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Operating the Vitrek 944i in direct mode permits the user to manually control the output up or down while monitoring the leakage
current being drawn by the load. When operating in the direct mode the user is in full control of the measurement process - ramp
rate and dwell time are a function of how fast the user changes the output voltage and how long the user chooses to stay at that
setting. Voltage and current limits are set by the user to prevent accidental excursion beyond those preset points.
DC Dielectric Strength Function
In evaluating the ability of materials to insulate against the flow of electricity, the DC Dielectric Strength Test is extremely
valuable. The DC test function specifically analyzes the ability of a material to resist the flow of direct current in the presence of a
high voltage. Other common names for the DC Dielectric strength test include: DC Hipot, DC Voltage Breakdown and DC
Voltage Withstand.
To gain access to the DC Dielectric test mode, simply press the VDC button located under the display window. Upon pressing the
VDC button, the following display prompt will appear:
DC DIELECTRIC TEST
DIRECT
AUTOMATIC
This message confirms that the DC function has been selected and offers two different operating modes. By using the left/right
cursor arrows, one can alternatively highlight either Direct mode or Automatic mode.
Direct mode permits manual operation and is highlighted when the Direct/Automatic menu pops-up. To select Direct mode,
simply press enter. The following prompt will appear:
ENTER MAX VOLTAGE
1000
VOLTS
This prompt allows the operator to set a maximum test voltage. This limit prevents the user from inadvertently exceeding the
intended range of output voltage. The 1000 VDC shown is the default limit. To enter another limit, simply press the number keys
for the desired value. The range of limits for the VDC function may be as low as 100 VDC or as high as 5000 VDC. Once the
desired voltage limit is displayed, press enter to advance to the next step.
The last setup prompt in VDC direct mode is the current limit prompt as shown below:
ENTER MAX CURRENT
10.0
mA
This value sets the maximum amount of leakage current, which the 944i will source without 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 100 nA 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 VDC 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.
