HBM HBK U93, Mounting Instructions

Page: 11 / 88

9
U93
STRUCTURE AND MODE OF OPERATION
4 STRUCTURE AND MODE OF OPERATION
4.1 Measuring body
The measuring element is a stainless steel, loaded member, to which strain gages (SG)
are applied. The SG are arranged so that two are stretched and the other two com­
pressed when a force acts on the transducer.
4.2 Strain gage covering
To protect the SG, the U93 force transducers are welded at an appropriate place with a
thin metal plate. This procedure offers the SG a high protection against environmental
influences. In order to retain the protective effect, this plate must not be damaged in any
way;
see section 6.2 on page 11 .
5 CONDITIONS ON SITE
Protect the transducer from extreme moisture and dampness, weather conditions such
as rain, snow and ice, and salt water.
5.1 Ambient temperature
The temperature effects on the zero signal and on the sensitivity are compensated.
To obtain optimum measurement results, the nominal (rated) temperature range must be
observed. Constant, or very slowly changing temperatures are optimal. Temperature‐re­
lated measurement errors are caused by heating on one side (e.g. radiant heat) or by
cooling. A radiation shield and all‐round thermal insulation produce noticeable improve­
ments, but must not be allowed to set up a force shunt.
5.2 Moisture and humidity
Series U93 force transducers are hermetically weld‐sealed, giving them degree of protec­
tion IP67 per DIN EN 60529 (test conditions: 100 hours under 1m water column). Never­
theless, the force transducers must be protected against permanent moisture influence.
Notice
Moisture must not be allowed to penetrate the free end of the connection cable. Otherwise
the characteristic values of the transducer could vary, and cause measurement errors.