The Instek GPT-9903A is built upon a platform of AC 500VA maximum power output. The GPT-9903A is a 3-in-1 model capable of performing AC withstanding, DC withstanding and insulation resistance tests. The GPT-9903A's high-efficiency PWM amplifier is the core of the platform design to impede the influence from the voltage fluctuation of input AC source. The output voltage is automatically cut off (within 150μs) upon the detection of an abnormal output voltage or a trip of current limits during test to protect the operator from hazardous injury. The GPT-9903A automatically discharges the DUT after each test to eliminate excessive voltage that remains on the DUT.

Following a tidy and easy-to-use design concept, the GPT-9903A is equipped with a simple & clear panel layout, a high resolution dot matrix LCD display, and color LED indicators, allowing operators to interpret measurement results easily and quickly. The GPT-9903A is designed upon a 500VA output platform to enhance all major test functions, including AC withstanding (AC 5kV/100mA), DC withstanding (DC 6kV/20mA), insulation resistance (DC 50V - 1000V/50GΩ max.) and ground bond (AC 32A max./650mΩ max.) tests, with high-power measurement capabilities. Further more, the test duration, ramp up time and upper/lower limits of the output voltage are fully-adjustable to accommodate a wide variety of safety tests with accurate measurement results. The "Sweep" function of the GPT-9903A is able to display the test results point by point all through the testing period to form a trace graph. This graphic display performs the characteristic verification of a DUT through observing the parameter response to the changes of the applied voltage or current or testing time. On the graph a movable marker is available to get the parameter reading on the specific point of user's interest.

Other significant functions and features of the GPT-9903A series include the rear panel output for system applications, the open-circuit detection to ensure proper connections of apparatus for ground bond test, 100 sets of memory to save and recall the panel settings for individual or sequential tests, a remote output on-off terminal in the front panel and a signal I/O port in the rear panel provided as the means for remote start/stop control of the safety tester, and RS-232C, USB and GPIB (optional) interfaces available for PC remote control and test result logging.