User manual

ACM
The ACM electronics housing contains compass and tilt sensors. Figure 2-12 shows the
FSI Acoustic Current Meter (ACM). The ACM communications and power cable connects to the
controller housing end cap through the central hole in the bottom rib of the frame. The CTD and
ACM connectors are physically (and electrically) identical, so the cables and connectors are color
coded to avoid confusion (deploying with incorrectly connected cables could prevent data
collection).
Figure 2-12: ACM Sting
The ACM must be properly aligned and secured within the MMP frame so that the
relative path velocities measured by the sensor can be rotated into a Cartesian earth frame during
post-processing. The ACM sting has four “fingers” extending at a 45º angle away from a central
post (the sting extends well forward of the MMP body so that its measurement is made in
relatively undisturbed flow). The fingers are labeled +X, +Y, -X, -Y.
Mount the sting with the -Y finger up. After the sting base plate is placed and the four
bolts have been finger-tightened as shown in Figure 2-13, twist the sting and align it so that the
+Y and -Y fingers lie on a vertical plane and the +X and -X fingers lie on a horizontal plane.
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