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Instructions for Bench Use
The 944i is delivered ready for bench operation. The unit is equipped with front tilt feet to adjust viewing angle. The 944i is also
equipped with side handles to assist in carrying the unit. Use caution when lifting, the 944i is surprisingly heavy. Hold handles
toward the rear of the unit for best balance. Always verify that the power cord is equipped with a three terminal connector before
applying power to the 944i.
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Instructions for Rack Mounting
Optional rack mounting brackets are available for mounting the 944i in a standard 19" equipment rack. The size and weight of the
944i require that the unit should be supported on both sides along its entire length by the use of trays or slides. If it is to be
transported while mounted in a rack, it must be supported to prevent upward or downward movement.
To install the RM-1 rack mount kit, remove the two forward flathead screws on each side of the 944i. Position the rack ears in
place and install with the provided 5/8 inch 8-32 flathead screws. CAUTION! Longer screws may damage the unit. The
specifications for the 944i become degraded at high temperatures, therefore it is recommended sufficient room be allowed for
airflow around the 944i. This may be achieved by placing at east 1.75" high blank panels above and below the 944i in the rack.
Under no circumstances should the ambient air temperature surrounding the 944i be allowed to exceed 50° C while in operation or
70° C while not in operation.
Earth Ground Connection
The power connector should be a three-contact device meeting the safety requirements of the area in which the 944i is to be used
and should only be mated with a three-contact connector where the third contact provides ground connection. If the power is
provided through an extension cable then the ground connection must be continuous throughout this cable to the 944i.
FAILURE TO PROVIDE A CONTINUOUS GROUND CONNECTION TO THE 944i MAY RENDER THE UNIT
UNSAFE FOR USE.
Current Detection Circuitry
The 944i is equipped with three separate circuits for the monitoring and measurement of the output current. For precision
measurement, the 944i utilizes an RMS measurement circuit based on a 12 bit ADC. When load failures are detected using the
RMS circuit, a typical failure message would be "failed-max I" or "failed-min I".
For high-speed detection of load breakdown, the 944i utilizes a peak current comparator circuit which is set to trip at
approximately 50 mA peak. When sudden breakdown occurs, the peak detection circuit will generally trigger before the slower,
precision RMS measurement circuit. The failure message for the over current circuit is "Failed-OVR Current".
The final circuit which the 944i contains for catching load failures is a user programmable arc detector. The arc detector checks
for small current pulses using a DIDT comparator circuit. The user selectable arc detection modes of "fast", "medium", and
"slow" equates to arc pulse width of approximately 3, 10 and 30 micro seconds. The failure message of the arc detector is "Failed-
Arc".
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