Siemens Milltronics MFA 4p Operating Instructions Manual page 43

The graph was plotted from tests using four ferrous blocks set equidistantly on a 406 mm
(16 inch) diameter circle on a non-ferrous disc.
The physical shape of the ferrous target generally becomes important at low velocities or
large gaps. At these points, tests indicate that a cubic shape gives the best results due to the
sudden change it causes in the magnetic field.
An increase in block size beyond 50 x 50 x 25 mm (2 x 2 x 1 inch) is generally not as
effective as minimizing the gap, except at very low velocities.
Milltronics manufactures probes to suit a wide variety of environments: low temperature, high
temperature, corrosive, and Class I, II, and III applications.
Pre-Amplifier (IMA and RMA)
The pre-amplifier accepts the voltage pulses generated by the probe and converts them into
noise-immune current pulses. Current levels are 12 mA low and 45 mA high. The
preamplifier comes internally mounted in the probe, or in an enclosure for remote mounting.
Internally mounted pre-amplifiers are called IMAs. Remote mounted pre-amplifiers are called
RMAs.
Milltronics MFA 4p
Operating Instructions, 08/2017, A5E33988839_AB
Technical Reference
A.1 Principles of Operation
41