188 



MEASUREMENT OF PRESSURES 



formance of terminating networks by a-c measurements, and for com- 

 parison with such measurements it is more convenient to rewrite Eqs. 

 (5.13) in the form 



(5.14) 



1 _ 1 (^ sin Rod 



Vtico) ~ OoVo} RoCc^ 



1 +MRiCi + R2C2) - c^KRo" + RiR2)CiC2 



+ (Ci + C2) cos RoCc. Tl + MR, + R2) -^^]\ 



2.0 



Uj 1.5 

 </) 



z 

 o 

 o. 

 </) 



UJ 



1.0 



U 0.5 



0.2 



0.5 1.0 2.0 



REDUCED FREQUENCY RCU) 



5.0 



Fig. 5.19 Frequency response of piezoelectric gauge circuit for various cable 



terminations. 



It is easily seen that this expression reduces, for low frequencies, to the 

 value obtained by considering only the capacitances in the circuit: 



Yi 



CoVc 



C + Ci + C2 



Some special values of terminating network parameters will now be 

 considered to illustrate more specifically the circumstances under which 

 compensation becomes important and the improvement obtainable with 

 two types of compensation. 



(1). Capacitance only at receiving end {Ri = R2 = Ci = 0). The 

 steady response predicted by Eq. (5.14) reduces to 



