When moving a cable electrostatic charges and voltages occur due to internal friction. As these voltages, called microphony, may have up to 0.5 V, the actual measured signal will be blotted out.
Low noise measuring cables made by bedea are designed to emit extremely low microphony voltages, in specially constructed cables the microphony voltage is even below 0.1 mV. The quality of the potential balancing layer is essential for this advantage in the measuring technology.
For special applications, these cables may be combined with power supply or control cores and additional screenings.
Measuring procedure
Up to now, there was only one test procedure specified in the international standardisation, the procedure according to Mil-C-17-G, 4.8.14. The disadvantage of this procedure is the insufficient reproducibility and the low sensitivity.
In cooperation with the University of Technology, TH Darmstadt, bedea developed a new test procedure which is standardized as IEC 61196-1, Amendment 1:1999. This new test procedure allows to determine microphony charges and loads precisely with high sensitivity.
Measuring procedure
1 Generator, 0 Ð 20 kHz
2 Power amplifier
3 Vibrator
4 Accelerometer
5a Charge amplifier with extra double integrating 5b Charge amplifier
6a Oscilloscope, elongation measurement 6b Oscilloscope, microphony charge
(level) measurement
7 Test rig
8 Cable under test (CUT)