Meggitt VM600 - Shaft Collar Method

VM600 MPS hardware manual (standard version) MAMPS-HW/E 7 - 15
Edition 17 - February 2018
Shaft relative expansion
PROCESSING MODES AND APPLICATIONS
7.9.1 Shaft collar method
(1) Description
Two probes are used in this configuration, with one probe placed on each side of a shaft collar
(see Figure 7-11). Two possibilities exist:
• Both probes are operating in their measuring range at the same time.
• The probes are operating alternately, with only one probe in its measuring range at a
given time. This doubles the measuring range that is possible with a single probe.
a. When both probes are in their operating range at the same time:
If GAP1
i
and GAP2
i
are the respective initial gaps, then:
ΔL = (GAP1  GAP2) / 2  (GAP1
i
 GAP2
i
)/2
If initial gaps are equal, the differential expansion is:
ΔL = (GAP1  GAP2) / 2
b. When the probes are operating alternately:
ΔL = (GAP1
 GAP1
i
) in the operating range of probe 1.
ΔL = (GAP2
i
 GAP2) in the operating range of probe 2.
Figure 7-11: Two proximity probes mounted near a shaft fitted with a collar