device for metning of the time, which atgar went to the amplitude of a declining vexelspenning shall fall from a first, senior level to a second level, legre

摘要

The invention concerns an arrangement for measuring the time it takes for an amplitude of a decreasing alternating voltage to drop from a first, higher level to a second, lower level. The measurement arrangement according to the invention can be used to measure the reverberation time and it contains, first, a first level detector 7 for activating a counter 12 to count the pulses of predetermined pulse frequency arriving from a pulse generator 11 when the alternating voltage passes the first level, second, a second level detector 8 for deactivating the counter 12 when the alternating voltage passes the second level, and third, an indicator 13 for digital presentation of the reverberation time. According to the invention, the first level detector 7 contains a delay circuit C1, R10 to delay the activation of the counter 12 for a predetermined interval of time t. This ensures that the counter 12 is only activated when the amplitude of the alternating voltage has fallen below the first level during this interval of time. The second level detector 8 contains, according to the invention, a second delay circuit C11, R20 for delay of the deactivation of the counter 12 with the same predetermined interval of time t. This ensures that the counter is only deactivated when the amplitude of the alternating voltage has fallen below the second level during this interval of time. According to the invention, furthermore, an amplifier 6 is hooked up to amplify the input signal to the second level detector 8 in accordance with the difference between the first level and the second level. IMAGE