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User Manual California Instruments
6.5Output Impedance Calibration
Note: Applies to NSG 1007-3, NSG 1007-5-208, NSG 1007-9, and NSG 1007-15-208 models
only.
For the output impedance calibration, one or two HP 34401A DMM's or equivalent may be used.
The following modes must be programmed: 6 digits, AC Filter, slow: 3 Hz and 6 digits. One
DMM is used to measure the output voltage, one to measure the load current using a suitable
CT. A single DMM may be switched between front and rear inputs to toggle between voltage and
current measurements.
The calibration should be done for each phase individually. Furthermore, an accurate phase
meter with at least 0.01° resolution is needed. (See equipment list section 6.1). The reference
input of the phase meter must be connected to the LOCK output of the controller at the rear
panel of the master NSG 1007-5-208 chassis. This is a square wave TTL signal. Select Square
wave input on the phase meter. The other input of the phase meter must be connected at the AC
source output of the phase being calibrated. Select Sine wave input on the phase meter for this
input. Note that this is a 230 Vrms signal so the Phase Meter must have sufficient input range on
this input. The phase meter is used to determine the phase shift between no load and full load
conditions (
∆Φ
).
The readings from the DMM's and Phase meter should be written down to aid with calculations.
A calculator is used to calculate the R and L portions of the impedance using the formulas shown
in Table 6-13.
To verify or adjust the programmable impedance function, proceed as follows for each phase:
1. Program the power source to 230.0VAC and 50Hz.
2. Program the output impedance resistance and inductance to the lowest values from the
OUTPUT IMPEDANCE screen. This will be the IMP. REAL MIN and IMP. REACT MIN
values that have been set in the OUTPUT CAL screen. Press the PHASE key to select the
phase to be calibrated. (A, B or C).
3. Measure the output voltage of the power source with no load and record this value (V
NL
).
4. Using a resistive load bank, load the output of the power source to about 16 amps. Measure
the output voltage of the power source under load and record this value (V
L
). Also measure
the load current and record this value. (I).
5. Calculate the resistive and inductive component R and L using the formulas shown in Table
6-13.
6. Enter these values, in the OUTPUT CAL screen for the IMP. REAL MIN and IMP. REACT
MIN value respectively. Make sure the correct phase is selected or use the PHASE key if
not.
7. Remove or turn off the load.
8. From the MENU 3 screen, select OUTPUT IMPEDANCE. Press the PHASE key to select
the phase to be calibrated. Program the output inductance to 796 uH and the resistance to
400 mOhms.
9. Select the Calibration, Output screen and move the cursor to the IMP REAL FS field.
Measure the R and L by removing and applying the load as described before and calculating
the R and L using the formula's in Table 6-12.
Adjust the resistive output impedance using the shuttle until the measured output is as close
as possible to 400 mOhm. Make sure the correct phase is selected or use the PHASE key if
not. Do the same with the IMP REACT FS field. Note that the adjustment range for R is 0 to
100, for L is 0 to 300.
146 i Series II / NSG 1007 II / iM Series II