AC Sensors with DC Voltage Output

Our standard line of AC current and AC voltage sensors with DC output are designed for microprocessor or computer interfacing between the electrical processes and the controller.

Our high linearity current sensors can monitor from 2 to 600 amps, or as low as 100 mA with additional windings through the sensor hole. These sensors are current to voltage converters, and the output is calibrated to provide 5 VDC at full scale customer specified current (10 VDC output available by special order). The flux surrounding the wire being monitored supplies power to the sensor but requires much less power than a CT. The sensors magnetic air-gap prevents saturation at high current and exhibits a monotonic transition into the overload region. The air-gap also eliminates dangerous conditions associated with open secondary windings of CT's. These sensors come packaged in our "C", "D", and "E" case sizes. Case size will depend on wire diameter and the amount of current being monitored. You may also specify the type of connections you would like installed on the output of the sensor (lug nuts, solder terminals, wire, etc).

Our voltage sensors will monitor from 30 to 1000 Vrms. We use a transformer which has been optimized with external circuitry for the sensing of potential while drawing a minimum of power. Typically these units will draw less than 2 mA from the voltage being monitored. The transformer is also air-gapped so that large voltage excursions as well as transient phenomena are accommodated. The output of the voltage sensor is calibrated to provide 5 VDC at full scale customer specified voltage and isolated from the line. The unit comes packaged in our standard "D" size case.

We also manufacture current sensors with a 4/20 mA output . The output is always proportional to the current being monitored with 4 mA output at no current and 20 mA output at customer specified full-scale current. These sensors give a current output that can drive a 2 wire line over long distances with good accuracy in a noisy environment. The 4/20 does require an external DC power supply in the 16 to 45 VDC range to operate. A wiring diagram (in .pdf format) is avalible for downloading to show how the 4/20 is connected. You will need Adobe Acrobat Reader, which is freeware, to open this file. Our 4/20's come packaged in our Two Terminal case, "D" case, or "E" case, depending on the amount of current being monitored.

Applications include: Features include:
  • Computer Input
  • Motor Protection
  • Data Acquisition
  • Energy Management Control Systems (EMCS)
  • Power Measurement, Analysis, and Control
  • Fault Detection
  • Temperature Control by Current Monitoring
  • Servomechanism Control Systems
  • Building Control Systems (BCS)
  • Machine or Load Control through Current Sensing
  • Safety Switching
  • Process Control
  • Building power sharing: Multiple tenants, individual computer readout systems.
  • No additional power source needed (except 4/20 mA output).
  • Safe operation.
  • Extremely low burden.
  • Recommended use to several times F.S. rating. (Depends upon F.S. range)
  • Magnetic assemblies operate into open circuits, or may be loaded as needed for linearity desired.
  • No zero offset adjustment required.
  • Highly linear.
  • Proportional readout for computer interface.
  • Input intelligence for instrumentation.
  • Economical and flexible design solutions for monitoring and controlling.
  • Repeatable and accurate.
  • Fast response for statistically reliable sampling rates.

Here's another application using an SRT current sensor with DC output. We have designed a circuit which presents an operator with three lamps to indicate different power levels of a motor being used for various types of power tools (drill presses, table saws, etc). Because running current depends on the mechanical loading of the tool, it is possible to identify operations which feed work too fast or are being attempted with a dull bit. Green indicates that the motor is running at low load. Yellow indicates that the load is acceptable - the work is being fed at an optimal rate. Red indicates that the motor is being overloaded - the tool is dull or the work is being fed too fast. No light indicates that the motor is off and is useful when the hearing impaired need consideration. For schematic and circuit operation download our Three Lamp .PDF file. To open this file you will need Adobe Acrobat Reader. If you do not have Adobe Reader, it's freeware you can download to your computer from their internet site at

Engineers at SRT are available to discuss any questions you might have on any of our products. Often we are asked to customize or prepare special calibrations on our sensors to suit customer needs. Please contact us at (800) 447-6805 and ask for Dayle Smith or Doug McNutt, or FAX us at (719) 634-2601, or send E-mail to

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Product Information Listing:
[AC Voltage Output] [Current Actuated Switch] [Voltage Actuated Switch]
[Smart Power Measuring Sensor] [Clamp-on Current Sensor] [Battery Voltage Monitor]