Transducer Snubbing

Transducer snubbing need no longer be guesswork. Using our new Lohm law for snubbers it is easy to select the correct Visco snubber for every application. Typical applications involve snubbing a cyclic pressure ripple superimposed on a steady pressure. The graph below together with the formula below provide a rapid means of calculating the necessary Lohm rate.

TO FIND A LOHM RATE
Decide how much attenuation is required and use the graph below to obtain a value for f_o . Use this in the formula below and solve for Lohm rate.

L = Fluid resistance (Lohms)
f_o = Frequency from graph (Hz)
f_r = Ripple frequency (Hz)
v* = Internal volume of the transducer (in³)
B = Fluid bulk modulus (psi)
K* = Transducer compliance (in3/psi)
P_o = Ripple amplitude, peak-to-peak (psi)
*Obtainable from the transducer manufacturer.

EXAMPLE
A pressure transducer is being damaged by a pump ripple of 270 Hz. The peak-to-peak amplitude is 1000 psi. Knowing the transducer has an internal volume of 0.09 in³ (1.5 mL) and a compliance of 3 x 10-7 in3/psi, which Visco snubber is required to reduce the ripple to 1/20 of the unsnubbed amplitude? The fluid is Skydrol with a bulk modulus of 340,000 psi.

Obtain f₀ from the graph (170 Hz at 0.05 amplitude ratio.) Then use the formula:

Use Visco snubber Part Number VHSA1250800H (80,000 Lohms).

ATTENUATION CHART