JANUARY 31 2003
A m m eter
D C Po wer S up ply
A dj ust ab le
R esis to r
V oltm et er
IR D rop
T est St at io n
P ip elin e or c ab le
Measurement Circuits. Calibration
of an IR Drop test span involves two
measurement circuits. The outside circuit comprises an ammeter to measure the
current, a DC power supply, an on/off switch and some means of adjustment. A
portable rectifier may be used as the current source, switch, and the means of
megaohms), set to the millivolt scale.
Pipelines and cables inherently will have current flowing at all times.
Therefore, a change in voltage drop measurement is compared to the amount of test
Following all polarities in Figure 7-34, connect all circuit components.
Polarity is important for correct determination of the direction of the current
flow in the pipeline or cable during subsequent test procedures.
With the outside circuit switch off, record the mV measurement of the
Starting at a low current level, turn the outside circuit switch on and adjust
current up to the desired test current. Record the measurement of the test