– 36 –
Then
Voltage attenuation and phase change factor
= == Grid voltage Input voltage
where Wg? Lear = 1,
where = Dielectric constant of crystal
A= Attenuation due to viscosity of medium and geometrical causes.
RQw) = = ~ Big f ae 5 ig ore foot — + in on Se) oa ee) 20 20 29 2a 2 ig?
The quantity 7 depends only on the crystal, i.e. on the material of which it is made and its cut and form of excitation. Both £2 nd 1, zt of the dimensions of a pressure. 47 is of the dimensions of an electric field, and may be thought of as a constant electric field which has to be added to the varying field in order that the combination should produce the correct pressure variations, somewhat like the permanent magnet field in a telephone receiver, A typical
value for qin ors HES is 0.004.
Let us now consider the frequency-dependent factor, R(w). The parameter u entering here is the ratio of the characteristic impedances of the crystal and the liquid, It is equal to
