STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

MWD and LWD 907
Coils
Po
Figure 4-220. Schematic diagram of a servo-controlled single-axis
accelerometer.
THIN FILM PICKOFF AN0
TOROUER LUOS
ELECiRONlCS
DAMPING GAPS
PICKOFF PUIE
(a)
(b)
Figure 4-221. Servo-controlled “single-axis” Sunstrand accelerometer:
(a) accelerometer photograph; (b) exploded view of the accelerometer.
(Courtesy Sunstrand [ 1 021.)
all the errors, and their variation with temperature. In this case, the accelerometer
temperature must be known. The maximum current feedback defines a
measurement range beyond which the accelerometer is saturated. Vibrations
must be limited in order not to disturb the accelerometer response.
Assume that the accelerometer has the ideal response shown in Figure 4-223,
with a measurement range of 2 g (32.2 ft/s2). We want to measure 1 g, but the
ambient vibration level is f3 g. In this case, the accelerometer’s indications
are shaved and the mean value obtained is not 1 g but 0.5 g. The maximum
acceleration due to vibrations which are not filtered mechanically, plus the