The Sorensen SL Series of electronic loads are not only a great value, they are available in a wide variety of configurations, making them one of the most flexible electronic loads on the market. Models are available that provide both AC and DC loads, with input power ranging from 75 W to 1,800 W, and they are available in benchtop, modular and standalone form factors.

As you know, testing can be a precarious proposition. Device under test (DUT) failures can lead to abnormal operating conditions that can damage test equipment. To prevent this from happening to your electronic loads, the SL Series has five protection mechanisms:

• Over-voltage
• Over-current
• Over-power
• Over-temperature
• Reverse polarity

Over-voltage protection (OVP)

The over-voltage protection circuit is set at 63 V for all SL-series electronic loads. This voltage is not settable by the user. Should the voltage at the input terminals exceed 63 V, the over-voltage condition is triggered, and the device under test is internally disconnected from the load. When an over-voltage condition is triggered, the upper five-character display indicates "Prot," and the lower five-character display indicates "oVP".

Note that you should never apply an AC line voltage to your load. This can damage the load. The OVP circuit does not protect against severe over voltage conditions, and voltages above 100 V will permanently damage the electronic load, requiring factory repair.

Over-current protection (OCP)

The SL Series loads monitor the load current, and should the current measured be higher than 102% of programmed current, the load will turn itself off. When the over-current condition is triggered, the upper five-character display indicates "Prot," and the lower five-character display indicates "oCP".

Over Power Protection (OPP)

The SL Series loads also monitor the power dissipation of the load module, and should the power dissipation reach a level greater than 102% of programmed power input, the load will turn itself off. When the over-power condition is triggered, the upper five-character display indicates "Prot," and the lower five-character display indicates "oPP".

Over Temperature Protection (OTP)

The SL Series loads have temperature sensors on the heat sinks internal to the unit. If the temperature of the module's heat sink rises to greater than 90° C, the load turns itself off, and the over-temperature protection is triggered, and the upper five-character display indicates "Prot," and the lower five-character display indicates "otP." The unit will remain off until until the heat sink temperature drops to 70° C or below.

Quite often, an over-temperature condition is the result of poor ventilation. Check the environmental requirements spelled out in the operation manual and ensure that the distance between the rear panel of load mainframe and wall is greater than 15 cm.

Reverse polarity protection

The SL Series conducts reverse current when the polarity of the DC source connection is incorrect. If the reverse current exceeds the maximum reverse current, the unit will turn itself off and the upper five-character display indicates "Prot," and the lower five-character display indicates "-V", a negative current reading. Whenever a reverse current reading is displayed, turn OFF the DC power source immediately and make the correct connections.

For more information about input protection of the Sorensen SL Series, or about electronic loads in general, please contact AMETEK Programmable Power by sending email to sales.ppd@ametek.com or phoning 800-733-5427.