MI 3290 Earth Analyser
Technical specifications
134
15.4 Impulse Impedance [Zp]
15.4.1
Impulse Measurement
Measurement principle: ............................... Voltage (peak) / Current (peak) measurement
Impulse Impedance Measuring range
Resolution
Uncertainty
Zp
0,0
… 19,9
0,1
(8 % of r 8 digits)
20
… 199
1
Test mode ...................................................... single
Open-terminal test voltage ........................... ~120 V
peak
Short-circuit test current ............................... ~6 A
peak
Impulse waveform ......................................... 10 / 350 µs
Zp Definition .................................................. The peak voltage divided by the peak current.
Limit range (Zp) ............................................. 1
… 100
(OFF)
Measuring time ............................................. typical 20 s
Automatic connection test ........................... yes [H, S, E]
Automatic test of probe resistance ............... yes (at 3,29 kHz)
Automatic test of voltage noise .................... yes
Guard terminal .............................................. yes
Influence of the auxiliary electrodes
The current probe Rc and potential probe Rp are measured using 3-Pole measurement at a fix frequency
3,29 kHz @ 40 Vac open-terminal test voltage.
Rc and Rp max
.
....................................................... (> 100 Ω + (40 * Ra)) or 1 kΩ (whichever is lower)
Additional error if Rc or Rp max. is exceeded ........
(20 % of reading)
Influence of noise
Max noise interference voltage on terminals H, S and E .................. 1 V rms
R1
R3
R
4
G
R
2
spark gap
C
L
Output
terminals
H
E
Figure 15.1: Simplified circuit of impulse generator in the MI 3290
where:
G ................................................................... High voltage source
R1 ................................................................... Charging resistor
C .................................................................... Energy storage capacitor
R2, R4 ............................................................. Impulse duration shaping resistors
R3 ................................................................... Impedance matching resistor
L ..................................................................... Impulse rise time shaping inductor
t [µs]
i [
A
]
Impulse shape
i max.
10 µs
i 50%
350 µs
Figure 15.2: Typical Impulse shape short-circuit
