HBM K3607, Руководство по эксплуатации

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Effect of cable resistance
K3607
A0833-3.1 HBM: public
11
7 Effect of cable resistance
The cable effect for KAB0238A‐3 cable is calibrated in at the factory. This
applies to four‐ and six‐wire circuit at the end of the 3‐meter long cable.
On subsequent connection in four‐wire circuit, the output signal is reduced by
the K factor due to the resistance of the excitation wires.
The K factor is calcultated as follows:
Bridge resistance)
The resistance value of an excitation wire is used for the r term. In the case of
KAB0238A‐3 cable this resistance r = 0.0118

. According to the formula (1)
this gives a value of 0.99993 for the K factor. This means an absolute calibra­
tion error of 0.007% if KAB0238A‐3 is not used.
A switching step error also occurs. Depending on the position of switch S2 the
internal resistance of the K 3607 alters slightly, as does the effective excitation
voltage due to the cable resistance r.
The grading error of the percentage steps increases by some 0.02% at 10

of
cable conductor resistance.
When connecting a six‐wire circuit the cable effect is corrected and the K factor
= 1. No additional grading error occurs (internal excitation voltage resistance <
1

).
If KAB0238A‐3 cable is not used, an absolute calibration error of the corre­
sponding size occurs. This means the output signal is increased by a factor of
K = 1.00007.