Electrical Interference During Measurements In Laboratories - testo 252 Bedienungsanleitung

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Electrical interference during
measurements in laboratories
During measurements in grounded measuring
solutions, a measuring error can occur as a result
of the earth loops (galvanic and/or capacitive
coupling).
Not grounded measurement with mains
independant measuring instruments (to which no
complementary instruments are connected, e.g.
recorder) guarantees as a rule interference-free
operation. When using mains operated
instruments, a galvanic separation must be
installed for each instrument - this is particularly
valid when computer systems are connected. We
recommend the use of an optically-coupled
interface (article no. 0554.0006) in conjunction with
a PC adapter (article no. 0554.0071).
The simplest test methods for the user involve
dipping a sensor in a well-insulated solution and
then alternately ground and un-ground the
solution. Should the display change, there is a very
high disturbing current. It is useful in this case to
operate the instrument with batteries or rech.
batteries.
During parallel measurements (pH conductivity)
with testo 252 measuring instruments, please note
the following points:
• The measured value is only valid when
both probes are immersed in the
measuring solution.
• For low conductivity solutions (< 100 µS/cm)
glass/platinum cells should be used.
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