After the voltage limit has been set the 944i will prompt for a test frequency. This advanced feature, which enables the user to test
AC dielectric strength over a wide range of test frequencies, is unique to the Vitrek 944i. The frequency prompt is as follows:
SELECT
TEST
FREQUENCY
60 HZ
50 HZ _ _ _ HZ
Should the user desire a test frequency of 60 Hz, press enter. If 50 Hz is the desired test frequency, use the right cursor to
highlight the 50 Hz option and then press enter. When an alternate test frequency is required, use the cursors to highlight the _ _ _
Hz option and then use the number keys to fill in the frequency of interest and then press enter.
Following frequency selection, the current sense selection menu will appear as shown below:
SELECT CURRENT SENSE
REAL APPARENT
TOTAL
The Vitrek 944i uses internal phase angle circuitry to determine if the leakage current being measured is a result of a resistive load
(real), reactive load (apparent) or both (total). In most applications total current is the desired sense mode and is highlighted when
the current sense prompt pops-up. To select "total" press the enter key.
In many applications involving devices with EMI filters, the current being drawn by the filter capacitor is of no interest to the
user. To ignore the current flow caused by the reactive component, select the "real" current sense mode. To determine the
amount of current flow caused by the reactive component, select "apparent" current sense.
Due to the nature of phase measurement, it is difficult to accurately determine the phase of low amplitude signals. To prevent
erroneous phase measurement under low amplitude conditions, the 944i will automatically default to "total" current sense when
phase signals are below the minimum threshold.
Once the current sense mode has been selected, the 944i will prompt the user to set a current limit with the following message:
ENTER MAX CURRENT
10.0 mA
This value sets the maximum amount of leakage current which the 944i will source prior to shutting down the test. Any current
which exceeds this limit will cause the unit to automatically stop the test. The default value is 10.0 mA. However, any value
between 1nA and 35 mA may be used. To change the value of the current limit, use the number keypad. To change the units
from m (milli) to u (micro) or n (nano), use the up/down cursor arrows. Once the desired maximum current limit is displayed,
press enter to complete the test set-up for VAC Direct mode.
For safety purposes, the 944i requires a two step key press sequence prior to initiating high voltage testing. Before beginning this
sequence, it is important to ensure that the device under test is properly connected to the 944i test terminals. Please refer to the
"Test Connections" section of the operating manual before proceeding.
WARNING!, failure to observe safety precautions may
result in severe injury or death to the operator.
The display will prompt the user to press the HV enable key as follows:
HIGH VOLTAGE ENABLE
REQUIRED
Once the test connections have been verified, press the HV enable key. After pressing the high voltage enable key the final prompt
is:
PRESS ENTER TO
START
TEST
Upon pressing the enter key the 944i will sound a number of warning beeps while flashing the HV enable indicator. If the user
has enabled the auto-ground test feature of the 944i, the unit will automatically check the chassis of the DUT for earth ground
continuity before applying high voltage to the DUT.
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Insulation Resistance (Megaohm) Function
In addition to having AC and DC dielectric strength functions, the Vitrek 944i also offers the convenience of high resistance
measurement. To call the insulation resistance (megaohm) function, press the megaohm key. The following prompt will appear:
MEG OHM TEST
DIRECT
AUTOMATIC
