculate at least one parameter for monitoring the quantity on the basis of the first table (TABLE_1), the second table (TABLE_2), and samples of the quantity, taken from the sampling module (103, 119A..., 119N), the first table (TABLE_1) containing a plurality of first coefficients (C 1 j,m), each first coefficient (C 1 j,m) being a function of a cosine and dependent on the frequency F of the voltage of the electrical conductor (34, 36, 38; 42A, 44A, 46A,..., 42N, 44N, 46N), and the second table (TABLE_2) containing a plurality of second coefficients (C 2 j,m), each second coefficient (C 2 j,m) being a function of a sine and dependent on said frequency F, the device being characterised in that the number of coefficients (C 1 j,m, C 2 j,m) of each table (TABLE_1, TABLE_2) is equal to the number of samples of the quantity during the transmission period (P transmission) and the transmission period (P transmission) corresponding to a multiple (N voltage) of voltage periods (P voltage), the multiple (N voltage) being a real number with a value strictly greater than 1, the number of samples of the quantity during the transmission period (P transmission) being equal to the transmission period (P transmission) divided by the voltage period (P voltage) and multiplied by a number of samples of the quantity measured per voltage period (P voltage), the first and second tables being calculated for the entire broadcast period (P transmission).