DC ELECTRONIC LOADS

VXIbus LOAD

• 50 W / 75 V, 1 or 10 A
• Glitch-free transitions from constant resistance to constant current operation
• Selectable current slew rates

APPLICATION

Model 81201 and 81210 VXIbus DC electronic loads are designed for low-power devices such as DC power supplies which need loads capable of both static and dynamic modes of operation. Each DC load is a self-contained instrument on a single-slot, C-size VXIbus module making them ideal for applications where tester rack space is limited and a VXIbus card cage is already available. The 81201 and 81210 DC electronic loads can be integrated into any VXIbus-based test system and have been a standard offering in the 8100i Family of automatic power supply test systems from NH Research.

HIGHER POWER APPLICATIONS

Although rated at 50W continuous power, the 81201 and 81210 DC electronic loads can be used at considerably higher ratings. Since most testing is carried out at substantially less than continuous full power, analog control circuitry is used to monitor internal conditions and permit the DC load to extend its power handling capability with decreasing duty-cycles. Because the monitoring is real-time, the protection circuitry is tripped only if the DC load is in danger of being damaged. This allows testing for short periods or at low duty-cycles at power levels in excess of the steady state specifications. If continuous higher-than-rated power is required, two or more electronic loads may be operated in parallel.

PROGRAMMABLE TRANSIENT RESPONSE

The 81201 and 81210 DC electronic loads offer programmable transient response. Programmable rise-times permit the dynamic characteristics of the load to more closely approximate the operational conditions in which the unit-under-test (UUT) will be expected to function. In applications requiring testing under complex loading profiles, an analog input is provided which allows external control of the DC load current over the load's full operating range. Using an arbitrary waveform generator, almost any required loading profile can be realized.

GLITCH-FREE TRANSITIONS

Some UUT's such as switching power supplies must be turned on into a constant-resistance load before testing with a constant-current load can begin. The 81201 and 81210 DC electronic loads provide a glitch-free transition from one mode to another; the UUT does not see the load current fall to zero during the mode transition. In the short-circuit mode of operation, an SCR in parallel with the shorting relay is used to give a fast, low-resistance short.

ADVANCE PROTECTION AND CALIBRATION

The DC loads are fully protected against various fault conditions including over-voltage, reverse-voltage, over-current, over-power and over-temperature. All calibration and configuration data is stored in an EE-PROM, resulting in fast, internal "no pots" calibration of setting and metering values. The result is a rugged, highly reliable DC electronic load that requires minimal maintenance.

NH Research Products-Power Supply Test Systems & Electronic Loads

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