A system for monitoring a biological sample, comprising: a. a container with a chamber, wherein the chamber contains a fluid and the biological sample is immersed in the liquid; b. a transmitter configured to output acoustic waves, in response to a drive signal, through the biological sample located in the chamber and immersed in the fluid; c. a receiver positioned to detect the acoustic waves transmitted through the biological sample located in the chamber and immersed in the fluid, the receiver configured to output a signal; d. a signal processing circuit to receive the signal output from the receiver; and e. a microprocessor configured to provide the drive signal that triggers a burst of acoustic waves and further configured to evaluate the output signal of the signal processing circuit to determine a property of the acoustic waves detected at the receiver, the property being indicative of a level of impregnation of the biological sample with the fluid in the chamber of the container; characterised in that the signal processing circuit comprises: i. an input gain and offset circuit component that produces a second signal, ii. a comparator component that compares the second signal to a reference voltage to produce a third signal, iii. a current source, iv. a switch and slew rate component, the switch and slew rate component controlling the current source in response to receiving the third signal from the comparator component, and v. a hold capacitor that is charged by the current source until reaching a maximum, the maximum representative of the peak amplitude of the acoustic wave arriving at the receiver and serving as an output signal. a. a container with a chamber, wherein the chamber contains a fluid and the biological sample is immersed in the liquid; b. a transmitter configured to output acoustic waves, in response to a drive signal, through the biological sample located in the chamber and immersed in the fluid; c. a receiver positioned to detect the acoustic waves transmitted through the biological sample located in the chamber and immersed in the fluid, the receiver configured to output a signal; d. a signal processing circuit to receive the signal output from the receiver; and e. a microprocessor configured to provide the drive signal that triggers a burst of acoustic waves and further configured to evaluate the output signal of the signal processing circuit to determine a property of the acoustic waves detected at the receiver, the property being indicative of a level of impregnation of the biological sample with the fluid in the chamber of the container; i. an input gain and offset circuit component that produces a second signal, ii. a comparator component that compares the second signal to a reference voltage to produce a third signal, iii. a current source, iv. a switch and slew rate component, the switch and slew rate component controlling the current source in response to receiving the third signal from the comparator component, and v. a hold capacitor that is charged by the current source until reaching a maximum, the maximum representative of the peak amplitude of the acoustic wave arriving at the receiver and serving as an output signal.