ASTM C597:16 pdf free download – Standard Test Method for Pulse Velocity Through Concrete.
6. 1 .2 Receiving Transducer and Amplifier—The receiving transducer shall be similar to the transmitting transducer. The voltage generated by the receiver shall be amplified as necessary to produce triggering pulses to the time-measuring circuit. The amplifier shall have a flat response between one half and three times the resonant frequency ot the receiving transducer.
6. 1 .3 7biie -Measu ring Circuit—The time-measuring circuit and the associated triggering pulses shall be capable of providing an overall time-measurement resolution of at least I is. Time measurement is initiated by a triggering voltage from the pulse generator, and the time measuring circuit shall operate at the repetition frequency of the pulse generator. The time-measuring circuit shall provide an output when the received pulse is detected, and this output shall be used to determine the transit time displayed on the time-display unit. The time-measuring circuit shall be insensitive to operating temperature in the range from 0 to 40°C and voltage changes in the power source of ± 15 %.
6.1.4 Display Unit—A display unit shall indicate the pulse transit time to the nearest 0. 1 is.
6.1.5 Reference Bar—For units that use manual zero-time adjustment, provide a bar of metal or other durable material for which the transit time of longitudinal waves is known. The transit time shall be marked permanently on the reference bar. The reference bar is optional for units that perform automatic zero-time adjustment.
6.1.6 connecting Cables—Where pulse-velocity measurements on large structures require the use of long interconnecting cables, use low-capacitance, shielded, coaxial cables
6.1 .7 coupling Agent—A viscous material (such as oil, petroleum jelly, water soluble jelly, moldable rubber, or grease) to ensure efficient transfer of energy between the concrete and the transducers. The function of the coupling agent is to eliminate air between the contact surfaces of the transducers and the concrete. Water is an acceptable coupling agent if ponded on the surface, or for underwater testing.
7. Procedure
7. I Functional Check of Equipment and Zero -time Adjustment—Verify that the equipment is operating properly and perform a zero-time adjustment.
7. 1 . I Units with Automatic Zero-fine Adjusinwut— -Follow the manufacturer’s instructions for performing zero-ti me adjustments.
Nom 8—A reference bar may be used to verify that the zero-time adjustment has been pertrmed correctly.
7. 1 .2 Units with Manual Zero-Time Adjustment—Apply coupling agent to the ends of the reference bar, and press the transducers firmly against the ends of the bar until a stable transit time is displayed. Adjust the zero reference until the displayed transit time agrees with the value marked on the bar.
7.1.3 Check the zero adjustment on an hourly basis during continuous operation of the instrument, and every time a transducer or connecting cable is changed. If zero-time adjustment cannot be accomplished, do not use the instrument until it has been repaired.