Time interval between the first interface echo after the excitation pulse and the first backwall echo. Using delay line or immersion transducers. Time interval between successive backwall echoes following the first interface echo after the excitation pulse. Using delay line and immersion transducers. 6V Rechargeable NiCad battery pack.
Active display shows percentage of remaining battery life.
Also when voltage is too low. Sealed color coded keypad with tactile and audible feedback. 5-Digit LCD with Backlight. Contrast keypad adjustable. Display blanks after last reading or holds reading.