Frequently Asked Questions

What is the main difference between the SCT and UCT series and a 5 Amp output transformer (current-to-current)?

The 5 amp current-to-current:

  • Requires a resistive network provided by the customer to convert the current to a usable voltage
  • Can not operate output above 5 amps without heating and other performance issues
  • The 0.333 Voltage output SCT and UCT:

  • Burden resistor is already installed in the current sensor
  • Can be operated at several times the rated primary current without over-heating or other performance issues

Do you have distributors outside of the United States?

At this time Open Source Meter Inc does not have distributors outside of the United States.

Can an SCT-0750-005 Current Sensor be used on a 30, 50 or even 200 Amp circuit?

Magnelab SCT-0750 Current Transformers can function safely from zero to 200 Amps. A 5 Amp unit will have an output of 0.333 Volt at 5 Amps and the same unit used at 200 Amps will have an ideal output of 13.33 Volts. The temperature rise at 200 Amps will be only a few degrees due to low current in the secondary winding. Therefore, an SCT-0750-005 (5 Amp unit) could be used at 200 Amps since the core does not saturate and the temperature increase is minimal.

Where can I direct a technical question?

Technical questions may asked by calling 1-866-458-5528 or emailing Your question will be answered by a qualified engineer as promptly as possible.

What is the temperature range for the SCT and UCT products?

  • Operating Temperature Range: -10 to 55 deg C
  • Storage Temperature Range: -40 to 70 deg C

What are the actual weights of each of the SCT sizes?

Can I use the SCT and UCT series in an outdoor environment?

The SCT and UCT series are not designed for outdoor use.

What is the maximum length of black and white lead wires?

The current passing through the standard lead wires of our current sensors is very low, therefore, there is insignificant voltage drop due to the length of lead wires. In practice, the units have been tested up to 7,500 feet and the output voltage and phase angle shift were within the listed specifications.

What is the linearity of your Current Sensors?

                                         Our current sensors provide an output voltage proportional to the current input. For example, the SCT-1250-600 will have an output of 0.111 Volt at 200 Amps, and 0.333 Volt at 600 Amps, and output of 0.444 Volt at 800 Amps. We guaranty that the actual (measured) output voltage will be within one percent of calculated output voltage from 10% to 130% of rated current (from 60 Amps to 780 Amps).

Are these “metering grade” transformers?

All transformers in the SCT and UCT series are UL recognized and rated for an accuracy of ± 1% when used between 10% and 130% of the rated current.